让 Toolbar 随着 RecyclerView 的滚动而显示/隐藏(Part 1)
2016-08-09 09:45
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这篇文章是过时的,你应该跳到第三部分 3。
在这篇文章中,我们将看到如何实现像Google+ 应用程序一样,当列表下滑时,Toolbar和FAB(包括其他的View)隐藏;当列表上滑时,Toolbar和FAB(包括其他的View)显示的效果;这种效果在Material
Design Checklist提到过.
“在一些场景下,当屏幕向上滚动时,app bar将会从屏幕上移除,留出更多的空间供内容。相反,当向上滚动时,app bar应再次显示。
我们的目标效果如下图所示:
我们将使用
给List设置padding
给List添加一个headr
我只是决定执行第二个方案,因为我发现在如何给
我也将简要描述第一个。
我们要创建一个工程,并添加如下依赖:
现在我们应该定义
接下来是创建
这是一个简单的布局,只有
让我们来看看
正如你所看到的,这是一个十分简单的类,它只实现onCreate()方法,做了以下事情:
初始化
获取FAB
初始化
现在我们将为
对应的
我们的列表用于呈现带有文本的卡片 - 简单吧!
现在,我们看一下
这个是
Allison的文章
我们写好以上代码,运行一下!截图如下:
等一下,那是什么?你注意到没有?
这样做,可以达到效果。但是,我想告诉你另一种实现方式-也许有点复杂,涉及增加了头的列表。
首先,我们需要对Adapter做一些更改:
代码的具体思路如下:
我们需要为
Type。而这正是我们想要做的,我们的第一个Item将是一个标题视图,不同于其他的项目(lines 3-4).
我们需要告诉
我们需要修改
14-34).
我们需要修改
布局很简单。重要的是要注意的是,它的高度需要是等于
好了,我们完成了!截图如上:
好多了,对吗?所以,综上所述,我们需要为RecyclerView增加了一个Header。它和Toolbar高度相同,它是一个空视图。toolbar刚好将其挡住,而其他的视图可以恰当好处的显示。接下来我们可以实现列表滚动时显示/隐藏视图。
为了实现这个效果,我们将为
真正起到作用的方法就是你现在看到的方法
基本的实现思路如下:
我们计算总的滚动距离(每一次滚动的总和)。但是,我们只关心View隐藏时的向上滑动或者View显示时的向下滑动,因为这些是我们所关心的场景。
if((controlsVisible && dy>0) || (!controlsVisible && dy<0)) {
scrolledDistance += dy;
}
如果当滚动值超过某个阈值(你可以设置的值越大,需要滚动滚动更多的距离,才能看到显示/隐藏View的效果)。我们根据滚动的方向来显示/隐藏View(DY>0意味着我们向下滚动,Dy<0意味着我们滚动起来)。
if (scrolledDistance > HIDE_THRESHOLD && controlsVisible) {
onHide();
controlsVisible = false;
scrolledDistance = 0;
} else if (scrolledDistance < -HIDE_THRESHOLD && !controlsVisible) {
onShow();
controlsVisible = true;
scrolledDistance = 0;
}
事实上,我们不可能在Scroll Listener中显示/隐藏View,更为靠谱的做法是,将其抽象出来,调用show()/hide()方法,所以我们需要在回调中实现它们。
现在,我们需要给
添加下面的方法,可以以动画的形式隐藏或显示View:
我们必须把margin作为隐藏Toolbar的参数,否则就不能完全隐藏Fab。
是时候看一下我们的应用程序的效果了!滚动屏幕截图
它看起来挺不错的,但是有一些小细节需要调整 - 如果你处于列表的顶部,而滑动隐藏的阈值设置的很小,那么即使在列表为空的情况下,你也可以隐藏
更改以后,当第一项是可见的时候,Header不会消失。接着向下滑的时候,其他的效果还是和之前的一样再次运行我们的项目,实际效果如下:
Yup! 现在看上去很不错哦!
