Question

I’m trying to get shake gesture to work. Here is some code

In my implementation file

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

        NSLog(@"Shake gesture detected");

    }
}

- (BOOL)canBecomeFirstResponder
{ 
    return YES; 
}

I read that in order to make shake gesture to work UIView should be the firstResponder. This is why I added that code in implementation

if(self.view.isFirstResponder)
    {
        NSLog(@"first");
    }
    else
    {
        NSLog(@"no");
    }

- (void)viewDidAppear {
    [self becomeFirstResponder];
}

When I run the app the output of NSLog is NO. What I miss ? And how to get shake gesture to work

Answer 1

I guess you’re doing this in your UIViewController? That’s not correct … You have to subclass UIView like this:

ShakeView.h:

//
//  ShakeView.h
//

#import <UIKit/UIKit.h>

@interface ShakeView : UIView {

}

- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event;
- (BOOL)canBecomeFirstResponder;

@end

ShakeView.m:

//
//  ShakeView.m
//

#import "ShakeView.h"

@implementation ShakeView

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
    }
    return self;
}

- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event
{
    if ( event.subtype == UIEventSubtypeMotionShake ) {
    }    
    if ( [super respondsToSelector:@selector(motionEnded:withEvent:)] ) {
        [super motionEnded:motion withEvent:event];
    }
}

- (BOOL)canBecomeFirstResponder
{
    return YES;
}

@end

Then use ShakeView instead of your “normal” UIView and implement this in your UIViewController:

- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event
{
    NSLog(@"Shake happend …");
}

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

- (void)viewWillDisappear:(BOOL)animated
{
    [self.view resignFirstResponder];
    [super viewWillDisappear:animated];
}

That’s it. Hope it helps 🙂