//AppDelegate.h中代码#import <UIKit/UIKit.h>@interface AppDelegate : UIResponder <UIApplicationDelegate>@property (retain, nonatomic) UIWindow *window;@end//AppDelegate.m中代码

//RootViewController.h中代码#import <UIKit/UIKit.h>@interface RootViewController : UIViewController@end//RootViewController.m中代码#import "RootViewController.h"#import "BlueViewController.h"#import "RedViewController.h"@interface RootViewController (){    BlueViewController *_blueview;    RedViewController *_redview;}@end@implementation RootViewController-(void)dealloc{    [_blueview release];    [_redview release];    [super dealloc];}- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil{    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];    if (self) {        // Custom initialization    }    return self;}- (void)change:(UIButton *)button{    if (_blueview.view.superview !=nil) {        [_blueview.view removeFromSuperview];        [self.view addSubview:_redview.view];    }else{        [_redview.view removeFromSuperview];        [self.view addSubview:_blueview.view];    }}- (void)viewDidLoad{    [super viewDidLoad];    //蓝色视图控制器的创建    _blueview = [[BlueViewController alloc] init];    _blueview.view.frame = CGRectMake(0, 0, 320, 440);    //添加到根控制器    [self.view addSubview:_blueview.view];        //红色视图控制器创建    _redview = [[RedViewController alloc] init];    _redview.view.frame = CGRectMake(0, 0, 320, 440);//添加到根控制器    [self.view addSubview:_redview.view];        //在根控制器上创建带触发交换事件的按钮    UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];    button.frame = CGRectMake(100, 440, 120, 40);    [button setTitle:@"交换" forState:UIControlStateNormal];    button.backgroundColor = [UIColor blackColor];    [button addTarget:self action:@selector(change:) forControlEvents:UIControlEventTouchUpInside];    [self.view addSubview:button];    // Do any additional setup after loading the view.}- (void)didReceiveMemoryWarning{    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}/*#pragma mark - Navigation// In a storyboard-based application, you will often want to do a little preparation before navigation- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{    // Get the new view controller using [segue destinationViewController].    // Pass the selected object to the new view controller.}*/@end

//BlueViewController.h中代码#import <UIKit/UIKit.h>@interface BlueViewController : UIViewController@end//BlueViewController.m中代码#import "BlueViewController.h"@interface BlueViewController ()@end@implementation BlueViewController- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil{    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];    if (self) {        // Custom initialization    }    return self;}- (void)viewDidLoad{    [super viewDidLoad];    self.view.backgroundColor = [UIColor blueColor];    // Do any additional setup after loading the view.}- (void)didReceiveMemoryWarning{    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}/*#pragma mark - Navigation// In a storyboard-based application, you will often want to do a little preparation before navigation- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{    // Get the new view controller using [segue destinationViewController].    // Pass the selected object to the new view controller.}*/@end

//RedViewController.h中代码#import <UIKit/UIKit.h>@interface RedViewController : UIViewController@end//RedViewController.m中代码#import "RedViewController.h"@interface RedViewController ()@end@implementation RedViewController- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil{    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];    if (self) {        // Custom initialization    }    return self;}- (void)viewDidLoad{    [super viewDidLoad];    self.view.backgroundColor = [UIColor redColor];    // Do any additional setup after loading the view.}- (void)didReceiveMemoryWarning{    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}/*#pragma mark - Navigation// In a storyboard-based application, you will often want to do a little preparation before navigation- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{    // Get the new view controller using [segue destinationViewController].    // Pass the selected object to the new view controller.}*/@end