GhostView

GhostView可以在不改变View的parent的情况下，在自己的Overlay里绘制另一个View。被绘制的View不会在它的Parent里绘制，因为View的visibility被设为INVISIBLE。GhostView使用被绘制的View的 render node去绘制。当GhostView为VISIBLE时，它所绘制的View为INVISIBLE；当GhostView为INVISIBLE时，它所绘制的View为VISIBLE。

public class GhostView extends View

构造方法：和被绘制的View相互持有，将被绘制的View的transition visibility设为INVISIBLE，触发View的Parent刷新。

绘制方法：使用View的updateDisplayListIfDirty获取RenderNode进行绘制

创建方法：addGhost(View , ViewGroup , Matrix) 与 addGhost(View , ViewGroup)

Example:

MainActivity.java

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    final TextView textView = (TextView) this.findViewById(R.id.textview);
    ColorDrawable colorDrawable = new ColorDrawable(Color.BLUE);
    colorDrawable.setAlpha(100);
    colorDrawable.setBounds(0, 0, 200, 200);
    textView.getOverlay().add(colorDrawable);

    final FrameLayout frameLayout = (FrameLayout) this.findViewById(R.id.frameLayout);
    frameLayout.setRight(frameLayout.getLeft() + 500);
    frameLayout.setBottom(frameLayout.getTop() + 200);
    MainActivity.this.addGhost(textView, frameLayout);

    this.findViewById(R.id.textview2).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            textView.setText("Change To another");
        }
    });
}

private void addGhost(View view, ViewGroup viewGroup) {
    try {
        Class ghostViewClass = Class.forName("android.view.GhostView");
        Method addGhostMethod = ghostViewClass.getMethod("addGhost", View.class,
                ViewGroup.class, Matrix.class);
        View ghostView = (View) addGhostMethod.invoke(null, view, viewGroup, null);
        ghostView.setBackgroundColor(Color.YELLOW);
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (NoSuchMethodException e) {
        e.printStackTrace();
    } catch (InvocationTargetException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    }
}

效果：

device-2017-03-20-164414.png

点击CHANGE按钮，改变Button的Text，可以看到GhostView也随之更新：

将GhostView设为INVISIBLE，原来的View正常绘制：

device-2017-03-20-164430.png