Screen turns black on launch xcode simulator - iphone

Question

I've done some research about my problem without fining a solution. My project compiles with success and launches but but the simulator only shows black. My project was working perfectly before I added googles Interstitials to my app. The following is my code to implement this:
Appdelegate.h
#interface AppDelegate : UIResponder <UIApplicationDelegate,GADInterstitialDelegate> {
UIWindow *window_;
MainViewController *mainController;
GADInterstitial *splashInterstitial_;
}
#property (nonatomic, retain) UIWindow *window;
#property(nonatomic, retain) IBOutlet MainViewController *mainController;
#property(nonatomic, readonly) NSString *interstitialAdUnitID;
- (GADRequest *)createRequest;
Appdelegate.m
#define INTERSTITIAL_AD_UNIT_ID #""
#synthesize mainController = mainViewController_;
#synthesize window = window_;
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
[self.window setRootViewController:mainViewController_];
[self.window makeKeyAndVisible];
splashInterstitial_ = [[GADInterstitial alloc] init];
splashInterstitial_.adUnitID = self.interstitialAdUnitID;
splashInterstitial_.delegate = self;
[splashInterstitial_ loadAndDisplayRequest:[self createRequest]
usingWindow:self.window
initialImage:[UIImage imageNamed:#"InitialImage"]];
}
- (void)dealloc {
splashInterstitial_.delegate = nil;
}
- (NSString *)interstitialAdUnitID {
return INTERSTITIAL_AD_UNIT_ID;
}
#pragma mark GADRequest generation
- (GADRequest *)createRequest {
GADRequest *request = [GADRequest request];
request.testDevices =
[NSArray arrayWithObjects:
nil];
return request;
}
MainViewController.h
#interface MainViewController : UIViewController <GADInterstitialDelegate> {
UIButton *interstitialButton_;
GADInterstitial *interstitial_;
}
#property (nonatomic, retain) GADInterstitial *interstitial;
#property (nonatomic, retain) IBOutlet UIButton *interstitialButton;
- (IBAction)showInterstitial:(id)sender;
MainViewController.m
#synthesize interstitialButton = interstitialButton_;
#synthesize interstitial = interstitial_;
- (void)interstitial:(GADInterstitial *)interstitial
didFailToReceiveAdWithError:(GADRequestError *)error {
// Alert the error.
UIAlertView *alert = [[UIAlertView alloc]
initWithTitle:#"GADRequestError"
message:[error localizedDescription]
delegate:nil cancelButtonTitle:#"Drat"
otherButtonTitles:nil] ;
[alert show];
interstitialButton_.enabled = YES;
}
- (void)interstitialDidReceiveAd:(GADInterstitial *)interstitial {
[interstitial presentFromRootViewController:self];
interstitialButton_.enabled = YES;
}
- (IBAction)showInterstitial:(id)sender {
self.interstitial = [[GADInterstitial alloc] init] ;
self.interstitial.delegate = self;
AppDelegate *appDelegate =
(AppDelegate *)
[UIApplication sharedApplication].delegate;
self.interstitial.adUnitID = appDelegate.interstitialAdUnitID;
[self.interstitial loadRequest: [appDelegate createRequest]];
interstitialButton_.enabled = NO;
}