这是我第一次写的博客,所以可能存在着一些错误,以后我会有所提高的。
And if you don’t want to use the method with adding a header, you can still use the second one with adding padding to the
Just add the padding and use
如果你不想添加Head的方法,你仍然可以使用第二个加垫的
在下一个部分,我将告诉你如何做出像Google Play一样的效果。
如果你有什么疑问,你可以在下面的评论区评论。
这篇文章提到的所有源代码,你都可以在对应的Github仓库上找到.
感谢Mirek Stanek作为这篇文章的内测读者.
Michał Z.
如果你喜欢这篇文章,你可以把他分享给你的关注者 或者在Twitter关注我!
转自:http://blog.csdn.net/u012548313/article/details/50453891
在这篇文章中,我们将看到如何实现像Google+ 应用程序一样,当列表下滑时,Toolbar和FAB(包括其他的View)隐藏;当列表上滑时,Toolbar和FAB(包括其他的View)显示的效果;这种效果在Material
Design Checklist提到过.
“在一些场景下,当屏幕向上滚动时,app bar将会从屏幕上移除,留出更多的空间供内容。相反,当向上滚动时,app bar应再次显示。
我们的目标效果如下图所示:
我们将使用
RecyclerView为我们的List,当然,你也可以选择其他滚动控件(例如
ListView,但它就意味着更多的编码。现在,我有两种具体的实现方法:
给List设置padding
给List添加一个headr
我只是决定执行第二个方案,因为我发现在如何给
RecyclerView添加header这一问题上,有很多需要注意的地方,这是一个很好的机会去解决他们。
我也将简要描述第一个。
我们开始吧
我们要创建一个工程,并添加如下依赖:<code class="hljs rust has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"> dependencies { compile fileTree(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">dir</span>: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'libs'</span>, include: [<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'*.jar'</span>]) compile <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'com.android.support:appcompat-v7:21.0.3'</span> compile <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"com.android.support:recyclerview-v7:21.0.0"</span> compile <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'com.android.support:cardview-v7:21.0.3'</span> }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li></ul>
现在我们应该定义
style.xml,我们的应用程序将使用Material的主题,但我们不使用
ActionBar(取而代之是
Toolbar):
<code class="hljs applescript has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><style <span class="hljs-property" style="box-sizing: border-box;">name</span>=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"AppTheme"</span> parent=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Theme.AppCompat.Light.NoActionBar"</span>> <<span class="hljs-property" style="box-sizing: border-box;">item</span> <span class="hljs-property" style="box-sizing: border-box;">name</span>=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"colorPrimary"</span>>@color/color_primary</<span class="hljs-property" style="box-sizing: border-box;">item</span>> <<span class="hljs-property" style="box-sizing: border-box;">item</span> <span class="hljs-property" style="box-sizing: border-box;">name</span>=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"colorPrimaryDark"</span>>@color/color_primary_dark</<span class="hljs-property" style="box-sizing: border-box;">item</span>> </style></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>
接下来是创建
Activity的布局:
<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><FrameLayout xmlns:android=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"http://schemas.android.com/apk/res/android"</span> android:layout_width=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"match_parent"</span> android:layout_height=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"match_parent"</span>> <android<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.support</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.v</span>7<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.widget</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.RecyclerView</span> android:id=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"@+id/recyclerView"</span> android:layout_width=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"match_parent"</span> android:layout_height=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"match_parent"</span>> <android<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.support</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.v</span>7<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.widget</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Toolbar</span> android:id=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"@+id/toolbar"</span> android:layout_width=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"match_parent"</span> android:layout_height=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"?attr/actionBarSize"</span> android:background=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"?attr/colorPrimary"</span>> <ImageButton android:id=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"@+id/fabButton"</span> android:layout_width=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"56dp"</span> android:layout_height=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"56dp"</span> android:layout_gravity=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"bottom|right"</span> android:layout_marginbottom=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"16dp"</span> android:layout_marginright=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"16dp"</span> android:background=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"@drawable/fab_background"</span> android:src=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"@drawable/ic_favorite_outline_white_24dp"</span> android:contentdescription=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"@null"</span>> </ImageButton> </android<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.support</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.v</span>7<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.widget</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Toolbar</span>> </android<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.support</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.v</span>7<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.widget</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.RecyclerView</span>> </FrameLayout></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li></ul>
