Android surfaceview animation

Question

I'm trying to achieve animation on a surfaceview. But, my surfaceview's background is transparent, and I can't clear away the pixels of last frame. Can I achieve some animations on transparent surfaceview? Maybe I only use 'Animation' class on a view. Thanks!

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Maybe I didn't describe the question clearly. I want to achieve a animation, but surfaceview can't refresh last graph.It looks like the picature.

The background is transparent. I known draw canvas with color can clean the last drawn graph. But its background is transparent, the method doesn't achieve refresh. Please help me. Thanks!

Answer 1

Watch the following code, it worked for me:

Paint clearPaint = new Paint();

public MySurfaceView(Context context, AttributeSet attrs) {
    super(context, attrs);

    this.setZOrderOnTop(true);
    this.getHolder().setFormat(PixelFormat.TRANSPARENT);
    clearPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
}

public void drawMethod(){
    Canvas canvas = this.getHolder().lockCanvas();

    canvas.drawPaint(clearPaint);

    canvas.drawBitmap(yourBitmap, null, yourBitmapRect, null);

    this.getHolder().unlockCanvasAndPost(canvas);
}

You have have to put your SurfaceView on top in Z order and set PixelFormat to transparent. That will make your SurfaceView transparent (this part you've done, as you wrote). Then you have to fill your surface with a transparent paint before each new drawing. This "special" paint needs to be set like so:

clearPaint.setXfermode(new PorterDuffXfermode(Mode.CLEAR));

Answer 2

you can try to canvas.drawColor(Color.BLACK) at the start of every draw()