Simplest Way to Detect a Pinch

Simplest way to detect a pinch

You want to use the gesturestart, gesturechange, and gestureend events. These get triggered any time 2 or more fingers touch the screen.

Depending on what you need to do with the pinch gesture, your approach will need to be adjusted. The scale multiplier can be examined to determine how dramatic the user's pinch gesture was. See Apple's TouchEvent documentation for details about how the scale property will behave.

node.addEventListener('gestureend', function(e) {
    if (e.scale < 1.0) {
        // User moved fingers closer together
    } else if (e.scale > 1.0) {
        // User moved fingers further apart
    }
}, false);

You could also intercept the gesturechange event to detect a pinch as it happens if you need it to make your app feel more responsive.

Hammer.js: How to detect pinch with any number of / multiple fingers

Well I finally solved it! I don't know if it's a hack but it works!
The solution was quite simple in the end and it was to set the pointers option to 0, yes zero!

var multiPinch = new Hammer.Pinch({event: 'multipinch', pointers: 0, threshold: 0});

Now, this "multipinch" event detects pinches with any number of pointers ranging from 2 to 10.

This was inspired from the docs here: http://hammerjs.github.io/recognizer-pinch/
which say for the pointers option:

| Option   | Default | Description                             |
|:--------:|---------|-----------------------------------------|
| pointers | 1       | Required pointers. 0 for all pointers.  |

So, I tried setting pointers option to 0 for the pinch event and lo, it worked!

How to detect pinch in gesture vs pinch out gesture?

Well, that seems an easy one. The UIPinchGestureRecognizer class has only two properties, scale and velocity. It seems logical that a negative scale would mean an inward pinch, a positive scale an outward pinch.

NB: "negative" might be misleading. "Smaller" is 0.0 < scale < 1.0, "bigger" is scale > 1.0.

jQuery mobile: Pinch/Zoom/Scale Gesture - console.log('something');

The vendor support varies and iOS the only platform whereto use multi-touch Javascript events reliably.

http://developer.apple.com/library/ios/#DOCUMENTATION/AppleApplications/Reference/SafariWebContent/HandlingEvents/HandlingEvents.html#//apple_ref/doc/uid/TP40006511-SW8

From Apple's own documentation.

Is it possible to detect pinch zoom start and end gestures in Eclair (2.1)?

I don't believe so. It would appear that SimpleGestureDectector is only available in API level 8+.

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