Issue making method run at application launch - ios

Question

I'm working on developing an app that uses the camera for a variety of different purposes. Right now, I'm struggling getting a tidbit of code to run when I launch the application:
UIImagePickerController *imageView = [[UIImagePickerController alloc]init];
imageView.delegate = self;
imageView.sourceType = UIImagePickerControllerSourceTypeCamera;
imageView.showsCameraControls = NO;
[self presentViewController:imageView animated:YES completion:NULL];
I need this to execute on the imageView UIView object at launch so when the application is opened, it goes straight to UIImagePickerController. Here is all of my code for the application:
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (void)applicationDidBecomeActive
{
UIImagePickerController *imageView = [[UIImagePickerController alloc]init];
imageView.delegate = self;
imageView.sourceType = UIImagePickerControllerSourceTypeCamera;
imageView.showsCameraControls = NO;
[self presentViewController:imageView animated:YES completion:NULL];
}
#end

Answer 1

If you want to be informed in any controller, you should listen for UIApplicationDidBecomeActiveNotification or similar notifications.
- (void)viewDidLoad
{
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(applicationDidBecomeActive)
name:UIApplicationDidBecomeActiveNotification
object:nil];
}
to unregister, do
[[NSNotificationCenter defaultCenter] removeObserver:self
name:UIApplicationDidBecomeActiveNotification
object:nil];
in dealloc or whenever you don't want to receive the notification anymore.
If you use storyboards, your app delegate should be like this
#implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// Override point for customization after application launch.
return YES;
}
//…
#end
if you don't use storyboards your app delegate might be
#implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
[self.window makeKeyAndVisible];
self.window.rootViewController = [[ViewController alloc] init];
return YES;
}
//…
#end
and your view controller
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(applicationDidBecomeActive)
name:UIApplicationDidBecomeActiveNotification
object:nil];
}
-(void)dealloc
{
[[NSNotificationCenter defaultCenter] removeObserver:self
name:UIApplicationDidBecomeActiveNotification
object:nil];
}
- (void)applicationDidBecomeActive
{
UIImagePickerController *imageViewPickerController = [[UIImagePickerController alloc] init];
imageViewPickerController.sourceType = UIImagePickerControllerSourceTypeCamera;
[self presentViewController:imageViewPickerController
animated:NO
completion:NULL];
}
#end

Answer 2

If you want code to run when you launch the app you should put it in:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
If you want the UIImagePickerController to be the first viewController presented you should set it as the window's rootViewController like this:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// Set up imageView here
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
[self.window makeKeyAndVisible];
self.window.rootViewController = imageView;
return YES;
}
Use presentViewController if/when you want to present it from another viewController that is already onscreen.