CODEWITHSUNDEEP
javascriptjqueryjquery-uitouch-event
Davis Dimitriov
Davis Dimitriov

Reputation: 4257

Handling iPad touch events for draggables/droppables (undefined changedTouches)

I am trying to get jQuery drag/drop to work nicely with iPad touch events. I found this code on the internet:

function touchHandler(event)
{
    var touches = event.changedTouches,
        first = touches[0],
        type = "";
    switch (event.type)
    {
        case "touchstart": type = "mousedown"; break;
        case "touchmove": type = "mousemove"; break;
        case "touchend": type = "mouseup"; break;
        default: return;
    }

    //initMouseEvent(type, canBubble, cancelable, view, clickCount, 
    //           screenX, screenY, clientX, clientY, ctrlKey, 
    //           altKey, shiftKey, metaKey, button, relatedTarget);

    var simulatedEvent = document.createEvent("MouseEvent");
    simulatedEvent.initMouseEvent(type, true, true, window, 1,
                              first.screenX, first.screenY,
                              first.clientX, first.clientY, false,
                              false, false, false, 0/*left*/, null);

    first.target.dispatchEvent(simulatedEvent);
    event.preventDefault();
}

It appears to work fine if I attach the touchHandler to the document touchstart/move/end, but then no native zooming/scrolling on the iPad is allowed, so I am trying to just attach this handler to the draggables themselves.

The issue that I am seeing with this is that event.changeTouches is always undefined for some reason, as you can witness in http://jsfiddle.net/myLj2/1/ . I can't come up with a reason why a touch event will always have an undefined changeTouches property and because of it, this code won't work. Any thoughts?

Upvotes: 7

Views: 3091

Answers (1)

Davis Dimitriov
Davis Dimitriov

Reputation: 4257

I figured it out after discovering Does jQuery preserve touch events properties?.

It turns out that the jQuery event doesn't copy over the changeTouches property, so you have to either use jQuery's originalEvent property or skip jQuery all together and bind with a function like addEventListener

Upvotes: 9

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