iOS在启动时呈现模态视图控制器而不使用flash

Question

我想在首次启动时向用户展示一个教程向导。

有没有办法在应用程序启动时呈现模态UIViewController，而至少在一毫秒内看不到它背后的rootViewController？

现在我正在做这样的事情（为了清楚起见省略了首次启动检查）：

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

    // ...

    UIStoryboard *storyboard = self.window.rootViewController.storyboard;
    TutorialViewController* tutorialViewController = [storyboard instantiateViewControllerWithIdentifier:@"tutorial"];
    tutorialViewController.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
    [self.window makeKeyAndVisible];
    [self.window.rootViewController presentViewController:tutorialViewController animated:NO completion:NULL];
}

没有运气。我试图将[self.window makeKeyAndVisible]; 移到[... presentViewController:tutorialViewController ...] 语句之前，但是模态甚至没有出现。

Answer 1

所有 presentViewController 方法都需要先出现呈现视图控制器。为了隐藏根 VC，必须呈现一个覆盖。启动屏幕可以继续在窗口上显示，直到显示完成，然后淡出覆盖。

    UIView* overlayView = [[[UINib nibWithNibName:@"LaunchScreen" bundle:nil] instantiateWithOwner:nil options:nil] firstObject];
overlayView.frame = self.window.rootViewController.view.bounds;
overlayView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;

UIStoryboard *storyboard = self.window.rootViewController.storyboard;
TutorialViewController* tutorialViewController = [storyboard instantiateViewControllerWithIdentifier:@"tutorial"];
tutorialViewController.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
[self.window makeKeyAndVisible];
[self.window addSubview:overlayView];
[self.window.rootViewController presentViewController:tutorialViewController animated:NO completion:^{
    NSLog(@"displaying");
    [UIView animateWithDuration:0.5 animations:^{
        overlayView.alpha = 0;
    } completion:^(BOOL finished) {
        [overlayView removeFromSuperview];
    }];
}];

Answer 2

布鲁斯在 Swift 3 中的赞成答案：

if let vc = window?.rootViewController?.storyboard?.instantiateViewController(withIdentifier: "LOGIN")
    {
        let launch = UIStoryboard(name: "LaunchScreen", bundle: nil).instantiateInitialViewController()!
        launch.view.frame = vc.view.bounds
        launch.view.autoresizingMask = [UIViewAutoresizing.flexibleWidth, UIViewAutoresizing.flexibleHeight]
        window?.makeKeyAndVisible()
        window?.addSubview(launch.view)

        //Using DispatchQueue to prevent "Unbalanced calls to begin/end appearance transitions"
        DispatchQueue.global().async {
            // Bounce back to the main thread to update the UI
            DispatchQueue.main.async {
                self.window?.rootViewController?.present(vc, animated: false, completion: {

                    UIView.animate(withDuration: 0.5, animations: {
                        launch.view.alpha = 0
                    }, completion: { (_) in
                        launch.view.removeFromSuperview()
                    })
                })
            }
        }
    }

Answer 3

也许你可以使用“childViewController”

UIStoryboard *storyboard = self.window.rootViewController.storyboard;
TutorialViewController* tutorialViewController = [storyboard instantiateViewControllerWithIdentifier:@"tutorial"];

[self.window addSubview: tutorialViewController.view];
[self.window.rootViewController addChildViewController: tutorialViewController];

[self.window makeKeyAndVisible];

当您需要解散您的导师时，您可以从超级视图中删除其视图。您还可以通过设置 alpha 属性在视图上添加一些动画。希望有帮助:)

Answer 4

这个问题在 iOS 10 中仍然存在。我的解决方法是：

1. 在viewWillAppear 中将模态VC 作为childVC 添加到rootVC
2. 在viewDidAppear：
   1. 将 modalVC 作为 rootVC 的子项移除
   2. 以模态方式呈现不带动画的 childVC

代码：

extension UIViewController {

    func embed(childViewController: UIViewController) {
        childViewController.willMove(toParentViewController: self)

        view.addSubview(childViewController.view)
        childViewController.view.frame = view.bounds
        childViewController.view.autoresizingMask = [.flexibleHeight, .flexibleWidth]

        addChildViewController(childViewController)
    }


    func unembed(childViewController: UIViewController) {
        assert(childViewController.parent == self)

        childViewController.willMove(toParentViewController: nil)
        childViewController.view.removeFromSuperview()
        childViewController.removeFromParentViewController()
    }
}


class ViewController: UIViewController {

    let modalViewController = UIViewController()

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        //BUG FIX: We have to embed the VC rather than modally presenting it because:
        // - Modal presentation within viewWillAppear(animated: false) is not allowed
        // - Modal presentation within viewDidAppear(animated: false) is not visually glitchy
        //The VC is presented modally in viewDidAppear:
        if self.shouldPresentModalVC {
            embed(childViewController: modalViewController)
        }
        //...
    }


    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        //BUG FIX: Move the embedded VC to be a modal VC as is expected. See viewWillAppear
        if modalViewController.parent == self {
            unembed(childViewController: modalViewController)
            present(modalViewController, animated: false, completion: nil)
        }

