Update UILabel from applicationDidBecomeActive? - iphone

Question

I want to update UILabel by clicking a reload button. Additionally, I want to update the label in background, because it is fetching the new data via XML from my website. Of course it would be nice to auto-update the label when the application is opened. And there is my problem:
I was able to make it work well when user were clicking the button manually. But I don't understand how to do the same by calling my method via "applicationDidBecomeActive". I tried to do it the same way, but it obviously doesn't work because my label is returned nil.
I suppose there is a problem of my understanding and the solution should be quite easy. Thanks for your input! Note: I am a beginner with Objective-C and have sometimes problems with "easy" things. ;-)
Below is a summary of the important code parts:
AppDelegate
- (void)applicationDidBecomeActive:(UIApplication *)application {
[[MyViewController alloc] reloadButtonAction];
}
MyViewController
#synthesize label
- (void)reloadButtonAction {
[self performSelectorInBackground:#selector(updateData) withObject:nil];
}
- (void)updateData {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
// Parse the XML File and save the data via NSUserDefaults
[[XMLParser alloc] parseXMLFileAtURL];
// Update the labels
[self performSelectorOnMainThread:#selector(updateLabels) withObject:nil waitUntilDone:NO];
[pool release];
}
- (void)updateLabels {
NSUserDefaults *variable = [NSUserDefaults standardUserDefaults];
myLabel.text = [variable stringForKey:#"myLabelText"];
// myLabel is nil when calling all of this via AppDelegate
// so no changes to the myLabel are done in that case
// but: it works perfectly when called via button selector (see below)
NSLog(#"%#",myLabel.text);
}
-(void)viewDidLoad {
// Reload button in the center
UIButton *reloadButton = [UIButton buttonWithType:UIBarButtonSystemItemRefresh];
reloadButton.frame = CGRectMake(145,75,30,30);
[reloadButton setTitle:#"" forState:UIControlStateNormal];
[reloadButton addTarget:self action:#selector(reloadButtonAction) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:reloadButton];
}

Answer 1

First:
[[MyViewController alloc] reloadButtonAction];
Doesn't make sense. You allocate memory, without initializing an object. And then you want to call a method on it. Doesn't work
Use an instance for it:
[myViewControllerInstance reloadButtonAction];
In your app delegate you should have an reference to your rootcontroller instance if that is the object contains the reload method, use that instance.
Note:
Alloc only reserves space in the memory for an object which size the size of MyViewController instance. An init method will fill it.