Fast app switching, what do I need?

Question

My App works fine without the multitasking support. But when I activate it in the info.plist, then it crashes every time I pushed something on the navigationController and hit the home button, came back to the app and used the navigationController again. The error message doesn't help me either.

What do I need to do for multitasking support in my app, when I only want the app to do nothing in the background and come back were it was.

Sadly instruments doesn't work correct either since Xcode 4.1 -_-".

The error-message in the console is sometimes:

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[CAContextImpl _isCached]: unrecognized selector sent to instance 0x5b783d0'

Sometimes it is an EXC_BAD_... in the view where I create a switch??? But only if I clicked the home button before! If I only push the view and then go back. Click Home-Buttom. Tap App-Symbol. And then try to push the same view again it crashes. But when I push the view, go back and push the view, it works. It only crashes, when I was in the SpringBoard (clicked the home Button).

Edit:

//AppDelegate class

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    

    [window makeKeyAndVisible];
    [self loadHauptmenu];

    return YES;
}

- (void) loadHauptmenu {
    NSLog(@"loading Hauptmenu");
    navigationController = [[UINavigationController alloc] init];

    HauptMenuViewController *hauptMenuController = [[HauptMenuViewController alloc] init];
    [navigationController pushViewController:hauptMenuController animated:NO];
//    [hauptMenuController release]; //tried this as error, but wasn't it

    [window addSubview:navigationController.view];
}



//Main Menu class

- (void) pushNewViewController:(UIViewController*)pushMe {
    NSLog(@"Der aktuelle navigationController ist: %@", self.navigationController);

    [self.navigationController pushViewController:pushMe animated:YES];
}

- (void) pushNewViewWithClassname:(NSString*)classname {
    UIViewController *viewControllerToPush = [[NSClassFromString(classname) alloc] init];
    [self pushNewViewController:viewControllerToPush];
    [viewControllerToPush release];
}


- (IBAction) pushEinstellungen:(id)sender {
    [self pushNewViewWithClassname:@"EinstellungenViewController"];
}


//view class, which gets pushed

- (id) init {
    self = [super init];
    if (self != nil) {
        self.title = @"Einstellungen";
        //self.view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 416)];
        self.view.backgroundColor = MEDILEARN_COLOR;

        self.tableView = [[UITableView alloc] initWithFrame:CGRectMake(0, 0, 320, 416) style:UITableViewStyleGrouped];
        self.tableView.delegate = self;
        self.tableView.dataSource = self;
        self.tableView.allowsSelection = NO;
        self.tableView.backgroundColor = [UIColor clearColor];
        [self.view addSubview:self.tableView];

        self.fragenSwitch = [[UISwitch alloc] initWithFrame:CGRectMake(194, 8, 94, 28)]; //here is an EXC_BAD_...
        [self.fragenSwitch addTarget:self action:@selector(toggleEnabledForFragenSwitch:) forControlEvents:UIControlEventValueChanged];
        [self.fragenSwitch setOn:[[NSUserDefaults standardUserDefaults] boolForKey:@"randFragen"] animated:NO];

        self.antwortenSwitch = [[UISwitch alloc] initWithFrame:CGRectMake(194, 8, 94, 28)];
        [self.antwortenSwitch addTarget:self action:@selector(toggleEnabledForAntwortenSwitch:) forControlEvents:UIControlEventValueChanged];
        [self.antwortenSwitch setOn:[[NSUserDefaults standardUserDefaults] boolForKey:@"randAntworten"] animated:NO];
    }
    return self;
}

Answer 1

From your description, it does not appear that multitasking is the problem. This reads like your app has a bug. You should try to track that down and fix it.

By default, your app does nothing in the background.