Ios blank screen

So i am doing a simple app.I have to nib files.I change the nib that loads first from viewController to firstController but it only shoes a blank screen. Here is my code:

MyAppDelegate.h

#import <UIKit/UIKit.h>

@class IpadAppViewController,FirstPageViewController;

@interface IpadAppAppDelegate : NSObject <UIApplicationDelegate> {
    UIWindow *window;
    IpadAppViewController *viewController;
    IBOutlet FirstPageViewController *firstController;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet IpadAppViewController *viewController;
@property (nonatomic, retain) IBOutlet FirstPageViewController *firstController;

@end

MyAppDel开发者_如何学Cegate.m

//
//  IpadAppAppDelegate.m
//  IpadApp
//
//  Created by Stefan Andrei on 3/24/11.
//  Copyright 2011 IMC. All rights reserved.
//

#import "IpadAppAppDelegate.h"
#import "IpadAppViewController.h"
#import "FirstPageViewController.h"

@implementation IpadAppAppDelegate

@synthesize window;
@synthesize viewController;
@synthesize firstController;


#pragma mark -
#pragma mark Application lifecycle

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

    // Override point for customization after app launch. 
    [self.window addSubview:firstController.view];
    [self.window makeKeyAndVisible];
    return YES;
}


- (void)applicationWillResignActive:(UIApplication *)application {
    /*
     Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
     Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
     */
}


- (void)applicationDidBecomeActive:(UIApplication *)application {
    /*
     Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
     */
}


- (void)applicationWillTerminate:(UIApplication *)application {
    /*
     Called when the application is about to terminate.
     See also applicationDidEnterBackground:.
     */
}


#pragma mark -
#pragma mark Memory management

- (void)applicationDidReceiveMemoryWarning:(UIApplication *)application {
    /*
     Free up as much memory as possible by purging cached data objects that can be recreated (or reloaded from disk) later.
     */
}


- (void)dealloc {
    [viewController release];
    [window release];
    [super dealloc];
}


@end

Before doing [self.window addSubview:firstController.view], you should do

self.firstController = [[[FirstPageViewController alloc] initWithNibName:nil bundle:nil] autorelease];

If you've created FirstPageViewController together with the .xib, then that should be enough, otherwise you may need to pass the nib's name (without the .xib part) in initWithNibName:

Edit: added autorelease - the firstController property is retaining already.