这是一个简单的布局,只有
RecyclerView、
Toolbar以及作为FAB的
ImageButton。我们需要把它们放在一个
FrameLayout,因为这样可以达到
Toolbar覆盖
RecyclerView的效果。如果我们不这样做,当我们隐藏Toolbar的时候在列表的上方将会有一个空白的空间。
让我们来看看
MainActiviy的代码吧:
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">MainActivity</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">ActionBarActivity</span> {</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> Toolbar mToolbar; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> ImageButton mFabButton; <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onCreate</span>(Bundle savedInstanceState) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.onCreate(savedInstanceState); setContentView(R.layout.activity_main); initToolbar(); mFabButton = (ImageButton) findViewById(R.id.fabButton); initRecyclerView(); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">initToolbar</span>() { mToolbar = (Toolbar) findViewById(R.id.toolbar); setSupportActionBar(mToolbar); setTitle(getString(R.string.app_name)); mToolbar.setTitleTextColor(getResources().getColor(android.R.color.white)); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">initRecyclerView</span>() { RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerView); recyclerView.setLayoutManager(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> LinearLayoutManager(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>)); RecyclerAdapter recyclerAdapter = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> RecyclerAdapter(createItemList()); recyclerView.setAdapter(recyclerAdapter); } }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li></ul>
正如你所看到的,这是一个十分简单的类,它只实现onCreate()方法,做了以下事情:
初始化
Toolbar
获取FAB
初始化
RecyclerView
现在我们将为
RecylerView创建adapter。在这之前,我们需要添加list item的布局:
<code class="hljs xml has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-pi" style="color: rgb(0, 102, 102); box-sizing: border-box;"><?xml version="1.0" encoding="utf-8"?></span> <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">android.support.v7.widget.cardview </span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">xmlns:android</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"http://schemas.android.com/apk/res/android"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">xmlns:card_view</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"http://schemas.android.com/apk/res-auto"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_width</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"match_parent"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_height</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"wrap_content"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_gravity</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"center"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_margin</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"8dp"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">card_view:cardcornerradius</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"4dp"</span>></span> <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">TextView </span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:id</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"@+id/itemTextView"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_width</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"match_parent"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_height</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"?attr/listPreferredItemHeight"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:gravity</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"center_vertical"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:padding</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"8dp"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">style</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"@style/Base.TextAppearance.AppCompat.Body2"</span>></span> <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">TextView</span>></span> <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">android.support.v7.widget.cardview</span>></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li></ul>
对应的
ViewHolder如下:
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">RecyclerItemViewHolder</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">RecyclerView</span>.<span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">ViewHolder</span> {</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> TextView mItemTextView; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">RecyclerItemViewHolder</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> View parent, TextView itemTextView) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>(parent); mItemTextView = itemTextView; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> RecyclerItemViewHolder <span class="hljs-title" style="box-sizing: border-box;">newInstance</span>(View parent) { TextView itemTextView = (TextView) parent.findViewById(R.id.itemTextView); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> RecyclerItemViewHolder(parent, itemTextView); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">setItemText</span>(CharSequence text) { mItemTextView.setText(text); } }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li></ul>
我们的列表用于呈现带有文本的卡片 - 简单吧!
