Closing tab bar controllers - iphone

Question

I'm pretty new to iphone programming. I have come up with a problem when using a tab bar controller that I cannot solve. I have an app with 2 tabs each tab uses separate class files and nib files. I use a shake gesture to tell the app to do something but when I changed from tab two back to tab one shake the phone it does the action of the second view not the current view, the current view remains unchanged after the shake.
Am I missing something here? Do I need to release something?
Thanks in advance for any help you can offer.
FirstViewController.m:
#import "FirstViewController.h"
#import <AudioToolbox/AudioToolbox.h>
#implementation FirstViewController
#synthesize label;
- (void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration{
if (fabsf(acceleration.x) > 2.0
|| fabsf(acceleration.y) > 2.0
|| fabsf(acceleration.z) > 2.0) {
label.text = #"Shake";
}
- (void)viewDidLoad {
UIAccelerometer *accelerometer = [UIAccelerometer sharedAccelerometer];
accelerometer.delegate = self;
accelerometer.updateInterval = 1.0f/60.0f;
[super viewDidLoad];
}
- (void)didReceiveMemoryWarning {
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
}
- (void)viewDidUnload {
}
- (void)dealloc {
[super dealloc];
}
#end
SecondViewController.m
#import "SecondViewController.h"
#import <AudioToolbox/AudioToolbox.h>
#implementation SecondViewController
#synthesize label2;
- (void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration{
if (fabsf(acceleration.x) > 2.0
|| fabsf(acceleration.y) > 2.0
|| fabsf(acceleration.z) > 2.0) {
label2.text = #"Shake View 2";
}
- (void)viewDidLoad {
UIAccelerometer *accelerometer = [UIAccelerometer sharedAccelerometer];
accelerometer.delegate = self;
accelerometer.updateInterval = 1.0f/60.0f;
[super viewDidLoad];
}
- (void)didReceiveMemoryWarning {
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
}
- (void)viewDidUnload {
}
- (void)dealloc {
[super dealloc];
}
#end

Answer 1

The accelerometer delegate doesn't change when you switch the tabs in that implementation, because viewDidLoad is only called when the view is loaded into memory and not when displayed.
You could try setting it in the - viewDidAppear:animated method. If that also fails, have a look at the UITabBarControllerDelegate protocol and – tabBarController:didSelectViewController: method. First you need to create and assign the tab bar controller delegate, then implement the method. It could look something like this:
- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController
{
if([viewController respondsToSelector:#sel(wasSelectedFromTabBar)]){
[viewController wasSelectedFromTabBar]
}
}
Then, in your view controllers, assign the accelerometer delegate in the wasSelectedFromTabBar method. Hope it works!

Answer 2

Your view controllers probably aren't set as the first responder. So when you're looking at the view controller on Tab 1, the view controller on Tab 2 is receiving the motion event. I'm making a lot of assumptions here, mind you.
Add this code to both of your view controllers, and as you switch to each of them they will take over as the first responder.
-(BOOL)canBecomeFirstResponder {
return YES;
}
-(void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
[self becomeFirstResponder];
}
- (void)viewWillDisappear:(BOOL)animated {
[self resignFirstResponder];
[super viewWillDisappear:animated];
}