Android 线性布局详解

时间:2021-08-28 15:42:50

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)

                              android:layout_height="fill_parent"属性(垂直方向)


如果某个子元素的android:layout_width="wrap_content"

           android:layout_height="wrap_content”

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4个参数

<?xmlversion="1.0"encoding="utf-8"?>

<LinearLayoutxmlns: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"/>

                            <TextViewandroid: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2TextView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:

 

Android 线性布局详解

 

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

 

<?xmlversion="1.0"encoding="utf-8"?>

<LinearLayoutxmlns: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>

 

Android 线性布局详解

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

<?xmlversion="1.0"encoding="utf-8"?>

<LinearLayoutxmlns: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>

Android 线性布局详解

 

 

 

TextONE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" ,ok,代码如下


<?xmlversion="1.0"encoding="utf-8"?>

<LinearLayoutxmlns: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>

 

Android 线性布局详解