带有透明活动的画布上的蒙版位图

Question

我为活动实现了自定义ShowCase

我想在画布上画画： http://i.stack.imgur.com/u23kQ.png

遵循以下代码：

mCanvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);

    // draw solid background
    mCanvas.drawColor(mMaskColour);

    // Prepare eraser Paint if needed
    if (mEraser == null) {
        mEraser = new Paint();
        mEraser.setColor(0xFFFFFFFF);
        mEraser.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
        mEraser.setFlags(Paint.ANTI_ALIAS_FLAG);
    }

    // draw (erase) shape
   // mShape.draw(mCanvas, mEraser, mXPosition, mYPosition, mShapePadding);

    mCanvas.drawBitmap(cBitmap,mXPosition,mYPosition,mEraser);

    // Draw background
    canvas.drawBitmap(mBitmap, 0, 0, null);

但看起来像这样：

http://i.stack.imgur.com/MhcOt.png

Answer 1

我解决了这个问题

 Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN));
        mCanvas.drawBitmap(cBitmap,mXPosition,mYPosition,paint);
       // mShape.draw(canvas, mEraser, mXPosition, mYPosition, mShapePadding);
        // Draw the bitmap on our views  canvas.
        canvas.drawBitmap(mBitmap, 0, 0, null);