Java 在主屏幕上使用后台服务绘制位图图像

我有一个带有ready按钮的UI，当这个按钮点击一个调用的后台服务时。我需要在主屏幕上设置位图图像，就像屏幕上的划痕一样。有没有办法做到这一点而不显示活动中的布局。或者，即使我们使用布局在屏幕上显示图像，我也需要背景（主页、按钮和当前打开的所有其他内容）处于活动状态。 .

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我已经附上上面的图片作为参考，你可以看到我想做什么。请帮帮我。我们将非常感谢您的关注。

您的回答太晚了，但也许这可以拯救其他人一天……）

Permission:android.Permission.SYSTEM\u ALERT\u窗口

 class ScreenOverlayService extends Service {
HUDView mView;

@Override
public IBinder onBind(Intent intent) {
    return null;
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    Log.i("onStartCommand", "called....");      

    //      return android.app.Service.START_STICKY;    // don't kill service...
    return START_NOT_STICKY;
}

@Override
public void onCreate() {
    super.onCreate();

    mView = new HUDView(this);

    WindowManager.LayoutParams params = new WindowManager.LayoutParams(
            WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY,
            WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH,
            PixelFormat.TRANSLUCENT);

    params.gravity = Gravity.RIGHT | Gravity.TOP;
    params.setTitle("Load Average");
    WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
    wm.addView(mView, params);

}

@Override
public void onDestroy() {
    super.onDestroy();

    if(mView != null){
        ((WindowManager) getSystemService(WINDOW_SERVICE)).removeView(mView);
        mView = null;
    }
}

class HUDView extends ViewGroup {
    private Paint mLoadPaint;
    Context context;

    public HUDView(Context context_)
    {
        super(context_);
        context = context_;

        mLoadPaint = new Paint();
        mLoadPaint.setAntiAlias(true);
        mLoadPaint.setTextSize(10);
        mLoadPaint.setARGB(255, 255, 0, 0);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        //canvas.drawText("Hello World", 5, 15, mLoadPaint);

        // Read the image
        Bitmap markerImage = BitmapFactory.decodeResource(getResources(), R.drawable.pic1);

        //  Draw it, centered around the given coordinates
        canvas.drawBitmap(markerImage,
                screenPoint.x - markerImage.getWidth() / 2,
                screenPoint.y - markerImage.getHeight() / 2, null);

    }

    @Override
    protected void onLayout(boolean arg0, int arg1, int arg2, int arg3, int arg4) {
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        return super.onTouchEvent(event);
    }
}

}