Android无法在画布上绘制透明矩形

Question

尝试绘制透明背景并在上面画线.然而,它绘制黑色矩形而不是透明.如果我将颜色更改为红色,它可以正常工作.所以我猜这是透明的问题.

       drawPoints[currentpoint*4+0] = 0; 
       drawPoints[currentpoint*4+1] = 10;
       drawPoints[currentpoint*4+2] = 20; 
       drawPoints[currentpoint*4+3] = 40;

        Canvas mCanvas = sfh.lockCanvas(new Rect(10,20,50,100));
        mCanvas.drawColor(Color.TRANSPARENT);           
        mCanvas.drawLines(drawPoints,mPaint);
        sfh.unlockCanvasAndPost(mCanvas);

为什么它会变黑？

Answer 1

如果你想要透明度,你可以尝试:

mPaint.setAlpha(100);

或者0到255之间的某个值.

希望有所帮助.