如何使用故事板呈现启动/登录视图控制器 [英] How to present a splash/login view controller using storyboards

问题描述

我在没有明确答案的情况下以各种形式看到了这个问题。我要在这里问一下这个问题。我的应用程序需要在启动时工作... inits，一些网络调用，登录等。我不希望我的主视图控制器工作，直到完成。这样做的好方法是什么？

I've seen this question in various forms without a clear answer. I'm going to ask and answer here. My app needs to do work on startup... inits, a few network calls, login, etc. I don't want my main view controller working until that's done. What's a good pattern for doing this?

要求：

• iOS5 +，故事板，ARC。


• 主要的vc视图在启动工作完成之前不会出现。


• 想要选择过渡样式到主vc时启动工作已经完成。


• 想在storyboard中尽可能多地进行布局。


• 代码应该干净地包含在显而易见的地方。

• iOS5+, storyboards, ARC.
• the main vc's view cannot appear until the startup work is done.
• want a choice of transition styles to the main vc when the startup work is done.
• want to do as much layout as possible in storyboard.
• the code should be cleanly contained somewhere obvious.

推荐答案

编辑，2017年7月
自第一次写作以来，我已将我的练习改为将我的启动任务交给他们自己的视图控制器。在那个VC中，我检查启动条件，如果需要，提供忙UI等。根据启动时的状态，我设置窗口的根VC。

EDIT, July 2017 Since the first writing, I've changed my practice to one where I give the start up tasks to their own view controller. In that VC, I check startup conditions, present a "busy" UI if needed, etc. Based on the state at startup, I set the window's root VC.

In除了解决OP问题之外，这种方法还具有更好地控制启动UI和UI转换的额外好处。以下是如何操作：

In addition to solving the OP problem, this approach has the additional benefits of giving better control of the startup UI and UI transitions. Here's how to do it:

在主故事板中，添加一个名为 LaunchViewController 的新VC并将其设为应用程序的初始vc。为您的应用程序的真实初始vc提供一个标识符，如AppUI（标识符位于IB中的标识选项卡上）。

In your main storyboard, add a new VC, called LaunchViewController and make it the app's initial vc. Give your app's "real" initial vc an identifier like "AppUI" (identifiers are on the Identity tab in IB).

识别作为主UI启动的其他vcs流程（例如注册/登录，教程等）并提供这些描述性标识符。 （有些人喜欢将每个流程保留在自己的故事板中。这是一个很好的做法，IMO）。

Identify other vcs that are the starts of main UI flows (e.g. Signup/Login, Tutorial, and so on) and give these descriptive identifiers, too. (Some prefer to keep each flow in it's own storyboard. That's a good practice, IMO).

另一个不错的可选想法：给你app的启动故事板的vc也是一个标识符（比如LaunchVC），这样你就可以抓住它并在启动时使用它的视图。这将为用户在启动期间和执行启动任务时提供无缝体验。

One other nice optional idea: give your app's launch storyboard's vc an identifier, too (like "LaunchVC"), so that you can grab it and use it's view during startup. This will provide a seamless experience for the user during launch and while you do your startup tasks.

这是我的 LaunchViewController 看起来像....

Here's what my LaunchViewController looks like....

@implementation LaunchViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    // optional, but I really like this:
    // cover my view with my launch screen's view for a seamless start
    UIStoryboard *storyboard = [self.class storyboardWithKey:@"UILaunchStoryboardName"];
    UINavigationController *vc = [storyboard instantiateViewControllerWithIdentifier:@"LaunchVC"];
    [self.view addSubview:vc.view];
}

- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];
    [self hideBusyUI];
}

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

    // start your startup logic here:
    // let's say you need to do a network transaction... 
    //
    [someNetworkCallingObject doSomeNetworkCallCompletion:^(id result, NSError *error) {
        if (/* some condition */) [self.class presentUI:@"AppUI"];
        else if (/* some condition */) [self.class presentUI:@"LoginUI"];
        // etc.
    }];
}

