Re: GWT Support for Touch Event

Craig:

Tried your suggestion, apparently drawingPaper.addDomHandler and drawingPaper.addHandler are behaving identically. The first touch (equivalent to mouse button down), the first "touch move" (mouse move) and touch end (mouse button up) are working as expected. The subsequent touches and touch moves are unpredictable. It appears that once a touch event is handled (touch down or touch move or touch end) there appears to be a requirement to do a "cleanup". Though it's not clear what it is supposed to be. Any ideas? Please let me know.

Thank You

-Velu

On Monday, September 9, 2019 at 1:49:47 PM UTC-4, Velusamy Velu wrote:

Craig:

I appreciate your suggestion. Behind the scene I'm handling multiple touches, though only one touch is being considered. The difference between your approach and mine is drawingPaper.addDomHandler and drawingPaper.addHandler. I will give it a try and let you know.

Thank You

--v

On Monday, September 9, 2019 at 4:40:38 AM UTC-4, Craig Mitchell wrote:

I found this as well.  I think browser implementation of these old single touch events isn't great.  I switched to using the multi touch versions.  Something like this:

private HashMap<Integer, Touch> touches;

private void handleScreenTouches(JsArray<Touch> newTouches, boolean touchDown) {

  // Update the touch collection

  for (int i=0; i<newTouches.length(); i++) {

    Touch touch = newTouches.get(i);

    if (touch != null) {

      if (touchDown) {

        touches.put(touch.getIdentifier(), touch);

      }

      else {

        touches.remove(touch.getIdentifier());

      }

    }

  }

  // Look through the remaining touches
  for (Touch touch : touches.values()) {
    ...
  }

}

drawingPaper.addDomHandler(event -> {
    handleScreenTouches(event.getChangedTouches(), true);
}, TouchStartEvent.getType()));


drawingPaper.addDomHandler(event -> {
    handleScreenTouches(event.getChangedTouches(), true);
}, TouchMoveEvent.getType()));


drawingPaper.addDomHandler(event -> {
    handleScreenTouches(event.getChangedTouches(), false);
}, TouchEndEvent.getType()));

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