CoordinatorLayout问题汇总

如果你只打算学习一下CoordinatorLayout然后写2个Demo试试，那么本文并没有什么卵用，但是如果你打算在生产环境使用CoordinatorLayout，那么强烈推荐阅读一下本文，可以减少很多弯路，这个东西看起来很好，但是实际上坑也很多。

###前言

很多应用主页常见的构造模式

一个包含ActionBar和Banner的header+ViewPager的组合模式

比如这样：





然后需要滚动的时候能够将 ActionBar和Banner滚出界面，但是又需要ViewPager的TabLayout能固定在屏幕顶部

比如滚动后是这样：





Github上有很多sticky-viewpager xx-header-viewpager之类的项目提供类似的功能，但是大部分都会存在各种事件冲突问题，比如滑动不流畅，卡顿，弹跳之类的。

好在Android新的SupportLibrary提供了CoordinatorLayout能直接实现类似功能，具体如何使用参考 SupportLibrary中CoordinatorLayout的使用文档即可，例子也可以直接看cheesesquare

我就谈下使用过程中里面的坑：

不支持ListView,不支持ScrollView，低版本不兼容ViewCompat.setNestedScrollingEnabled

PS.更新

support 23.1+新增了

ViewCompat.setNestedScrollingEnabled(listView/gridview,true);

可以给ListView提供NestedScrolling支持,但是只在LOLIPOP+版本上生效，下面的方案也一样。

低版本只能使用RecyclerView

一些文档/博客文章上说 可以使用一个 可滚动的组件

还有些错误的文章说 支持ListView

实际上该组件必须实现了 NestedScrollingChild接口

你可以使用RecyclerView,RecyclerView自身就实现了该接口，如果你要使用其他组件，那么可能需要继承原来的View并实现NestedScrollingChild接口

一个实现了NestedScrollingChild的Listview demo如下：

public class NestedScrollingListView extends ListView implements NestedScrollingChild {

private final NestedScrollingChildHelper mScrollingChildHelper;

public NestedScrollingListView(Context context) {
super(context);
mScrollingChildHelper = new NestedScrollingChildHelper(this);
setNestedScrollingEnabled(true);
}

public NestedScrollingListView(Context context, AttributeSet attrs) {
super(context, attrs);
mScrollingChildHelper = new NestedScrollingChildHelper(this);
setNestedScrollingEnabled(true);
}

@Override
public void setNestedScrollingEnabled(boolean enabled) {
mScrollingChildHelper.setNestedScrollingEnabled(enabled);
}

@Override
public boolean isNestedScrollingEnabled() {
return mScrollingChildHelper.isNestedScrollingEnabled();
}

@Override
public boolean startNestedScroll(int axes) {
return mScrollingChildHelper.startNestedScroll(axes);
}

@Override
public void stopNestedScroll() {
mScrollingChildHelper.stopNestedScroll();
}

@Override
public boolean hasNestedScrollingParent() {
return mScrollingChildHelper.hasNestedScrollingParent();
}

@Override
public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed,
int dyUnconsumed, int[] offsetInWindow) {
return mScrollingChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed,
dxUnconsumed, dyUnconsumed, offsetInWindow);
}

@Override
public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
return mScrollingChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);
}

@Override
public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
return mScrollingChildHelper.dispatchNestedFling(velocityX, velocityY, consumed);
}

@Override
public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
return mScrollingChildHelper.dispatchNestedPreFling(velocityX, velocityY);
}
}

其他View也可以使用类似的方式实现。

只对 5.0+ 生效，低版本无效。

RecyclerView滑动的时候不流畅

目前已知 r23.1 & r 23.2 都存在此问题，Google code的提交代码里倒是有相关修复记录，但是目前还没有发布。

直接原因是Fling Direction错误，导致Fling事件被吃掉了，ACTION_UP/ACTION_CANCEL事件一旦发生，scroll动作直接停止

StackOverFlow上一个高票解决方案是重写一个FlingBehavior，并配置给AppBar.