现在,我们看一下
RecyclerAdapter的代码:
<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> RecyclerAdapter extends RecyclerView.Adapter<recyclerview.viewholder> { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> List<<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>> mItemList; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">RecyclerAdapter</span>(List<<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>> itemList) { mItemList = itemList; } @Override <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> RecyclerView.ViewHolder <span class="hljs-title" style="box-sizing: border-box;">onCreateViewHolder</span>(ViewGroup parent, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> viewType) { final View view = LayoutInflater.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">from</span>(parent.getContext()).inflate(R.layout.recycler_item, parent, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> RecyclerItemViewHolder.newInstance(view); } @Override <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onBindViewHolder</span>(RecyclerView.ViewHolder viewHolder, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> position) { RecyclerItemViewHolder holder = (RecyclerItemViewHolder) viewHolder; String itemText = mItemList.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">get</span>(position); holder.setItemText(itemText); } @Override <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">getItemCount</span>() { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> mItemList == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> ? <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span> : mItemList.size(); } }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li></ul>
这个是
RecyclerView.Adapter的基本实现。并没有什么特殊的东西。如果,你想深入了解
RecyclerView,我建议你好好的阅读一下Mark
Allison的文章
我们写好以上代码,运行一下!截图如下:
等一下,那是什么?你注意到没有?
Toolbar把我们的列表挡住了。那是因为我们在
activity_main.xml中设置
FrameLayout为根布局。在开始的时候,我们提到过,这里有两种解决方案。第一张就是给
RecyclerView设置paddingTop,其高度和
Toolbar保持一致。但是还有一些细节需要注意,因为默认情况下,控件的绘制区域是在padding里面的,所以我们需要将其关闭,具体代码如下:
<android.support.v7.widget.recyclerview android:id="@+id/recyclerView" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingtop="?attr/actionBarSize" android:cliptopadding="false" </android.support.v7.widget.recyclerview>
这样做,可以达到效果。但是,我想告诉你另一种实现方式-也许有点复杂,涉及增加了头的列表。
为RecyclerView
添加Header
首先,我们需要对Adapter做一些更改:<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> RecyclerAdapter extends RecyclerView.Adapter<recyclerview.viewholder> { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//added view types</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> final <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> TYPE_HEADER = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> final <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> TYPE_ITEM = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> List<<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>> mItemList; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">RecyclerAdapter</span>(List<<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>> itemList) { mItemList = itemList; } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//modified creating viewholder, so it creates appropriate holder for a given viewType</span> @Override <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> RecyclerView.ViewHolder <span class="hljs-title" style="box-sizing: border-box;">onCreateViewHolder</span>(ViewGroup parent, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> viewType) { Context context = parent.getContext(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (viewType == TYPE_ITEM) { final View view = LayoutInflater.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">from</span>(context).inflate(R.layout.recycler_item, parent, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> RecyclerItemViewHolder.newInstance(view); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (viewType == TYPE_HEADER) { final View view = LayoutInflater.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">from</span>(context).inflate(R.layout.recycler_header, parent, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> RecyclerHeaderViewHolder(view); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> RuntimeException(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"There is no type that matches the type "</span> + viewType + <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">" + make sure your using types correctly"</span>); } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//modifed ViewHolder binding so it binds a correct View for the Adapter</span> @Override <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onBindViewHolder</span>(RecyclerView.ViewHolder viewHolder, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> position) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!isPositionHeader(position)) { RecyclerItemViewHolder holder = (RecyclerItemViewHolder) viewHolder; String itemText = mItemList.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">get</span>(position - <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// we are taking header in to account so all of our items are correctly positioned</span> holder.setItemText(itemText); } } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//our old getItemCount()</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">getBasicItemCount</span>() { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> mItemList == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> ? <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span> : mItemList.size(); } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//our new getItemCount() that includes header View</span> @Override <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">getItemCount</span>() { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> getBasicItemCount() + <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>; <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// header</span> } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//added a method that returns viewType for a given position</span> @Override <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">getItemViewType</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> position) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (isPositionHeader(position)) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> TYPE_HEADER; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> TYPE_ITEM; } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//added a method to check if given position is a header</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> boolean <span class="hljs-title" style="box-sizing: border-box;">isPositionHeader</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> position) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> position == <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; } }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li></ul>
代码的具体思路如下:
我们需要为
Recycler展示的不同的Item定义不同的Item Type。
RecyclerView是一个非常灵活的组件。当您希望为您的列表项目有不同的布局时,可以使用Item
Type。而这正是我们想要做的,我们的第一个Item将是一个标题视图,不同于其他的项目(lines 3-4).
