How do I detect when someone shakes an iPhone?

Question

I want to react when somebody shakes the iPhone. I don\'t particularly care how they shake it, just that it was waved vigorously about for a split second. Does anyone know h

Answer 1

First off, I know this is an old post, but it is still relevant, and I found that the two highest voted answers did not detect the shake as early as possible. This is how to do it:

1. Link CoreMotion to your project in the target's build phases:

2. In your ViewController:

   - (BOOL)canBecomeFirstResponder {
       return YES;
   }
   
   - (void)motionBegan:(UIEventSubtype)motion withEvent:(UIEvent *)event
   {
       if (motion == UIEventSubtypeMotionShake) {
           // Shake detected.
       }
   }
   

Answer 2

Just use these three methods to do it

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

for details you may check a complete example code over there

Answer 3

A swiftease version based on the very first answer!

override func motionEnded(_ motion: UIEventSubtype, with event: UIEvent?) {
    if ( event?.subtype == .motionShake )
    {
        print("stop shaking me!")
    }
}

Answer 4

To enable this app-wide, I created a category on UIWindow:

@implementation UIWindow (Utils)

- (BOOL)canBecomeFirstResponder
{
    return YES;
}

- (void)motionBegan:(UIEventSubtype)motion withEvent:(UIEvent *)event
{
    if (motion == UIEventSubtypeMotionShake) {
        // Do whatever you want here...
    }
}

@end

Answer 5

Sorry to post this as an answer rather than a comment but as you can see I'm new to Stack Overflow and so I'm not yet reputable enough to post comments!

Anyway I second @cire about making sure to set the first responder status once the view is part of the view hierarchy. So setting first responder status in your view controllers viewDidLoad method won't work for example. And if you're unsure as to whether it is working [view becomeFirstResponder] returns you a boolean that you can test.

Another point: you can use a view controller to capture the shake event if you don't want to create a UIView subclass unnecessarily. I know it's not that much hassle but still the option is there. Just move the code snippets that Kendall put into the UIView subclass into your controller and send the becomeFirstResponder and resignFirstResponder messages to self instead of the UIView subclass.

Answer 6

First, Kendall's July 10th answer is spot-on.

Now ... I wanted to do something similar (in iPhone OS 3.0+), only in my case I wanted it app-wide so I could alert various parts of the app when a shake occurred. Here's what I ended up doing.

First, I subclassed UIWindow. This is easy peasy. Create a new class file with an interface such as MotionWindow : UIWindow (feel free to pick your own, natch). Add a method like so:

- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event {
    if (event.type == UIEventTypeMotion && event.subtype == UIEventSubtypeMotionShake) {
        [[NSNotificationCenter defaultCenter] postNotificationName:@"DeviceShaken" object:self];
    }
}

Change @"DeviceShaken" to the notification name of your choice. Save the file.

Now, if you use a MainWindow.xib (stock Xcode template stuff), go in there and change the class of your Window object from UIWindow to MotionWindow or whatever you called it. Save the xib. If you set up UIWindow programmatically, use your new Window class there instead.

Now your app is using the specialized UIWindow class. Wherever you want to be told about a shake, sign up for them notifications! Like this:

[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(deviceShaken) name:@"DeviceShaken" object:nil];

To remove yourself as an observer:

[[NSNotificationCenter defaultCenter] removeObserver:self];

I put mine in viewWillAppear: and viewWillDisappear: where View Controllers are concerned. Be sure your response to the shake event knows if it is "already in progress" or not. Otherwise, if the device is shaken twice in succession, you'll have a li'l traffic jam. This way you can ignore other notifications until you're truly done responding to the original notification.

Also: You may choose to cue off of motionBegan vs. motionEnded. It's up to you. In my case, the effect always needs to take place after the device is at rest (vs. when it starts shaking), so I use motionEnded. Try both and see which one makes more sense ... or detect/notify for both!

One more (curious?) observation here: Notice there's no sign of first responder management in this code. I've only tried this with Table View Controllers so far and everything seems to work quite nicely together! I can't vouch for other scenarios though.

Kendall, et. al - can anyone speak to why this might be so for UIWindow subclasses? Is it because the window is at the top of the food chain?