单击按钮时，在运行时将视图放置在另一个视图下方

Question

我的 RelativeLayout 父视图中有一个 VideoView 和一个 ListView。 默认情况下创建活动时，VideoView 位于 ListView 下方，但我希望在运行时单击按钮时更改此设置并将 ListView 放置在 VideoView 下方...我尝试过此操作，但收到错误消息：“循环依赖项在RelativeLayout中是不允许的”..这是我抛出异常的代码

class Audio_Player:AppCompatActivity{
ListView audiolist;
VideoView video;
Button change;
protected override void OnCreate(Bundle savedInstanceState){
 audiolist=(ListView)FindViewById<ListView>(Resource.Id.myaudiolist;
video=(VideoView)FindViewById<VideoView>(Resource.Id.myvideo);
 change=(Button)FindViewById<Button>(Resource.Id.button1);
 change.Click += layout_change;
   } 
//method to change the layout rule on button click
 private void layout_change(object sender,EventArgs e) {
RelativeLayout.LayoutParams layoutParams=new RelativeLayout.LayoutParams(WindowManagerLayoutParams.MatchParent, WindowManagerLayoutParams.WrapContent);
LayoutParams.AddRule(LayoutRules.Below,video.Id);
audiolist.LayoutParameters=layoutParams; 
   } 
} 

Answer 1

RelativeLayout 中不允许循环依赖

从共享错误中，您无法修改RelativeLayout的内部现有控件。 这意味着您只能从 Root RelativeLayout之外添加 View 。

比如创建another_layout.xml如下，它只包含一个Control。 您可以通过您的需求控制对其进行修改。

<?xml version="1.0" encoding="utf-8" ?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/AnotherRootView"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <ListView
        android:text="AnotherListView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:minWidth="25px"
        android:minHeight="25px"
        android:id="@+id/AnotherListView" />

</LinearLayout>

现在回到 Root RelativeLayout，并在其xml中添加android:id="@+id/RootView" 。

然后我们可以在 Root RelativeLayout 中添加another_layout.xml如下：

private void Change_Click(object sender, System.EventArgs e)
{
   // get root view
   RelativeLayout rootView = (RelativeLayout)FindViewById<RelativeLayout>(Resource.Id.RootView);
   // set layout params
    RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(WindowManagerLayoutParams.MatchParent, WindowManagerLayoutParams.WrapContent);
    layoutParams.AddRule(LayoutRules.Below, video.Id);
    // get another layout
    LayoutInflater inflater = (LayoutInflater)this.GetSystemService(Context.LayoutInflaterService);
    LinearLayout linearLayout = (LinearLayout)inflater.Inflate(Resource.Layout.another_layout, null,true);

    // get and set data for anther list view
    ListView anotherListView = (ListView)linearLayout.FindViewById(Resource.Id.AnotherListView);
     
    // we can remove the previous list view
    rootView.RemoveView(audiolist);
    // add another list view which inside the anther layout
    rootView.AddView(linearLayout, layoutParams);

}