Shake to do action

chaseacton · August 2009

I currently have a button that when pressed, updates a label with a random number from 1-100. I need to have the same action done when the device is shook. I'm using the following code and would also like a switch to turn on and off the shake ability.

- (IBAction)oneToHundred {
	int rNumber = rand() % 100;
	result.text	 = [[NSString alloc] initWithFormat:@\"%d\", rNumber];
}

rdominelli · August 2009

chaseacton;111937 said:
I currently have a button that when pressed, updates a label with a random number from 1-100. I need to have the same action done when the device is shook. I'm using the following code and would also like a switch to turn on and off the shake ability.
- (IBAction)oneToHundred {
	int rNumber = rand() % 100;
	result.text	 = [[NSString alloc] initWithFormat:@\"%d\", rNumber];
}

Is your question how to implement shake detection? or How to turn that detection on and off?

Rich

chaseacton · August 2009

Both. First i want to be able to shake the device to do that action.

After i get that working, i would like to have a switch to enable/disable the detection.

rdominelli · August 2009

chaseacton;112080 said:
Both. First i want to be able to shake the device to do that action.

After i get that working, i would like to have a switch to enable/disable the detection.

Do a search on this board for shake. There is a better way to do it in 3.0 but honestly I don't recall it off the top of my head.
The old way of doing it is....

In your view controller .h file add the
UIAccelerometerDelegate to the @interface line. For example my code is based on the utility app project type so my viewcontroller interface line looks like
@interface MainViewController : UIViewController

Then in view did load (Viewcontroller.m) add....

// This view should get accel events
[UIAccelerometer sharedAccelerometer].delegate = self;

Then add the following to your view controller .m file
#define kAccelerationThreshold 2.2

- (void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration
{
if (shakeToReset) // Boolean to control whether or not to care about shakes.
{
if (fabsf(acceleration.x) > kAccelerationThreshold || fabsf(acceleration.y) > kAccelerationThreshold || fabsf(acceleration.z) > kAccelerationThreshold)
[self DO SOMETHING];
}
}

Replace DO SOMETHING with the function you want to invoke. Replace shakeToReset with a boolean value which is set by your switch and your in business.

I found the previous before I saw that 3.0 adds a spiff new way and as usual, because it was working I never went back to fix it. But it works solidly.

Rich

rdominelli · August 2009

If you look down the page on this article it has the 3.0 way of doing it.
How do I detect when someone shakes an iPhone? - Stack Overflow

Its the method which uses motion ended.

Rich

chaseacton · August 2009

You should have used code tags because it took me forever to figure out that your frowny faces were actually:

:(

rdominelli · August 2009

chaseacton;112381 said:
You should have used code tags because it took me forever to figure out that your frowny faces were actually:
:(

Sorry bout that. Is it working?

Rich

chaseacton · August 2009

Well, yes and no. I used this code to get it working, but now i need to know how to add a switch to turn on and off the ability to trigger the action when shook.

- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event {
	[self randomNumber];


    [super motionEnded:motion withEvent:event];

rdominelli · August 2009

chaseacton;112439 said:
Well, yes and no. I used this code to get it working, but now i need to know how to add a switch to turn on and off the ability to trigger the action when shook.
- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event {
	[self randomNumber];


    [super motionEnded:motion withEvent:event];

Try

- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event {
        if ([mySwitch isOn])
{
	[self randomNumber];
}


    [super motionEnded:motion withEvent:event];

It still receives the event but it does not call your function if your switch is set.

Rich

chaseacton · August 2009

Thank you so much!

+Rep!

chaseacton · August 2009

Thanks, this worked great but now my action is a :(id)sender{ action. How can i still use the switch because now it doesnt work and i'm getting awarning saying that it may not respond, which it doesnt.

Thanks,
Chase

rdominelli · August 2009

chaseacton;113267 said:
Thanks, this worked great but now my action is a :(id)sender{ action. How can i still use the switch because now it doesnt work and i'm getting awarning saying that it may not respond, which it doesnt.

Thanks,
Chase

I am not sure I am following your question. Your switch doesn't need an action only your button does. isOn is checking the state of the switch in your button action.

Rich

chaseacton · August 2009

My shake action is this:

#pragma mark Motion Handling
- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event {
	if ([mySwitch isOn])
	{
		[self magic];
	}
	
	
    [super motionEnded:motion withEvent:event];
}

, where if the switch is on, the action will be activated. when the action was:

-(IBAction)magic{

}

It worked fine, now the action is:

-(IBAction)magic:(id)sender{

}

and i get the error "may not respond to -magic" because the method types dont match.

rdominelli · August 2009

chaseacton;113292 said:
My shake action is this:
#pragma mark Motion Handling
- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event {
	if ([mySwitch isOn])
	{
		[self magic];
	}
	
	
    [super motionEnded:motion withEvent:event];
}
, where if the switch is on, the action will be activated. when the action was:
-(IBAction)magic{

}
It worked fine, now the action is:
-(IBAction)magic:(id)sender{

}
and i get the error "may not respond to -magic" because the method types dont match.

If you want to use the magic function as both an event handler and a stand alone function you need to either pass a valid id when you are invoking it as a stand alone function or create a simple no param function which is called by both.

Rich

chaseacton · August 2009

Okay, how would I do that?

rdominelli · August 2009

chaseacton;113296 said:
Okay, how would I do that?

You really need to take a day or two and crank through some books. Begining iPhone development or the iPhone cookbook would speed up your development greatly.

In a nutshell you have 3 functions now.

function 1

-(void)doTheRealWork
{
//Do whatever
}

// This function handles the shake
- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event {
if ([mySwitch isOn])
{
[self doTheRealWork];
}

[super motionEnded:motion withEvent:event];
}

// This function would be connected in IB to the switch. Do you really need to do anything when the switch is thrown?
-(IBAction)handleSwitchChange:(id)sender
{
[self doTheRealWork];
}

If needed you can use that last function to also respond to the button clicks etc.

Rich

chaseacton · August 2009

This won't work because doTheRealWork is a

:(id)sender

function, and the shake can't do [self doTheRealWork]; unless the doTheRealWork doesnt have the

:(id)sender

part, which it needs.

Right now I dont care about the switch, I just want the shake to trigger the action.

fxshot · March 2010

chaseacton;113633 said:
This won't work because doTheRealWork is a
:(id)sender
function, and the shake can't do [self doTheRealWork]; unless the doTheRealWork doesnt have the
:(id)sender
part, which it needs.

you need to just pass nil to the method like this:

[self doTheRealWork:nil];

I do that in several places where I have a button from interface builder that triggers an event like my info screen, and then I also have a button that I created in the code that also needs to trigger the action but doesn't require the (id)sender. Sending :nil along will supply what the method requires and will just run the method. You only need to be sure that you are not using sender in the method because if you are it will == nil.

-Mark

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