注意，这个Behavior是给AppBar的，不是给下面的可滚动组件的。

<android.support.design.widget.AppBarLayout
android:id="@+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_behavior="your.package.FlingBehavior">
<!--your views here-->
</android.support.design.widget.AppBarLayout>

public class FlingBehavior extends AppBarLayout.Behavior {

private static final int TOP_CHILD_FLING_THRESHOLD = 3;
private boolean isPositive;

public FlingBehavior() {
}

public FlingBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}

@Override
public boolean onNestedFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY, boolean consumed) {
if (velocityY > 0 && !isPositive || velocityY < 0 && isPositive) {
velocityY = velocityY * -1;
}
if (target instanceof RecyclerView && velocityY < 0) {
final RecyclerView recyclerView = (RecyclerView) target;
final View firstChild = recyclerView.getChildAt(0);
final int childAdapterPosition = recyclerView.getChildAdapterPosition(firstChild);
consumed = childAdapterPosition > TOP_CHILD_FLING_THRESHOLD;
}
consumed=false;
return super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
}

@Override
public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, int dx, int dy, int[] consumed) {
super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed);
isPositive = dy > 0;
}

注意consumed计算这部分，会影响滚动形式

请参考父类滚动的实现代码：

@Override
public boolean onNestedFling(final CoordinatorLayout coordinatorLayout,
final AppBarLayout child, View target, float velocityX, float velocityY,
boolean consumed) {
boolean flung = false;

if (!consumed) {
// It has been consumed so let's fling ourselves
flung = fling(coordinatorLayout, child, -child.getTotalScrollRange(),
0, -velocityY);
} else {
// If we're scrolling up and the child also consumed the fling. We'll fake scroll
// upto our 'collapsed' offset
if (velocityY < 0) {
// We're scrolling down
final int targetScroll = -child.getTotalScrollRange()
+ child.getDownNestedPreScrollRange();
if (getTopBottomOffsetForScrollingSibling() < targetScroll) {
// If we're currently not expanded more than the target scroll, we'll
// animate a fling
animateOffsetTo(coordinatorLayout, child, targetScroll);
flung = true;
}
} else {
// We're scrolling up
final int targetScroll = -child.getUpNestedPreScrollRange();
if (getTopBottomOffsetForScrollingSibling() > targetScroll) {
// If we're currently not expanded less than the target scroll, we'll
// animate a fling
animateOffsetTo(coordinatorLayout, child, targetScroll);
flung = true;
}
}
}

mWasNestedFlung = flung;
return flung;
}

确认你需要滚动哪一步分，你可以简单根据RecyclerView展示的first item的position来判断Recyclerview是否在top位置，也有另一种代码如下：

@Override
public boolean onNestedFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY, boolean consumed) {
if (target instanceof RecyclerView) {
final RecyclerView recyclerView = (RecyclerView) target;
consumed = velocityY > 0 || recyclerView.computeVerticalScrollOffset() > 0;
}
return super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
}

另一个解决方案是使用 smooth-app-bar-layout

具体如何使用请参考它自己的文档

当header是Toolbar时，demo运作良好，当headerview高度较大时，滑动会发生剧烈抖动，弹跳，暂时还没去看它源代码，可能是我使用不正确

不支持adjustResize

可以参考这个问题
http://stackoverflow.com/questions/35599125/adjustresize-does-not-work-with-coordinatorlayout

解决方案是可以通过ViewTreeObserver.OnGlobalLayoutListener监听界面改变，然后人工处理padding bottom

public class KeyboardUtil {
private View decorView;
private View contentView;

public KeyboardUtil(Activity act, View contentView) {
this.decorView = act.getWindow().getDecorView();
this.contentView = contentView;

//only required on newer android versions. it was working on API level 19
if (Build.VERSION.SDK_INT >= 19) {
decorView.getViewTreeObserver().addOnGlobalLayoutListener(onGlobalLayoutListener);
}
}

public void enable() {
if (Build.VERSION.SDK_INT >= 19) {
decorView.getViewTreeObserver().addOnGlobalLayoutListener(onGlobalLayoutListener);
}
}

public void disable() {
if (Build.VERSION.SDK_INT >= 19) {
decorView.getViewTreeObserver().removeOnGlobalLayoutListener(onGlobalLayoutListener);
}
}

//a small helper to allow showing the editText focus
ViewTreeObserver.OnGlobalLayoutListener onGlobalLayoutListener = new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
Rect r = new Rect();
//r will be populated with the coordinates of your view that area still visible.
decorView.getWindowVisibleDisplayFrame(r);

//get screen height and calculate the difference with the useable area from the r
int height = decorView.getContext().getResources().getDisplayMetrics().heightPixels;
int diff = height - r.bottom;