我们需要告诉
Recycler,返回哪个类型用于显示(lines 49-54).
我们需要修改
onCreateViewHolder和
onBindViewHolder方法,根据type的不同TYPE_ITEM或者TYPE_HEAD,返回相应的item(lines
14-34).
我们需要修改
getItemCount()- 返回的总数为数据集总数 + 1,因为我们还有一个Header(line 43-45)。现在,我们创建一个布局,并为其添加一个
ViewHolder。
<code class="hljs xml has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"> <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">view</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">xmlns:android</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"http://schemas.android.com/apk/res/android"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_width</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"match_parent"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_height</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"?attr/actionBarSize"</span>></span> <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">view</span>></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>
布局很简单。重要的是要注意的是,它的高度需要是等于
Toolbar的高度。这是
viewholder,也很简单:
public class RecyclerHeaderViewHolder extends RecyclerView.ViewHolder { public RecyclerHeaderViewHolder(View itemView) { super(itemView); } }
好了,我们完成了!截图如上:
好多了,对吗?所以,综上所述,我们需要为RecyclerView增加了一个Header。它和Toolbar高度相同,它是一个空视图。toolbar刚好将其挡住,而其他的视图可以恰当好处的显示。接下来我们可以实现列表滚动时显示/隐藏视图。
在列表滚动的时候显示/隐藏View
为了实现这个效果,我们将为RecyclerView创建一个类
onscrolllistener。
public abstract class HidingScrollListener extends RecyclerView.OnScrollListener { private static final int HIDE_THRESHOLD = 20; private int scrolledDistance = 0; private boolean controlsVisible = true; @Override public void onScrolled(RecyclerView recyclerView, int dx, int dy) { super.onScrolled(recyclerView, dx, dy); if (scrolledDistance > HIDE_THRESHOLD && controlsVisible) { onHide(); controlsVisible = false; scrolledDistance = 0; } else if (scrolledDistance < -HIDE_THRESHOLD && !controlsVisible) { onShow(); controlsVisible = true; scrolledDistance = 0; } if((controlsVisible && dy>0) || (!controlsVisible && dy<0)) { scrolledDistance += dy; } } public abstract void onHide(); public abstract void onShow(); }
真正起到作用的方法就是你现在看到的方法
onscrolled()方法。它的参数——dx,dy是水平和垂直滚动的量。其实他们是每次滑动的变化量,是两个前后事件的差,不是总滚动距离。
基本的实现思路如下:
我们计算总的滚动距离(每一次滚动的总和)。但是,我们只关心View隐藏时的向上滑动或者View显示时的向下滑动,因为这些是我们所关心的场景。
if((controlsVisible && dy>0) || (!controlsVisible && dy<0)) {
scrolledDistance += dy;
}
如果当滚动值超过某个阈值(你可以设置的值越大,需要滚动滚动更多的距离,才能看到显示/隐藏View的效果)。我们根据滚动的方向来显示/隐藏View(DY>0意味着我们向下滚动,Dy<0意味着我们滚动起来)。
if (scrolledDistance > HIDE_THRESHOLD && controlsVisible) {
onHide();
controlsVisible = false;
scrolledDistance = 0;
} else if (scrolledDistance < -HIDE_THRESHOLD && !controlsVisible) {
onShow();
controlsVisible = true;
scrolledDistance = 0;
}
事实上,我们不可能在Scroll Listener中显示/隐藏View,更为靠谱的做法是,将其抽象出来,调用show()/hide()方法,所以我们需要在回调中实现它们。
现在,我们需要给
