Question

I am developing an app in which I would like to display a view when a touch event is registered. The problem is the view will not display and my code become unresponsive.

Here is my view:

public class TouchFX extends View {

RectF oval;
float Tx, Ty;
Paint paint;
int longSide, numRun;
float top, left, right, bottom;
boolean removable;

public TouchFX(Context context) {
    super(context);
    // TODO Auto-generated constructor stub
    Tx = TouchService.x;
    Ty = TouchService.y;
    paint = new Paint();
    paint.setColor(Color.WHITE);
    paint.setAntiAlias(true);
    paint.setStrokeJoin(Paint.Join.ROUND);
    numRun = 0;
    removable = false;
}

@Override
protected void onDraw(Canvas canvas) {
    // TODO Auto-generated method stub
    super.onDraw(canvas);

    if (canvas.getWidth() > canvas.getHeight())
        longSide = canvas.getWidth();
    else
        longSide = canvas.getHeight();

    if (numRun == 0) {
        left = Tx - (longSide / 15);
        top = Ty + (longSide / 15);
        right = Tx + (longSide / 15);
        bottom = Ty - (longSide / 15);
    } else if (numRun <= 8) {
        left += 2;
        top += 2;
        right += 2;
        bottom += 2;
    }
        oval = new RectF(left, top, right, bottom);

    if (numRun < 9)
        canvas.drawArc(oval, 0, 360, false, paint);
    else
        removable = true;

    numRun++;

    try {
        Thread.sleep(400);
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        }
    }
}

Here is my onTouch handler:

public boolean onTouch(View v, MotionEvent event) {
    // TODO Auto-generated method stub
    if (v == tv && event.getAction() == MotionEvent.ACTION_DOWN
            && isRunning == true) {
        x = event.getX();
        y = event.getY();

        tfx = new TouchFX(this);

        winmngr.addView(tfx, lpFX);


                    //Do some stuff, make some Toasts


        while(!tfx.removable) {
            //waiting for animation to end
        }

        winmngr.removeView(tfx);
    }
    return false;
}

Now, obviously it’s getting stuck within the while loop, but why isn’t it drawing the arc and updating the boolean?

Answer 1

it is getting stuck because onTouch event operates in UI thread (so as onDraw). So you are blocking your UI thread in while loop and onDraw() doesn’t get processor time.

Consider using callback mechanism, so removeView() routines is triggered by your onDraw method. Also sleep(400) in UI thread is extremely bad idea. You can try to use handler and do post delayed execution:

 public class YouCustomView extends View
 {

     Handler handler = new Handler();

     @Override
     protected onDraw(Canvas canvas){
         //your draw routine here
         .... 

         //wait 400 ms and remove view
         handler.postDelayed(new Runnable()
         {
             @Override
             public void run()
             {
                 //trigger callback to remove view
             }
         }, 400);