RelativeLayout系列：动态修改内部View的位置

Posted 2021-08-02 zhangjin1120

• 上效果图

“花花”显示在左侧	“花花”显示在右侧

• RelativeLayout内部没有setAbove，setBelow这样的设置，那么，如果想修改子view的位置，该怎么用代码控制？
  RelativeLayout使用LayoutParams来控制位置的， RelativeLayout.LayoutParams中有个addRule()。效果图代码如下：

public class MainActivity extends AppCompatActivity {
   TextView tv;
   Button btn1, btn2;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);
       btn1 = findViewById(R.id.btn1);
       btn2 = findViewById(R.id.btn2);
       tv = findViewById(R.id.tv);


   }

   boolean b = false;
   public void change(View view) {
       if (b) {
           btn1.setVisibility(View.GONE);
           RelativeLayout.LayoutParams lp = (RelativeLayout.LayoutParams) tv.getLayoutParams();
           lp.addRule(RelativeLayout.ABOVE, R.id.btn2);
           lp.addRule(RelativeLayout.ALIGN_PARENT_RIGHT,RelativeLayout.TRUE);
           tv.setLayoutParams(lp);

           b = false;
       } else {
           btn1.setVisibility(View.VISIBLE);
           RelativeLayout.LayoutParams lp = (RelativeLayout.LayoutParams) tv.getLayoutParams();
           lp.addRule(RelativeLayout.ABOVE, R.id.btn1);
           lp.addRule(RelativeLayout.ALIGN_PARENT_RIGHT,0);
           tv.setLayoutParams(lp);

           b = true;
       }
   }
}

布局代码：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="花花"
        android:layout_above="@id/btn2"
        android:layout_alignParentRight="true"
      />

    <Button
        android:id="@+id/btn1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:visibility="gone"
        android:text="可隐藏" />

    <Button
        android:id="@+id/btn2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_centerVertical="true"
        android:text="固定显示" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="change"
        android:text="test"
        />

</RelativeLayout>