Android自定义视图和Alpha动画

Question

I have a custom view on top of other views which I am fading out using a ViewPropertyAnimator like this:

mCustomView.animate().setDuration(sFadeDuration).alpha(0f).setListener(new Animator.AnimatorListener() { ... });

This works but the problem is that I have some views under the mCustomView which will only show after the animation has finished.

What I want is for them to be revealed while the view on top fades away. Strangely, there is one view which behaves as expected, and that is a VideoView (see below for layout structure).

So I see the VideoView fading in under the disappearing view but all the other views just pop up after the animation has finished.

The animated view is a custom view which overrides onDraw like this:

@Override
protected void onDraw(Canvas canvas) {
    TextPaint paint = new TextPaint();
    canvas.drawColor(Color.TRANSPARENT);

    Canvas c = new Canvas(mBitmap);
    c.drawRect(0, 0, mMetrics.widthPixels, mMetrics.heightPixels, paint);

    paint.setColor(mColor);

    canvas.drawBitmap(mBitmap, 0,0, paint);
}

When I do not override onDraw , everything works as expected.

Does anyone know why the other views are not rendered until the animation finishes? Is there a solution to avoid this? Do I have to somehow apply the animation inside of the onDraw method?

Here's the layout structure:

<RelativeLayout>
  <VideoView />
     <RelativeLayout>
            <LinearLayout>
            <TextView />
            <TextView />
            </LinearLayout>

            <LinearLayout>
            <View />
            </LinearLayout>

            <LinearLayout>
            <Button />
            <Button />
            </LinearLayout>

            <Button />

   </RelativeLayout>
   <CustomView />
</RelativeLayout>

Answer 1

VideoView is a subclass of SurfaceView. SurfaceView has special interactions, so that may explain why it is behaving differently. From the SurfaceView docs :

"The view hierarchy will take care of correctly compositing with the Surface any siblings of the SurfaceView that would normally appear on top of it. This can be used to place overlays such as buttons on top of the Surface, though note however that it can have an impact on performance since a full alpha-blended composite will be performed each time the Surface changes."

Try overriding view.isOpaque to be false in your custom view.