RoundImageView.java 文件源码

@Override
protected void onDraw(Canvas canvas) {
    Drawable drawable = getDrawable();
    if (drawable instanceof BitmapDrawable) {
        RectF rectF = new RectF(drawable.getBounds());
        int restoreCount = canvas.saveLayer(rectF, null, Canvas.ALL_SAVE_FLAG);
        getImageMatrix().mapRect(rectF);

        Paint paint = ((BitmapDrawable) drawable).getPaint();
        paint.setAntiAlias(true);
        paint.setColor(0xff000000);

        canvas.drawARGB(0, 0, 0, 0);
        canvas.drawRoundRect(rectF, RADIUS, RADIUS, paint);

        Xfermode restoreMode = paint.getXfermode();
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        super.onDraw(canvas);

        // Restore paint and canvas
        paint.setXfermode(restoreMode);
        canvas.restoreToCount(restoreCount);
    } else {
        super.onDraw(canvas);
    }
}