有条件地从AppDelegate的情节提要中的不同位置开始

我有一个故事板设置了正常的登录名和主视图控制器，后者是成功登录后用户导航到的视图控制器。我的目标是，如果身份验证成功（存储在钥匙串中），则立即显示主视图控制器；如果身份验证失败，则显示登录视图控制器。基本上，我想在AppDelegate中执行此操作：

// url request & response work fine, assume success is a BOOL here
// that indicates whether login was successful or not

if (success) {
          // 'push' main view controller
} else {
          // 'push' login view controller
}

我知道方法performSegueWithIdentifier：但是该方法是UIViewController的实例方法，因此无法从AppDelegate中调用。如何使用现有的情节提要板来完成此任务？

编辑：

情节提要的初始视图控制器现在是未连接任何东西的导航控制器。我使用了setRootViewController：区别，因为MainIdentifier是UITabBarController。这就是我的代码：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{        
    BOOL isLoggedIn = ...;    // got from server response

    NSString *segueId = isLoggedIn ? @"MainIdentifier" : @"LoginIdentifier";
    UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Storyboard" bundle:nil];
    UIViewController *initViewController = [storyboard instantiateViewControllerWithIdentifier:segueId];

    if (isLoggedIn) {
        [self.window setRootViewController:initViewController];
    } else {
        [(UINavigationController *)self.window.rootViewController pushViewController:initViewController animated:NO];
    }

    return YES;
}

欢迎提出建议/改进！

我假设您的情节提要板被设置为“主情节提要板”（UIMainStoryboardFileInfo.plist中的键）。在这种情况下，UIKit将加载情节提要，并将其初始视图控制器设置为窗口的根视图控制器，然后再发送application:didFinishLaunchingWithOptions:到AppDelegate。

我还假定情节提要中的初始视图控制器是导航控制器，您要将主视图或登录视图控制器推入该导航控制器。

您可以向窗口询问其根视图控制器，并将performSegueWithIdentifier:sender:消息发送给它：

NSString *segueId = success ? @"pushMain" : @"pushLogin";
[self.window.rootViewController performSegueWithIdentifier:segueId sender:self];

我对这里提出的一些解决方案感到惊讶。

情节提要中实际上不需要虚拟导航控制器，无需在viewDidAppear：或任何其他黑客上隐藏视图并触发segues。

如果没有在plist文件中配置情节提要，则必须自己创建窗口和根视图控制器：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{        
    BOOL isLoggedIn = ...;    // from your server response

    NSString *storyboardId = isLoggedIn ? @"MainIdentifier" : @"LoginIdentifier";
    UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Storyboard" bundle:nil];
    UIViewController *initViewController = [storyboard instantiateViewControllerWithIdentifier:storyboardId];

    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    self.window.rootViewController = initViewController;
    [self.window makeKeyAndVisible];

    return YES;
}

如果在应用程序的plist中配置了故事板，则在调用application：didFinishLaunching：时将已经设置了窗口和根视图控制器，并且将在窗口上为您调用makeKeyAndVisible。

在这种情况下，它甚至更简单：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{        
    BOOL isLoggedIn = ...;    // from your server response

    NSString *storyboardId = isLoggedIn ? @"MainIdentifier" : @"LoginIdentifier";
    self.window.rootViewController = [self.window.rootViewController.storyboard instantiateViewControllerWithIdentifier:storyboardId];

    return YES;
}

如果您的情节提要的入口点不是UINavigationController：

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


    //Your View Controller Identifiers defined in Interface Builder
    NSString *firstViewControllerIdentifier  = @"LoginViewController";
    NSString *secondViewControllerIdentifier = @"MainMenuViewController";

    //check if the key exists and its value
    BOOL appHasLaunchedOnce = [[NSUserDefaults standardUserDefaults] boolForKey:@"appHasLaunchedOnce"];

    //if the key doesn't exist or its value is NO
    if (!appHasLaunchedOnce) {
        //set its value to YES
        [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"appHasLaunchedOnce"];
        [[NSUserDefaults standardUserDefaults] synchronize];
    }

    //check which view controller identifier should be used
    NSString *viewControllerIdentifier = appHasLaunchedOnce ? secondViewControllerIdentifier : firstViewControllerIdentifier;

    //IF THE STORYBOARD EXISTS IN YOUR INFO.PLIST FILE AND YOU USE A SINGLE STORYBOARD
    UIStoryboard *storyboard = self.window.rootViewController.storyboard;

    //IF THE STORYBOARD DOESN'T EXIST IN YOUR INFO.PLIST FILE OR IF YOU USE MULTIPLE STORYBOARDS
    //UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"YOUR_STORYBOARD_FILE_NAME" bundle:nil];

    //instantiate the view controller
    UIViewController *presentedViewController = [storyboard instantiateViewControllerWithIdentifier:viewControllerIdentifier];

    //IF YOU DON'T USE A NAVIGATION CONTROLLER:
    [self.window setRootViewController:presentedViewController];

    return YES;
}

如果您的情节提要的入口点是UINavigationController替换项：

//IF YOU DON'T USE A NAVIGATION CONTROLLER:
[self.window setRootViewController:presentedViewController];