#pragma mark - Busy UI

// optional, but maybe you want a spinner or something while getting started
- (void)showBusyUI {
    // in one app, I add a spinner on my launch storyboard vc
    // give it a tag, and give the logo image a tag, too
    // here in animation, I fade out the logo and fade in a spinner
    UIImageView *logo = (UIImageView *)[self.view viewWithTag:32];
    UIActivityIndicatorView *aiv = (UIActivityIndicatorView *)[self.view viewWithTag:33];
    [UIView animateWithDuration:0.5 animations:^{
        logo.alpha = 0.0;
        aiv.alpha = 1.0;
    }];
}

- (void)hideBusyUI {
    // an animation that reverses the showBusyUI
}

#pragma mark - Present UI

+ (void)presentUI:(NSString *)identifier {
    UIStoryboard *storyboard = [self storyboardWithKey:@"UIMainStoryboardFile"];
    UINavigationController *vc = [storyboard instantiateViewControllerWithIdentifier:identifier];

    UIWindow *window = [UIApplication sharedApplication].delegate.window;
    window.rootViewController = vc;

    // another bonus of this approach: any VC transition you like to
    // any of the app's main flows
    [UIView transitionWithView:window
                      duration:0.3
                       options:UIViewAnimationOptionTransitionCrossDissolve
                    animations:nil
                    completion:nil];
}

+ (UIStoryboard *)storyboardWithKey:(NSString *)key {
    NSBundle *bundle = [NSBundle mainBundle];
    NSString *storyboardName = [bundle objectForInfoDictionaryKey:key];
    return [UIStoryboard storyboardWithName:storyboardName bundle:bundle];
}

@end

原始答案下面，虽然我更喜欢我当前的方法

让我们表达应用程序准备好用布尔运行主vc，如：

Let's express the app's readiness to run the main vc with a boolean, something like:

BOOL readyToRun = startupWorkIsDone && userIsLoggedIn;

1. 创建一个AppStartupViewController并将其放在app storyboard中。


2. 不要将任何segue拖到它上面，也不要让它成为盯着vc，只是让它漂浮在某个地方。


3. 在故事板中的vc属性检查器中，将其标识符设置为AppStartupViewController。

在AppStartupViewController.m中，当满足readyToRun条件时，它可以解除自身：

In the AppStartupViewController.m, when the readyToRun conditions have been met, it can dismiss itself:

self.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;   // your choice here from UIModalTransitionStyle
[self dismissViewControllerAnimated:YES completion:nil];

现在，只要应用程序变为活动状态，它就可以检查是否准备好运行，并提供AppStartupViewController这是必要的。
在AppDelegate.h中

Now, whenever the app becomes active, it can check for readiness to run, and present the AppStartupViewController if it's needed. In AppDelegate.h

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

    BOOL readyToRun = startupWorkIsDone && userIsLoggedIn;

    if (!readyToRun) {
        UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"MainStoryboard" bundle:nil];
        AppStartupViewController *startupVC = [storyboard instantiateViewControllerWithIdentifier:@"AppStartupViewController"];

        [self.window.rootViewController presentViewController:startupVC animated:NO completion:nil];
        // animate = NO because we don't want to see the mainVC's view
    }
}

这主要是答案，但有一个障碍。不幸的是，在呈现AppStartupViewController之前，主vc被加载（没关系）并获得viewWillAppear：消息（不行）。这意味着我们必须在MainViewController.m中传播一些额外的启动逻辑，如下所示：

That's mostly the answer, but there is one hitch. Unfortunately the main vc gets loaded (that's okay) and gets a viewWillAppear: message (not okay) before the AppStartupViewController is presented. It means we have to spread a little extra startup logic, like this, in MainViewController.m:

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

    if (readyToRun) {
        // the view will appear stuff i would have done unconditionally before
    }
}

我希望这会有所帮助。

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