How to use Shake API in iPhone SDK 3.0?

Question

Apple annonced Shake API in iPhone SDK 3.0. I can not find any information regarding this new feature.

Who knows about how to use it? Any example, link will be good.

Cruickshank

Answer 1

The APIs you are looking for are in UIResponder:

- (void)motionBegan:(UIEventSubtype)motion withEvent:(UIEvent *)event;
- (void)motionCancelled:(UIEventSubtype)motion withEvent:(UIEvent *)event;
- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event;

Generally you just implement this:

- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event {
  if (event.type == UIEventSubtypeMotionShake) {
    //Your code here
  }
}

in your UIViewController subclass (UIViewController is a subclass of UIResponder). Also, you want to handle it in motionEnded:withEvent:, not motionBegan:withEvent:. motionBegan:withEvent: is called when the phone suspects shaking is happening, but the OS can determine the difference between a user purposefully shaking, and incidental shaking (like walking up the stairs). If the OS decides it was not a real shake after motionBegan:withEvent: is called it will call motionCancelled: instead of motionEnded:withEvent:.

Coniology

Am I right if I say that we need to add the code [self becomeFirstResponder]; on the view we require shake gesture to work? – Jac

You would be right in saying that. Also: (BOOL)canBecomeFirstResponder {return YES;} – Joliejoliet

Answer 2

I posted a complete 3.0 example in this thread:

How do I detect when someone shakes an iPhone?

Commodore

Keep reading, my response to that post does use 3.0. I uses the events posted above, only I also explain the bit about needing to set the UIView to be first responder which is crucial to it actually working. – Commodore

Answer 3

Joe Hewitt recently committed some code to Three20 that utilizes the 3.0 shake event. Seems like you just need to implement some simple code within -motionBegan:withEvent: inside of your UIResponder.

- (void)motionBegan:(UIEventSubtype)motion withEvent:(UIEvent *)event {
    if (event.type == UIEventSubtypeMotionShake) {
        ...
    }
}

Tanhya