//if it could be a keyboard add the padding to the view
if (diff != 0) {
// if the use-able screen height differs from the total screen height we assume that it shows a keyboard now
//check if the padding is 0 (if yes set the padding for the keyboard)
if (contentView.getPaddingBottom() != diff) {
//set the padding of the contentView for the keyboard
contentView.setPadding(0, 0, 0, diff);
}
} else {
//check if the padding is != 0 (if yes reset the padding)
if (contentView.getPaddingBottom() != 0) {
//reset the padding of the contentView
contentView.setPadding(0, 0, 0, 0);
}
}
}
};

/**
* Helper to hide the keyboard
*
* @param act
*/
public static void hideKeyboard(Activity act) {
if (act != null && act.getCurrentFocus() != null) {
InputMethodManager inputMethodManager = (InputMethodManager) act.getSystemService(Activity.INPUT_METHOD_SERVICE);
inputMethodManager.hideSoftInputFromWindow(act.getCurrentFocus().getWindowToken(), 0);
}
}
}

KeyboardUtil keyboardUtil = new KeyboardUtil(this, findViewById(android.R.id.content));

//enable it
keyboardUtil.enable();

ps.

fitSystemWindow 和 adjustResize 和 FLAG_TRANSLUCENT_STATUS 一起使用 一样也会有冲突，造成界面缩放不正常。 当时也是用的这个解决方案。

CoordinatorLayout的onScrollListener只支持21+

解决方案：

在Behavior里监听滚动，并把数据传出来

代码和后一个问题贴在一起

注意 我这里只监听了 onDependentViewChanged

并在这里调用onScroll接口，然后外部实际使用的数据是 headerview.getTop , 并不能覆盖全部情况，但是我本身只用来做状态栏渐变色，有其它使用场景请自行修改

当顶部容器不使用Toolbar时，Measure会有问题

解决方案：

自定义一个 Behavior,继承AppBarLayout.ScrollingViewBehavior

并重载onMeasureChild方法

public class PatchedScrollingViewBehavior extends AppBarLayout.ScrollingViewBehavior {

private OnScrollListener onScrollListener;

public PatchedScrollingViewBehavior() {
super();
}

public PatchedScrollingViewBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}

@Override
public boolean onMeasureChild(CoordinatorLayout parent, View child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed) {

Log.e("####", "onMeasureChild");

if (child.getLayoutParams().height == -1) {
List dependencies = parent.getDependencies(child);
if (dependencies.isEmpty()) {
return false;
}

AppBarLayout appBar = findFirstAppBarLayout(dependencies);
if (appBar != null && ViewCompat.isLaidOut(appBar)) {
if (ViewCompat.getFitsSystemWindows(appBar)) {
ViewCompat.setFitsSystemWindows(child, true);
}

int scrollRange = appBar.getTotalScrollRange();
//                int height = parent.getHeight() - appBar.getMeasuredHeight() + scrollRange;
int parentHeight = View.MeasureSpec.getSize(parentHeightMeasureSpec);
int height = parentHeight - appBar.getMeasuredHeight() + scrollRange;
int heightMeasureSpec = View.MeasureSpec.makeMeasureSpec(height, View.MeasureSpec.AT_MOST);
parent.onMeasureChild(child, parentWidthMeasureSpec, widthUsed, heightMeasureSpec, heightUsed);
return true;
}
}

return false;
}

@Override
public void onNestedScroll(CoordinatorLayout coordinatorLayout, View child, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);
}

private static AppBarLayout findFirstAppBarLayout(List<View> views) {
int i = 0;
for (int z = views.size(); i < z; ++i) {
View view = (View) views.get(i);
if (view instanceof AppBarLayout) {
return (AppBarLayout) view;
}
}
return null;
}

@Override
public boolean onDependentViewChanged(CoordinatorLayout parent, View child,
View dependency) {
if (onScrollListener != null) {
onScrollListener.onScroll(parent, child, dependency);
}
return super.onDependentViewChanged(parent, child, dependency);
}

public interface OnScrollListener {
void onScroll(CoordinatorLayout parent, View child,
View dependency);

}

public OnScrollListener getOnScrollListener() {
return onScrollListener;
}

public void setOnScrollListener(OnScrollListener onScrollListener) {
this.onScrollListener = onScrollListener;
}
}

REF:
http://stackoverflow.com/questions/30923889/flinging-with-recyclerview-appbarlayout
https://github.com/henrytao-me/smooth-app-bar-layout
https://code.google.com/p/android/issues/detail?id=177729