与：

//IF YOU USE A NAVIGATION CONTROLLER AS THE ENTRY POINT IN YOUR STORYBOARD:
UINavigationController *navController = (UINavigationController *)self.window.rootViewController;
[navController pushViewController:presentedViewController animated:NO];

在您的AppDelegate的application:didFinishLaunchingWithOptions方法中，在该return YES行之前添加：

UINavigationController *navigationController = (UINavigationController*) self.window.rootViewController;
YourStartingViewController *yourStartingViewController = [[navigationController viewControllers] objectAtIndex:0];
[yourStartingViewController performSegueWithIdentifier:@"YourSegueIdentifier" sender:self];

替换YourStartingViewController为实际的第一个视图控制器类的名称（不想显示的类），并YourSegueIdentifier替换为该启动控制器和您要实际启动的控制器之间的segue的实际名称（segue之后的那个） ）。

if如果您不总是希望发生这种情况，则将其包装成条件代码。

假设您已经在使用Storyboard，则可以使用它来向用户展示自定义控制器MyViewController（稍微讲解一下followben的回答）。

在AppDelegate.m中：

-(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    MyCustomViewController *controller = [self.window.rootViewController.storyboard instantiateViewControllerWithIdentifier:@"MyCustomViewController"];

    // now configure the controller with a model, etc.

    self.window.rootViewController = controller;

    return YES;
}

传递给InstantiateViewControllerWithIdentifier的字符串引用情节提要ID，可以在界面构建器中进行设置：

只需根据需要将其包装在逻辑中即可。

但是，如果您从UINavigationController开始，则此方法将不会为您提供导航控件。

要从通过界面生成器设置的导航控制器的起点“跳起来”，请使用以下方法：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    UINavigationController *navigation = (UINavigationController *) self.window.rootViewController;

    [navigation.visibleViewController performSegueWithIdentifier:@"my-named-segue" sender:nil];

    return YES;
}

为什么没有首先显示登录屏幕，检查用户是否已经登录并立即按下一个屏幕？全部在ViewDidLoad中。

Swift的实现方式相同：

如果UINavigationController用作情节提要中的入口点

let storyboard = UIStoryboard(name: "Main", bundle: nil)

var rootViewController = self.window!.rootViewController as! UINavigationController;

    if(loginCondition == true){

         let profileController = storyboard.instantiateViewControllerWithIdentifier("ProfileController") as? ProfileController  
         rootViewController.pushViewController(profileController!, animated: true) 
    }
    else {

         let loginController =   storyboard.instantiateViewControllerWithIdentifier("LoginController") as? LoginController 
         rootViewController.pushViewController(loginController!, animated: true) 
    }

这是在iOS7上有效的解决方案。为了加快初始加载速度并且不执行任何不必要的加载，我的情节提要文件中有一个完全空的UIViewcontroller，名为“ DUMMY”。然后，我可以使用以下代码：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    UIStoryboard* storyboard = [UIStoryboard storyboardWithName:@"MainStoryboard" bundle:nil];

    NSString* controllerId = @"Publications";
    if (![NSUserDefaults.standardUserDefaults boolForKey:@"hasSeenIntroduction"])
    {
        controllerId = @"Introduction";
    }
    else if (![NSUserDefaults.standardUserDefaults boolForKey:@"hasDonePersonalizationOrLogin"])
    {
        controllerId = @"PersonalizeIntro";
    }

    if ([AppDelegate isLuc])
    {
        controllerId = @"LoginStart";
    }

    if ([AppDelegate isBart] || [AppDelegate isBartiPhone4])
    {
        controllerId = @"Publications";
    }

    UIViewController* controller = [storyboard instantiateViewControllerWithIdentifier:controllerId];
    self.window.rootViewController = controller;

    return YES;
}

我建议创建一个新的MainViewController，它是Navigation Controller的Root View Controller。为此，只需按住控件，然后拖动Navigation Controller和MainViewController之间的连接，然后从提示中选择“ Relationship-Root View Controller”。

在MainViewController中：

- (void)viewDidLoad
{
    [super viewDidLoad];
    if (isLoggedIn) {
        [self performSegueWithIdentifier:@"HomeSegue" sender:nil];
    } else {
        [self performSegueWithIdentifier:@"LoginSegue" sender:nil];
    }
}

记住要在具有Home和Login视图控制器的MainViewController之间创建序列。希望这可以帮助。:)

在尝试了许多不同的方法之后，我能够用以下方法解决此问题：

-(void)viewWillAppear:(BOOL)animated {

    // Check if user is already logged in
    NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
    if ([[prefs objectForKey:@"log"] intValue] == 1) {
        self.view.hidden = YES;
    }
}

-(void)viewDidAppear:(BOOL)animated{
    [super viewDidAppear:animated];

    // Check if user is already logged in
    NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
    if ([[prefs objectForKey:@"log"] intValue] == 1) {
        [self performSegueWithIdentifier:@"homeSeg3" sender:self];
    }
}

-(void)viewDidUnload {
    self.view.hidden = NO;
}