iOS 6 - 状态保存和恢复

Question

我已经实现了用于状态保存的iOS 6 API,它可以工作 - 在我退出应用程序并重新启动几毫秒后,恢复的视图控制器会进入,但随后它被我在启动时显示的主视图控制器所取代.

每次应用程序启动主窗口的根视图时我都会设置,所以这一定是问题所在.

这是我的代码:

- (BOOL)application:(UIApplication *)application willFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    [self commonInitializationLaunching:launchOptions];
    return YES;
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    [self commonInitializationLaunching:launchOptions];
    return YES;
}

- (void)commonInitializationLaunching:(NSDictionary *)launchOptions
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{

        self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
        // Override point for customization after application launch.
        static NSString *const kKeychainItemName = @"OAuthGoogleReader";
        self.viewController = [[ViewController alloc] initWithNibName:@"ViewController" bundle:nil];
        self.navController = [[UINavigationController alloc] initWithRootViewController:self.viewController];

        GTMOAuth2Authentication *auth;
        auth = [GTMOAuth2ViewControllerTouch authForGoogleFromKeychainForName:kKeychainItemName
                                                                     clientID:kClientID
                                                                 clientSecret:kClientSecret];

        self.window.rootViewController = self.navController;

        [self.window makeKeyAndVisible];

        BOOL isSignedIn = [auth canAuthorize];
        if (isSignedIn) {
            NSLog(@"Signed");
        }else{
            NSString *scope = @"https://www.google.com/reader/api/";

            GTMOAuth2ViewControllerTouch *viewController;
            viewController = [[GTMOAuth2ViewControllerTouch alloc] initWithScope:scope
                                                                        clientID:kClientID
                                                                    clientSecret:kClientSecret
                                                                keychainItemName:kKeychainItemName
                                                                        delegate:self
                                                                finishedSelector:@selector(viewController:finishedWithAuth:error:)];
            [self.navController pushViewController:viewController animated:YES];
            //        self.window.rootViewController = viewController;
        }
    });
}

你可以看到 - (void)commonInitializationLaunching:(NSDictionary*)launchOptions我正在设置我的窗口的根视图.我不知道该放什么.也许检查是否有保存状态,然后加载此方法？但是怎么样？

谢谢!

以下是我根据Rob的建议尝试的内容:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    if (!self.isRestored) {
        self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    }
    [self commonInitializationLaunching:launchOptions];
    [self.window makeKeyAndVisible];
    return YES;
}

什么都没有willFinishLaunching......我也从我的commonInitializationLaunching方法中删除了窗口代码.

Answer 1

故事板将为您完成大部分繁重工作,例如恢复窗口.但是,使用代码不会恢复窗口.您需要使用编码器保持根视图控制器.您的代码看起来像这样:

NSString * const AppDelegateRootVCKey = @"AppDelegateRootVCKey";

- (void)application:(UIApplication *)application willEncodeRestorableStateWithCoder:(NSCoder *)coder {
    [coder encodeObject:self.window.rootViewController forKey:AppDelegateRootVCKey];
}

- (void)application:(UIApplication *)application didDecodeRestorableStateWithCoder:(NSCoder *)coder {

    // Grabs the preserved root view controller.
    UIViewController * vc = [coder decodeObjectForKey:AppDelegateRootVCKey];

    if (vc) {
        UIWindow * window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
        window.rootViewController = vc;
        window.restorationIdentifier = NSStringFromClass([window class]);

        // The green color is just to make it obvious if our view didn't load properly.
        // It can be removed when you are finished debugging.
        window.backgroundColor = [UIColor greenColor];

        self.window = window;
    }
}

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

    if (!self.window) {

        UIWindow *window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

        // The blue color is just to make it obvious if our view didn't load properly.
        // It can be removed when you are finished debugging.
        window.backgroundColor = [UIColor blueColor];

        UIViewController *root = // However you create your root.

        window.rootViewController = root;
        window.restorationIdentifier = NSStringFromClass([window class]);

        self.window = window;
    }

    [self commonInitializationLaunching:launchOptions];
    [self.window makeKeyAndVisible];

    return YES;
}

另外需要注意的是确保您的UINavigationControllers和UITabBarControllers具有恢复标识符.

Answer 2

状态恢复通常与故事板集成在一起.如果您正在使用故事板,则不应创建自己的窗口,查看控制器等.您应该让故事板为您执行此操作.发生的事情是故事板正在进行所有状态恢复,然后你正在创建一个新窗口并将其置于所有状态之上.如果是这种情况,您可能会在每次启动时创建两个UI副本.你只是没有注意到它.

如果您在代码中构建整个接口(不是推荐的方法,但它确实有效),那么您需要确定在创建UI之前是否发生了状态恢复.这很简单:

• 在您的commonInitializationLaunching:初始化中,仅初始化非UI元素(不会出现在状态保存中的事物).这是处理UI元素在状态恢复期间可能依赖的事物的地方.您当前的代码中没有任何这些.

• 在application:didDecodeRestorableState:,设置应用程序委托ivar以指示状态已恢复.

• 在application:didFinishLaunchingWithOptions:运行后commonInitializationLaunching:,请检查您的伊娃.如果未恢复状态,请创建UI.

请记住,该commonInitializationLaunching:模式仅用于向后兼容iOS 5.如果您不需要,则只需将非UI willFinish和UI放入didFinish(如果状态未恢复).