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MotionEnded is called multiple times

I have a UIViewController subclass that I am trying to handle the shake event when I view it.

Here are the relevant methods that I have implemented:

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    [self becomeFirstResponder];
}

- (void)viewDidDisappear:(BOOL)animated {
    [self resignFirstResponder];
    [super viewDidDisappear:animated];
}

- (BOOL)canBecomeFirstResponder {
    return YES;
}

- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event {
    if (motion == UIEventTypeMotion && event.type == UIEventSubtypeMotionShake) {
        NSLog(@"%@ motionEnded", [NSDate date]);
    }

    if ([super respondsToSelector:@selector(motionEnded:withEvent:)]) {
        [super motionEnded:motion withEvent:event];
    } 
}

You would expect that when I remove ^ + Cmd + Z in iPhone Simulator it will just log once, but it logs sequentially twice for each event. Below is the result of three shake simulations:

2009-10-09 20: 52: 06.216 TestApp [39802: 20b] 2009-10-09 20:52:06 -0400 motionEnded
2009-10-09 20: 52: 06.218 TestApp [39802: 20b] 2009-10-09 20:52:06 -0400 motionEnded
2009-10-09 20: 52: 07.689 TestApp [39802: 20b] 2009-10-09 20:52:07 -0400 motionEnded
2009-10-09 20: 52: 07.690 TestApp [39802 : 20b] 2009-10-09 20:52:07 -0400 motionEnded
2009-10-09 20: 52: 08.001 TestApp [39802: 20b] 2009-10-09 20:52:08 -0400 motionEnded
2009-10-09 20: 52: 08.002 TestApp [39802: 20b] 2009-10-09 20:52:08 -0400 motionEnded

Has anyone seen this and if so how did you fix it? I am using iPhone SDK 3.1 and Xcode version 3.1.4.

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2 answers


Here's what I found looks like a sim error to me:

  • Issue (double motionEnded notification) happens when target is OS 3.1 and 3.1.0 on sim
  • Problem does NOT happen when target is 3.0 on SIM


The problem NEVER happens on the device itself, no matter the purpose.

so it must be a sim bug. When I have a chance, I will post as a bug for apple w / repro

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Haven't seen this, but you can try it without using the super method. By default the implementation motionEnded

(from UIResponder) should be NOP, so there is no need to call the parent method.



Also have you tried this on the device itself? This could be a simulator problem.

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