我正在尝试将一个位图绘制到surfaceView中我可以成功绘制但是我需要根据其他一些用户移动在屏幕上移动该位图但是当我设置时

canvas.drawColor(Color.TRANSPARENT);
 canvas.drawBitmap(bitmap, left, top, null);

它在屏幕中多次绘制相同的位图 .

但是当我这样做的时候

canvas.drawColor(Color.GREEN);
 canvas.drawBitmap(bitmap, left, top, null);

它正常工作只绘制一个位图并移动它，但我需要透明背景而不是彩色 .

码

公共类DotsSurfaceView扩展了SurfaceView实现的SurfaceHolder.Callback {private SurfaceHolder holder;私有布尔创建;位图位图;

@Override
public void surfaceCreated(SurfaceHolder holder) {
    // draw();
    created = true;
}

@Override
// This is always called at least once, after surfaceCreated
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
    // draw();
    created = true;
}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {

}

public DotsSurfaceView(Context context) {
    super(context);
    holder = getHolder();         
    holder.addCallback(this);
    holder.setFormat(PixelFormat.TRANSPARENT);
    Drawable drawable = ARTrackingActivity.contexti.getDrawable(R.drawable.ic_tune_black_24px);
    bitmap =Utils.drawableToBitmap(drawable);
}

public void draw(float left, float top) {
    Canvas canvas = null;
    try {
        canvas = holder.lockCanvas();

        synchronized (holder) {
            draw2(canvas, left, top);
        }
    } finally {
        if (canvas != null) {
            holder.unlockCanvasAndPost(canvas);
        }
    }
}


public void draw2(Canvas canvas, float left, float top) {
    if (created) {
        canvas.drawColor(Color.TRANSPARENT);
        canvas.drawBitmap(bitmap, left, top, null);
    }
}

}

android surfaceview surfaceholder