在左边选User Interface，右边选View，单击Next，在新窗口中的Device Family中选择iPhone，单击Next，打开如下窗口：
输入名称RootView，单击Create，创建了一个.xib文件。用同样的方法再创建两个.xib，名称分别是FirstView和SecondView。
4、修改App Delegate：
4.1 单击AppDelegate.h，在其中添加代码，在@interface之前添加@class RootViewController;在@end之前添加@property (strong, nonatomic) RootViewController *rootViewController;添加之后的代码如下：
view source print ?
#import <UIKit/UIKit.h> @class RootViewController;
@interface AppDelegate : UIResponder <UIApplicationDelegate>
@property (strong, nonatomic) UIWindow *window;
@property (strong, nonatomic) RootViewController *rootViewController;
@end
4.2 单击AppDelegate.m，修改其代码。
在@implementation之前添加#import "RootViewController.h"，在@implementation之后添加@synthesize rootViewController;然后修改didFinishLaunchingWithOptions方法如下：view source print ?
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
// Override point for customization after application launch.
self.rootViewController = [[RootViewController alloc] initWithNibName:@"RootView" bundle:nil];
UIView *rootView = self.rootViewController.view;
CGRect rootViewFrame = rootView.frame;
rootViewFrame.origin.y += [UIApplication sharedApplication].statusBarFrame.size.height;
rootView.frame = rootViewFrame;
[self.window addSubview:rootView];
self.window.backgroundColor = [UIColor whiteColor];
[self.window makeKeyAndVisible];
return YES;
}
① self.rootViewController = [[RootViewController alloc] initWithNibName:@"RootView" bundle:nil];
这行代码用于从RootView.xib文件中初始化rootViewController，注意initWithNibName:@"RootView"中不要后缀名.xib
② rootViewFrame.origin.y += [UIApplication sharedApplication].statusBarFrame.size.height;
使得RootViewController的视图不会被状态栏挡住
5、修改RootViewController.h：
单击RootViewController.h，在其中添加两个属性和一个方法，如下：
view source print ?
#import <UIKit/UIKit.h>
@class FirstViewController;
@class SecondViewController;
@interface RootViewController : UIViewController
@property (strong, nonatomic) FirstViewController *firstViewController;
@property (strong, nonatomic) SecondViewController *secondViewController;
- (IBAction)switchViews:(id)sender;
@end
