jQuery Drag and Drop on touch devices (iPad, Android)

Question

We have a card game website that makes extensive use of jQuery Draggable & Droppable and which has worked nearly flawlessly (when using a mouse) for almost a year.

We would REALLY like to have the site work on touch screen devices, but we cannot seem to get jQuery's drag and especially drop functionality to work reliably.

Dragging works "ok" unless the div being dragged is inside another dom element with any kind of offset, margin, padding, etc. If it is, the dragged element is also offset from the user's finger by a similar amount. May not sound like a big deal, but it makes the interface unusuable.

Dropping just doesn't seem to work.

We've researched various options presented here on SO (will try to update this post with links to some of them if I can), but none work for us.

We've also researched jQuery Mobile but this is still in alpha and even so seems to be more of a framework for making a site emulate the UI of a phone vs what we're looking for.

Most of the SO and Google posts on this topic seem to trail off in late 2010 which makes me think there is an obvious answer that maybe we're just missing.

BTW, the functionality we're looking for is clearly technically possible because the YUI libraries for drag and drop work as expected. Unfortunatly, we can't justtify refactoring the site to switch from jQuery to YUI.

Anyone out there have any ideas? We would settle for a answer that supports only iPad, but it really needs to not require we refactor the existing site.

Thanks!

Answer 1

Paste this at the beginning of your .js file:

(function ($) {
    // Detect touch support
    $.support.touch = 'ontouchend' in document;
    // Ignore browsers without touch support
    if (!$.support.touch) {
    return;
    }
    var mouseProto = $.ui.mouse.prototype,
        _mouseInit = mouseProto._mouseInit,
        touchHandled;

    function simulateMouseEvent (event, simulatedType) { //use this function to simulate mouse event
    // Ignore multi-touch events
        if (event.originalEvent.touches.length > 1) {
        return;
        }
    event.preventDefault(); //use this to prevent scrolling during ui use

    var touch = event.originalEvent.changedTouches[0],
        simulatedEvent = document.createEvent('MouseEvents');
    // Initialize the simulated mouse event using the touch event's coordinates
    simulatedEvent.initMouseEvent(
        simulatedType,    // type
        true,             // bubbles                    
        true,             // cancelable                 
        window,           // view                       
        1,                // detail                     
        touch.screenX,    // screenX                    
        touch.screenY,    // screenY                    
        touch.clientX,    // clientX                    
        touch.clientY,    // clientY                    
        false,            // ctrlKey                    
        false,            // altKey                     
        false,            // shiftKey                   
        false,            // metaKey                    
        0,                // button                     
        null              // relatedTarget              
        );

    // Dispatch the simulated event to the target element
    event.target.dispatchEvent(simulatedEvent);
    }
    mouseProto._touchStart = function (event) {
    var self = this;
    // Ignore the event if another widget is already being handled
    if (touchHandled || !self._mouseCapture(event.originalEvent.changedTouches[0])) {
        return;
        }
    // Set the flag to prevent other widgets from inheriting the touch event
    touchHandled = true;
    // Track movement to determine if interaction was a click
    self._touchMoved = false;
    // Simulate the mouseover event
    simulateMouseEvent(event, 'mouseover');
    // Simulate the mousemove event
    simulateMouseEvent(event, 'mousemove');
    // Simulate the mousedown event
    simulateMouseEvent(event, 'mousedown');
    };

    mouseProto._touchMove = function (event) {
    // Ignore event if not handled
    if (!touchHandled) {
        return;
        }
    // Interaction was not a click
    this._touchMoved = true;
    // Simulate the mousemove event
    simulateMouseEvent(event, 'mousemove');
    };
    mouseProto._touchEnd = function (event) {
    // Ignore event if not handled
    if (!touchHandled) {
        return;
    }
    // Simulate the mouseup event
    simulateMouseEvent(event, 'mouseup');
    // Simulate the mouseout event
    simulateMouseEvent(event, 'mouseout');
    // If the touch interaction did not move, it should trigger a click
    if (!this._touchMoved) {
      // Simulate the click event
      simulateMouseEvent(event, 'click');
    }
    // Unset the flag to allow other widgets to inherit the touch event
    touchHandled = false;
    };
    mouseProto._mouseInit = function () {
    var self = this;
    // Delegate the touch handlers to the widget's element
    self.element
        .on('touchstart', $.proxy(self, '_touchStart'))
        .on('touchmove', $.proxy(self, '_touchMove'))
        .on('touchend', $.proxy(self, '_touchEnd'));

    // Call the original $.ui.mouse init method
    _mouseInit.call(self);
    };
})(jQuery);

Call me in the morning ;) (that's really arrogant, I didn't write this solution although I wish that I had, I'd reference it if I remember where I found it, if anyone know where this code came from please comment and credit that person)

UPDATE: Here you go: This is where I found this