android布局参数详解

android线性布局参数详解

 

线性布局中，有
4
个及其重要的参数，直接决定元素的布局和位置，这四个参数是

android:layout_gravity
(
是本元素相对于父元素的重力方向
)

android:gravity

（是本元素所有子元素的重力方向）

android:orientation

（线性布局以列或行来显示内部子元素）

android:layout_weight

（线性布局内子元素对未占用空间【水平或垂直】分配权重值，其值越小，权重越大。

                            前提是子元素

设置了
android:layout_width

=

"fill_parent"

属性（水平方向）

                              

或
android:layout_height

=

"fill_parent"
属性（垂直方向）

如果某个子元素的

android:layout_width

=

"wrap_content"

          
或

android:layout_height
="

wrap_content”

，

则

android:layout_weight

的设置值
对该方向上空间的分配刚好相反。

 
下面以一个简单例子来说明这
4个参数


<?
xml

version
=
"1.0"

encoding
=
"utf-8"

?>

<
LinearLayout
xmlns:android
=
"http://schemas.android.com/apk/res/android"

                          
android:layout_height
=
"200dp"

                          
android:layout_width
=
"200dp"

                          
android:background
=
"#AABBCC"

                          
android:orientation=
"horizontal"

                          
android:layout_gravity=
"center"

>

                          
<
TextView

android:text
=
"ONE"

                                              
android:background
=
"#aa0000"

                                              
android:layout_height
=
"wrap_content"

                                              
android:layout_width
=
"wrap_content"

                                              
android:layout_margin
=
"1dp"

/>

                            <
TextView

android:text
=
"TWO"

                                              
android:background
=
"#aa0000"

                                              
android:layout_height
=
"wrap_content"

                                              
android:layout_width
=
"wrap_content"

                                              
android:layout_margin
=
"1dp"

/>

</

LinearLayout

>

 
说明：在上面的例子中，根布局是LinearLayout,
其包含有2
个TextView
视图，为了对参数

android:layout_gravity

有直观的了解，对根布局

LinearLayout

特意加了

3

个参数

android:layout_height

=

"200dp"

android:layout_width
 
=
"200dp"

android:background
   
=
"#AABBCC"

为布局指定了固定的宽度和高度，以及背景颜色，上面的例子运行后效果如下图：

 



 
说明：对LinearLayout
中的参数android:layout_gravity

来说，其意义是指定本布局相对于父布局的重力方向，由于该布局的已经是根布局，其父布局是整个屏幕，那么该参数设置的是相对于屏幕的位置，可以换不同的参数
top|bottom|left|right
等等参数来试验。

现在增加参数
android:gravity

=

"bottom|right"

完整

XML

如下，看看效果

 
<?
xml

version
=
"1.0"

encoding
=
"utf-8"

?>

<
LinearLayout
xmlns:android
=
"http://schemas.android.com/apk/res/android"

                     
android:layout_height
=
"200dp"

                     

android:layout_width
=
"200dp"

                     

android:background

=

"#AABBCC"

                     

android:orientation="horizontal"

                     

android:layout_gravity=
"center"

                     

android:gravity

=

"bottom|right

"

>

                     

<
TextView
android:text
=
"ONE"

 
                                  

android:background
=
"#aa0000"

 
                                  

android:layout_height
=
"wrap_content"

 
                                  

android:layout_width
=
"wrap_content"

 
                                  

android:layout_margin
=
"1dp"

/>

 
                   

<
TextView
android:text
=
"TWO"

 
                                  

android:background
=
"#aa0000"

 
                                  

android:layout_height
=
"wrap_content"

 
                                  

android:layout_width
=
"wrap_content"

 
                                  

android:layout_margin
=
"1dp"

/>

</

LinearLayout

>

 



通过改变android:gravity

参数的值可以看到实际效果。

参数
android:orientation=

"

horizontal

"

决定了每个子元素各占一列，如果

参数
android:orientation=

"

vertical

"

，

则每个子元素各占一行，也就是从上到下排列了。

对于

LinearLayout

布局的子元素，给每个子元素加上参数

android:layout_weight

看看效果

<?
xml

version
=
"1.0"

encoding
=
"utf-8"

?>

<
LinearLayout
xmlns:android
=
"http://schemas.android.com/apk/res/android"

 
                   

android:layout_height
=
"200dp"

 
                   

android:layout_width
=
"200dp"

 
                   

android:background
=
"#AABBCC"

 
                   

android:layout_gravity
=
"center"

 
                   

android:gravity
=
"bottom|right"

 
                   

android:orientation
=
"horizontal"

>

 
                   

<
TextView
android:text
=
"ONE"

 
                                  

android:background
=
"#aa0000"

 
                                  

android:layout_height
=
"wrap_content"

 
                                  

android:layout_width
=
"wrap_content"

 
                                  

android:layout_margin
=
"1dp"

 
                                  

android:layout_weight
=
"1"

/>

 
                   

<
TextView
android:text
=
"TWO"

 
                                  

android:background
=
"#aa0000"

 
                                  

android:layout_height
=
"wrap_content"

 
                                  

android:layout_width
=
"wrap_content"

 
                                  

android:layout_margin
=
"1dp"

 
                                  

android:layout_weight
=
"2"

/>

</
LinearLayout
>



 
 
 
Text
为ONE
的权重为1
，但明显占的宽度比TWO
的小，百思不得其解，后来得知，如果把TextView

的参数android:layout_width

=

"wrap_content"

全部修改为

android:layout_width

=

"fill_parent"
,

则

ok

，代码如下

<?
xml

version
=
"1.0"

encoding
=
"utf-8"

?>

<
LinearLayout
xmlns:android
=
"http://schemas.android.com/apk/res/android"

                     
android:layout_height
=
"200dp"

                     
android:layout_width
=
"200dp"

                     
android:background
=
"#AABBCC"

                     
android:layout_gravity
=
"center"

                     
android:gravity
=
"bottom|right"

                     
android:orientation
=
"horizontal"

>

                     
<
TextView
android:text
=
"ONE"

                                     android:background
=
"#aa0000"

                                    
android:layout_height
=
"wrap_content"

                                    
android:layout_width
=
"

fill_parent

"

                                    
android:layout_margin
=
"1dp"

                                    
android:layout_weight
=
"1"

/>

                     
<
TextView
android:text
=
"TWO"

                                     android:background
=
"#aa0000"

                                     android:layout_height
=
"wrap_content"

                                     android:layout_width
=
"

fill_parent

"

                                     android:layout_margin
=
"1dp"

                                     android:layout_weight
=
"2"

/>

</
LinearLayout
>