触摸时使某个位图区域透明

Question

我的想法是将两个图像重叠在一起，并且在onTouch上，顶部图像应该在触摸的半径上变得透明，从而暴露底部图像。这是我叠加2张图片的方式：        Bitmap bmOverlay = Bitmap.createBitmap(bmp1.getWidth(), bmp1.getHeight(), bmp1.getConfig());        Canvas canvas = new Canvas(bmOverlay);        canvas.drawBitmap(bmp1, new Matrix(), null);        canvas.drawBitmap(bmp2, new Matrix(), null);我已经查看了这篇文章，并在下面使用Paint来使其透明：        mPaint = new Paint();        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));        mPaint.setColor(Color.TRANSPARENT);        mPaint.setAntiAlias(true); public void onDraw(Canvas canvas) {            canvas.drawCircle(40, 40, 30, mPaint); //hardcode to test}问题是，我认为圆圈直接使2个图像在定义的半径上透明，我怎样才能使顶部位图透明？

Answer 1

嘿，你的帖子里面有答案！

基本上尝试类似的东西：

public void onDraw(Canvas canvas) {    

    if (myPaintFlag) {

        canvas.drawBitmap(bmp1, new Matrix(), null);

        canvas.drawBitmap(bmp2, new Matrix(), mPaint);

    }

    else {

        canvas.drawBitmap(bmp1, new Matrix(), mPaint);

        canvas.drawBitmap(bmp2, new Matrix(), null);

    }   

}