以编程方式在两个 UIViewController 之间切换

Question

我有两个 xib 文件，每个文件都有一个覆盖 UIViewController 类的类。我在第一个 xib 文件中有一个按钮，当它被按下时应该带我到新的 UIViewController。我设法以不同的方式实现了这种转变：

UIViewController* secondViewController = [[UIViewController alloc] initWithNibName:@"SecondViewControllerName" bundle:[NSBundle mainBundle]];
        [self.view addSubview:secondViewController.view];

或

UIViewController* secondViewController = [[UIViewController alloc] initWithNibName:@"SecondViewControllerName" bundle:[NSBundle mainBundle]];
        [self.navigationController pushViewController:secondViewController animated:YES];

在第二个 UIViewController xib 文件中，我还有一个按钮可以让我回到第一个 UIViewController。但我不知道如何导航回第一个 UIViewController。

我试过了：

[self.navigationController popViewControllerAnimated:YES];

对于导航到第二个 UIViewController 的第二种方式，但我得到 unrecognized selector sent to instance 错误。

非常感谢任何形式的帮助。

---

[编辑#1：添加源代码]

这是第一个视图控制器.m文件的源代码：

#import "ViewController.h"
#import "SecondViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

- (IBAction)switchToSecondPage:(id)sender
{
    SecondViewController *secondViewController = [[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil];

    [UIView beginAnimations:@"flipping view" context:nil];
    [UIView setAnimationDuration:1];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
    [UIView setAnimationTransition: UIViewAnimationTransitionCurlDown forView:self.view cache:YES];

    [self.view addSubview:secondViewController.view];

    [UIView commitAnimations];  

}

@end

这里是第二个视图控制器.m文件的源代码：

#import "SecondViewController.h"

@interface SecondViewController ()

@end

@implementation SecondViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

- (IBAction)switchToFirstPage:(id)sender
{
    [UIView beginAnimations:@"flipping view" context:nil];
    [UIView setAnimationDuration:1];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseIn];
    [UIView setAnimationTransition: UIViewAnimationTransitionCurlUp forView:self.view.superview cache:YES];

    [self.view removeFromSuperview];

    [UIView commitAnimations];
}

@end

这是我的 AppDelegate.m 文件：

#import "AppDelegate.h"

#import "ViewController.h"

@implementation AppDelegate

@synthesize window = _window;
@synthesize viewController = _viewController;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.
    self.viewController = [[ViewController alloc] initWithNibName:@"ViewController" bundle:nil];
    self.window.rootViewController = self.viewController;
    [self.window makeKeyAndVisible];
    return YES;
}

- (void)applicationWillResignActive:(UIApplication *)application
{
}

- (void)applicationDidEnterBackground:(UIApplication *)application
{
}

- (void)applicationWillEnterForeground:(UIApplication *)application
{
}

- (void)applicationDidBecomeActive:(UIApplication *)application
{
}

- (void)applicationWillTerminate:(UIApplication *)application
{
}

@end

整个项目被制作为单视图应用程序，并针对 XCode 4.3 中的 iOS 5.1。我找到了示例项目，它与我遇到的问题相同。这是该项目的 URL：http://www.devx.com/wireless/Article/42476/0/page/2 它只是为早期的 iO​​S 版本编写的。有没有人能看出我做错了什么，因为我真的没有想法？

PS：无论是否在代码中使用此动画，都会出现同样的问题，所以动画没有问题，我已经检查过了。

---

[编辑#2：添加错误信息]

这是错误描述。在返回行的 main 方法中如下所示：

int main(int argc, char *argv[])
{
    @autoreleasepool {
        return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
    }
}

我收到此错误：

线程 1：EXC_BAD_ACCESS（代码=1，地址=0xc00000008）

---

[编辑#3：解决方案]

我要感谢@btype 下面的解决方案。我发现了为什么编辑#2 中的代码不起作用。问题是这样做：

SecondViewController *secondViewController = [[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil];

IBAction 方法的内部！看起来 ARC 会在到达范围结束时立即擦除我的 UIViewController，这就是为什么我得到有关向已发布实例发送消息的信息的原因。我在 ViewController 类中创建了 SecondViewController 私有字段，之后一切正常。

如果有人认为我的解释是错误的并且知道真正困扰我的地方，请随时回答这个问题并纠正我。

Answer 1

编辑代码：

在 AppDelegate.m 中

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
// Override point for customization after application launch.
ViewController *viewController = [[ViewController alloc] initWithNibName:@"ViewController" bundle:nil];

UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:viewController];
self.window.rootViewController = navController;
[self.window makeKeyAndVisible];
return YES;
}

FirstViewController.m

- (IBAction)switchToSecondPage:(id)sender
{
    [self.navigationController pushViewController:secondViewController animated:YES];
}

SeconViewController.m

- (IBAction)switchToFirstPage:(id)sender
{
    [self.navigationController popToRootViewControllerAnimated:YES];
}

这应该会有所帮助。