Android透明画布(surfaceview)

Question

我有一个面板,通过relativelayout放置在另一个视图的顶部.

我想给这个面板一个透明的背景,但是在搜索几个小时之后找不到正确的方法.当我将alpha设置回0时,我最终得到黑色背景.

希望有人可以帮助我.

非常感谢!

该面板通过以下代码绘制:

    import android.content.Context;
    import android.graphics.Canvas;
    import android.graphics.Paint;
    import android.util.AttributeSet;
    import android.view.SurfaceHolder;
    import android.view.SurfaceView;

    public class Panel extends SurfaceView implements SurfaceHolder.Callback {

    private ViewThread mThread;

    Paint paint = new Paint();

    public Panel(Context context, AttributeSet attributeSet) {
        super(context, attributeSet);
        getHolder().addCallback(this);
        mThread = new ViewThread(this);
    }

    public void doDraw(Canvas canvas) {
        canvas.drawARGB(50, 120, 120, 120);

        paint.setARGB(255, 255, 0, 0);
        paint.setStrokeWidth(2);

        int CanvasHeight = canvas.getHeight();
        int CanvasWidth  = canvas.getWidth();

        canvas.drawLine(LeftStartX, LeftStartY, StopX, StopY, paint);
    }

    public void updateDrawing(float LB, float RB, float BD, float AH, float AD ){
        Left = LB;
        Right = RB;
        Distance = BD;
        AHeight = AH;
        ADistance = AD;
    }

    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {}


    public void surfaceCreated(SurfaceHolder holder) {
        if (!mThread.isAlive()) {
            mThread = new ViewThread(this);
            mThread.setRunning(true);
            mThread.start();
        }
    }


    public void surfaceDestroyed(SurfaceHolder holder) {
        if (mThread.isAlive()) {
            mThread.setRunning(false);
        }
    }
}

Answer 1

在构造函数中:

setZOrderOnTop(true);

之后holder.addCallback(this):

holder.setFormat(PixelFormat.TRANSPARENT);

在绘图开始时:

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

Answer 2

在使用关键字 SurfaceView 而不是 Canvas 进行搜索后，我发现这是不可能的。更多信息请参阅：如何使surfaceview透明

因为画布的背景是静态的，所以我给了它完全相同的背景。现在看起来是透明的:)

    Bitmap bg = BitmapFactory.decodeResource(getResources(), R.drawable.background_panel_800_480);
    canvas.drawBitmap(bg, 0, 0, null);