        //....
    }
}

Answer 5

可能是一个糟糕的解决方案，但您可以制作一个包含 2 个容器的 ViewController，其中两个容器都链接到一个 VC。然后你可以控制哪个容器应该在代码中可见，这是一个想法

if (!firstRun) {
    // Show normal page
    normalContainer.hidden = NO;
    firstRunContainer.hidden = YES;
} else if (firstRun) {
    // Show first run page or something similar
    normalContainer.hidden = YES;
    firstRunContainer.hidden = NO;
}

Answer 6

Bruce 的回答为我指明了正确的方向，但是因为我的模式可能会比启动时更频繁地出现（这是一个登录屏幕，所以如果他们注销就需要出现），我不想绑定我的叠加层直接到视图控制器的呈现。

这是我想出的逻辑：

    self.window.rootViewController = _tabBarController;
    [self.window makeKeyAndVisible];

    WSILaunchImageView *launchImage = [WSILaunchImageView new];
    [self.window addSubview:launchImage];

    [UIView animateWithDuration:0.1f
                          delay:0.5f
                        options:0
                     animations:^{
                         launchImage.alpha = 0.0f;
                     } completion:^(BOOL finished) {
                         [launchImage removeFromSuperview];
                     }];

在不同的部分中，我执行了以典型的self.window.rootViewController presentViewController:... 格式呈现我的登录 VC 的逻辑，无论它是应用启动还是其他方式，我都可以使用它。

如果有人关心，我是这样创建叠加视图的：

@implementation WSILaunchImageView

- (instancetype)init
{
    self = [super initWithFrame:[UIScreen mainScreen].bounds];
    if (self) {
        self.image = WSILaunchImage();
    }
    return self;
}

这是启动图像本身的逻辑：

UIImage * WSILaunchImage()
{
    static UIImage *launchImage = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        if (WSIEnvironmentDeviceHas480hScreen()) launchImage = [UIImage imageNamed:@"LaunchImage-700"];
        else if (WSIEnvironmentDeviceHas568hScreen()) launchImage = [UIImage imageNamed:@"LaunchImage-700-568h"];
        else if (WSIEnvironmentDeviceHas667hScreen()) launchImage = [UIImage imageNamed:@"LaunchImage-800-667h"];
        else if (WSIEnvironmentDeviceHas736hScreen()) launchImage = [UIImage imageNamed:@"LaunchImage-800-Portrait-736h"];
    });
    return launchImage;
}

Aaaa 只是为了完成，下面是那些 EnvironmentDevice 方法的样子：

static CGSize const kIPhone4Size = (CGSize){.width = 320.0f, .height = 480.0f};

BOOL WSIEnvironmentDeviceHas480hScreen(void)
{
    static BOOL result = NO;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        result = CGSizeEqualToSize([UIScreen mainScreen].bounds.size, kIPhone4Size);
    });
    return result;
}

Answer 7

let vc = UIViewController()
vc.modalPresentationStyle = .custom
vc.transitioningDelegate = noFlashTransitionDelegate
present(vc, animated: false, completion: nil)

class NoFlashTransitionDelegate: NSObject, UIViewControllerTransitioningDelegate {

    public func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController? {
        if source.view.window == nil,
            let overlayViewController = UIStoryboard(name: "LaunchScreen", bundle: nil).instantiateInitialViewController(),
            let overlay = overlayViewController.view {
                source.view.addSubview(overlay)
                UIView.animate(withDuration: 0, animations: {}) { (finished) in
                    overlay.removeFromSuperview()
            }
        }
        return nil
    }
}

Answer 8

可能会迟到，但在您的 AppDelegate 中您可以这样做：

//Set your rootViewController
self.window.rootViewController=myRootViewController;
//Hide the rootViewController to avoid the flash
self.window.rootViewController.view.hidden=YES;
//Display the window
[self.window makeKeyAndVisible];

if(shouldPresentModal){

    //Present your modal controller
    UIViewController *lc_viewController = [UIViewController new];
    UINavigationController *lc_navigationController = [[UINavigationController alloc] initWithRootViewController:lc_viewController];
    [self.window.rootViewController presentViewController:lc_navigationController animated:NO completion:^{

        //Display the rootViewController to show your modal
        self.window.rootViewController.view.hidden=NO;
    }];
}
else{

    //Otherwise display the rootViewController
    self.window.rootViewController.view.hidden=NO;
}

Answer 9

这就是我使用故事板的方式，它适用于多种模式。 此示例有 3 个。底部、中间和顶部。

请确保在界面生成器中正确设置每个 viewController 的 storyboardID。

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

    UIStoryboard * storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
    BottomViewController *bottomViewController = [storyboard instantiateViewControllerWithIdentifier:@"BottomViewController"];
    UIWindow *window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
    [window setRootViewController:bottomViewController];
    [window makeKeyAndVisible];

    if (!_loggedIn) {
        MiddleViewController *middleViewController = [storyboard instantiateViewControllerWithIdentifier:@"middleViewController"];
        TopViewController *topViewController = [storyboard instantiateViewControllerWithIdentifier:@"topViewController"];

        [bottomViewController presentViewController:middleViewController animated:NO completion:nil];
        [middleViewController presentViewController:topViewController animated:NO completion:nil];

    }
    else {
        // setup as you normally would.
    }

    self.window = window;

    return YES;
}