trying to create a Universal app for iOS Devices

I have my iPhone app ready and now i've to make it a Universal app.

I'm doing this..

self.window = [[UIWindow alloc] init];
self.appFrame = [[UIScreen mainScreen] bounds];
self.window.frame = self.appFrame;
UINavigationController *aNav = [[UINavigationController alloc] initWithR开发者_JAVA百科ootViewController:self.myViewController];
aNav.view.frame = self.appFrame; 
self.nav = aNav;
[self.window addSubview:nav.view];
[self.window makeKeyAndVisible];

I don't have MainWindow.xib in my project. I'm creating it programmatically.

So if i use this code to give the frame to the window

self.appFrame = [[UIScreen mainScreen] bounds];
self.window.frame = self.appFrame;

Then it iPad should have (0,0,768,1024) and iPhone should have (0,0,320,480)

But, if I run my code on iPad simulator it takes self.appFrame as (0,0,320,480)

Can you guys explain me what's the problem??

and

How can i create a Universal app without using MainWindow.xib??

Open the Build Settings tab of your target in Xcode and set the Targeted Device Family key to iPhone/iPad. Then your app compiles as native iPad and iPhone application and [[UIScreen mainScreen] bounds] should return the correct results. Btw, you should use [[UIScreen mainScreen] applicationFrame] instead of bounds for the window frame!