RecyclerView设置listener:
private void initRecyclerView() { RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerView); recyclerView.setLayoutManager(new LinearLayoutManager(this)); RecyclerAdapter recyclerAdapter = new RecyclerAdapter(createItemList()); recyclerView.setAdapter(recyclerAdapter); //setting up our OnScrollListener recyclerView.setOnScrollListener(new HidingScrollListener() { @Override public void onHide() { hideViews(); } @Override public void onShow() { showViews(); } }); }
添加下面的方法,可以以动画的形式隐藏或显示View:
private void hideViews() { mToolbar.animate().translationY(-mToolbar.getHeight()).setInterpolator(new AccelerateInterpolator(2)); FrameLayout.LayoutParams lp = (FrameLayout.LayoutParams) mFabButton.getLayoutParams(); int fabBottomMargin = lp.bottomMargin; mFabButton.animate().translationY(mFabButton.getHeight()+fabBottomMargin).setInterpolator(new AccelerateInterpolator(2)).start(); } private void showViews() { mToolbar.animate().translationY(0).setInterpolator(new DecelerateInterpolator(2)); mFabButton.animate().translationY(0).setInterpolator(new DecelerateInterpolator(2)).start(); }
我们必须把margin作为隐藏Toolbar的参数,否则就不能完全隐藏Fab。
是时候看一下我们的应用程序的效果了!滚动屏幕截图
它看起来挺不错的,但是有一些小细节需要调整 - 如果你处于列表的顶部,而滑动隐藏的阈值设置的很小,那么即使在列表为空的情况下,你也可以隐藏
ToolBar.幸运的是,这个问题很容易解决。我们需要做的是检测列表的第一项是否是可见的,从而根据实际情况调整
ToolBar的显示/隐藏。
@Override public void onScrolled(RecyclerView recyclerView, int dx, int dy) { super.onScrolled(recyclerView, dx, dy); int firstVisibleItem = ((LinearLayoutManager) recyclerView.getLayoutManager()).findFirstVisibleItemPosition(); //show views if first item is first visible position and views are hidden if (firstVisibleItem == 0) { if(!controlsVisible) { onShow(); controlsVisible = true; } } else { if (scrolledDistance > HIDE_THRESHOLD && controlsVisible) { onHide(); controlsVisible = false; scrolledDistance = 0; } else if (scrolledDistance < -HIDE_THRESHOLD && !controlsVisible) { onShow(); controlsVisible = true; scrolledDistance = 0; } } if((controlsVisible && dy>0) || (!controlsVisible && dy<0)) { scrolledDistance += dy; } }
更改以后,当第一项是可见的时候,Header不会消失。接着向下滑的时候,其他的效果还是和之前的一样再次运行我们的项目,实际效果如下:
Yup! 现在看上去很不错哦!
这是我第一次写的博客,所以可能存在着一些错误,以后我会有所提高的。
And if you don’t want to use the method with adding a header, you can still use the second one with adding padding to the
RecyclerView.
Just add the padding and use
HidingScrollListenerthat we’ve just created and it will work :)
如果你不想添加Head的方法,你仍然可以使用第二个加垫的
recyclerview。只要加入我们刚刚创建的,它将填充和使用
hidingscrolllistener:)
在下一个部分,我将告诉你如何做出像Google Play一样的效果。
如果你有什么疑问,你可以在下面的评论区评论。
代码
这篇文章提到的所有源代码,你都可以在对应的Github仓库上找到.感谢Mirek Stanek作为这篇文章的内测读者.
Michał Z.
如果你喜欢这篇文章,你可以把他分享给你的关注者 或者在Twitter关注我!
转自:http://blog.csdn.net/u012548313/article/details/50453891
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