自iOS 13起UIAlertController消失了 [英] UIAlertController disappearing since iOS 13

问题描述

我具有以下功能，该功能会弹出UIAlert，允许用户更新其触觉反馈设置:

I have the following function that pops up a UIAlert which allows the user to update their Haptic Feedback setting:

- (void)requestHapticSetting{
    UIWindow *alertWindow = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
    alertWindow.rootViewController = [[UIViewController alloc] init];
    alertWindow.windowLevel = UIWindowLevelAlert + 1;
    [alertWindow makeKeyAndVisible];

    if(isHapticOn){
        hapticMessage = @"Haptic feedback is currently\nturned ON.\nPlease update preference.";
    }
    else {
        hapticMessage = @"Haptic feedback is currently\nturned OFF.\nPlease update preference.";
    }

    UIAlertController* alert = [UIAlertController alertControllerWithTitle:@"Haptic Setting"
                                                                   message:hapticMessage
                                                            preferredStyle:UIAlertControllerStyleAlert];

    UIAlertAction* onAction = [UIAlertAction actionWithTitle:@"TURN ON" style:UIAlertActionStyleDefault
                                                     handler:^(UIAlertAction * action) {
                                                         [self saveHapticSettingOn];
                                                     }];

    UIAlertAction* offAction = [UIAlertAction actionWithTitle:@"TURN OFF" style:UIAlertActionStyleDefault
                                                      handler:^(UIAlertAction * action) {
                                                          [self saveHapticSettingOff];
                                                      }];
    [alert addAction:offAction];
    [alert addAction:onAction];
    [alertWindow.rootViewController presentViewController:alert animated:YES completion:nil];
}

我已经使用了两年了，效果很好.

I have used this for a couple of years and it works great.

但是，由于更新到iOS 13并更新到最新的Xcode，我的警报在关闭前弹出不到一秒钟.

However, since updating to iOS 13 and updating to the latest Xcode, my alert pops up for less than a second before closing.

发生了什么变化，才可能使这种情况发生?预先感谢.

What has changed that could be making this happen? Thanks in advance.

推荐答案

似乎已发生的变化是，在iOS 12及更低版本上，您的应用只需调用 [alertWindow makeKeyAndVisible]，即可对窗口保持强大的引用; ，在iOS 13中不再可用.

What seems to have changed is that on iOS 12 and previous versions your app would hold a strong reference to the window just by calling [alertWindow makeKeyAndVisible];, in iOS 13 it doesn't anymore.

正在发生的事情是，对 alertWindow 的唯一强大引用是在您的 requestHapticSetting 函数中，并且一旦该函数返回，该窗口就会被破坏，从而删除您的从视图中发出警报.

What's happening is that the only strong reference to your alertWindow is in your requestHapticSetting func, and as soon as this func returns, the window is destroyed, thus removing your alert from the view.

仅通过采用iOS 13场景即可解决此问题，但我尚未对此进行测试.我所建议的如果使用场景将无法正常工作，是将警报窗口保存在代码中某个位置的强变量中，然后使用它来呈现警报.我建议在单例或AppDelegate本身中这样做.

This might be fixed just by adopting iOS 13 scenes, but I haven't tested that. What I can suggest, which won't properly work if you are using scenes, is holding your alert window in a strong variable somewhere in your code, and then using it to present the alert. I'd suggest doing so in a singleton or AppDelegate itself.

//AppDelegate.h
...
@property (strong) UIWindow *alertWindow;
....

---

//AppDelegate.m
...
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    ...
    self.alertWindow = [[UIWindow alloc] init];
    self.alertWindow.rootViewController = [[UIViewController alloc] init];
    self.alertWindow.windowLevel = UIWindowLevelAlert + 1;
    ...
}
...

---

//Your class that's presenting the alert
#import "AppDelegate.h"
...
- (void)requestHapticSetting{
    AppDelegate *appDelegate = (AppDelegate *)UIApplication.sharedApplication;
    [appDelegate.alertWindow makeKeyAndVisible];
    if(isHapticOn){
        hapticMessage = @"Haptic feedback is currently\nturned ON.\nPlease update preference.";
    } else {
        hapticMessage = @"Haptic feedback is currently\nturned OFF.\nPlease update preference.";
    }

    UIAlertController* alert = [UIAlertController alertControllerWithTitle:@"Haptic Setting"
                                                               message:hapticMessage
                                                        preferredStyle:UIAlertControllerStyleAlert];

    UIAlertAction* onAction = [UIAlertAction actionWithTitle:@"TURN ON" style:UIAlertActionStyleDefault
                                                 handler:^(UIAlertAction * action) {
                                                      [self saveHapticSettingOn];
                                                      [appDelegate.alertWindow setHidden:YES];
                                                 }];

    UIAlertAction* offAction = [UIAlertAction actionWithTitle:@"TURN OFF" style:UIAlertActionStyleDefault
                                                  handler:^(UIAlertAction * action) {
                                                      [self saveHapticSettingOff];
                                                      [appDelegate.alertWindow setHidden:YES];
                                                  }];
    [alert addAction:offAction];
    [alert addAction:onAction];
    [appDelegate.alertWindow.rootViewController presentViewController:alert animated:YES completion:nil];
}

---

对于Swift代码，请检查此答案.

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