进入后台状态时关闭UIAlertViews

时间:2010-06-23 22:18:31

标签: ios ios4 background uialertview uiactionsheet

Apple建议在iOS 4中输入后台状态时解除任何UIAlertViews/UIActionSheets。这是为了避免用户在以后重新启动应用程序时出现任何混淆。我想知道我如何能够一次性优雅地解雇所有UIAlertViews,而不是每次我设置它时都保留对它的引用......

有什么想法吗?

12 个答案:

答案 0 :(得分:26)

我的电话是在UIAlertview中添加一个类别,添加以下功能:

- (void) hide {
  [self dismissWithClickedButtonIndex:0 animated:YES];
}

并向UIApplicationWillResignActiveNotification

致敬
[[NSNotificationCenter defaultCenter] addObserver:alertView selector:@selector(hide) name:@"UIApplicationWillResignActiveNotification" object:nil];

答案 1 :(得分:24)

我被Dad's answer(有趣的用户名:)所吸引,并好奇为什么会被投票。

所以我试了一下。

这是UIAlertView的子类的.m部分。

编辑:(Cédric)我添加了一种方法来捕获对委托方法的调用并删除观察者,以避免多次注册到通知中心。

此github仓库中的所有类别捆绑在一起:https://github.com/sdarlington/WSLViewAutoDismiss



    #import "UIAlertViewAutoDismiss.h"
    #import <objc/runtime.h>

    @interface UIAlertViewAutoDismiss () <UIAlertViewDelegate> {
        id<UIAlertViewDelegate> __unsafe_unretained privateDelegate;
    }
    @end

    @implementation UIAlertViewAutoDismiss

    - (id)initWithTitle:(NSString *)title
                message:(NSString *)message
               delegate:(id)delegate
      cancelButtonTitle:(NSString *)cancelButtonTitle
      otherButtonTitles:(NSString *)otherButtonTitles, ...
    {
        self = [super initWithTitle:title
                            message:message
                           delegate:self
                  cancelButtonTitle:cancelButtonTitle
                  otherButtonTitles:nil, nil];

        if (self) {
            va_list args;
            va_start(args, otherButtonTitles);
            for (NSString *anOtherButtonTitle = otherButtonTitles; anOtherButtonTitle != nil; anOtherButtonTitle = va_arg(args, NSString *)) {
                [self addButtonWithTitle:anOtherButtonTitle];
            }
            privateDelegate = delegate;
        }
        return self;
    }

    - (void)dealloc
    {
        privateDelegate = nil;
        [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationDidEnterBackgroundNotification object:nil];
        [super dealloc];
    }

    - (void)setDelegate:(id)delegate
    {
        privateDelegate = delegate;
    }

    - (id)delegate
    {
        return privateDelegate;
    }

    - (void)show
    {
        [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(applicationDidEnterBackground:)
                                                     name:UIApplicationDidEnterBackgroundNotification
                                                   object:nil];

        [super show];
    }

    - (void)applicationDidEnterBackground:(NSNotification *)notification
    {
        [super dismissWithClickedButtonIndex:[self cancelButtonIndex] animated:NO];
        [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationDidEnterBackgroundNotification object:nil];
    }

    #pragma mark - UIAlertViewDelegate

    // The code below avoids to re-implement all protocol methods to forward to the real delegate.

    - (id)forwardingTargetForSelector:(SEL)aSelector
    {
        struct objc_method_description hasMethod = protocol_getMethodDescription(@protocol(UIAlertViewDelegate), aSelector, NO, YES);
        if (hasMethod.name != NULL) {
            // The method is that of the UIAlertViewDelegate.

            if (aSelector == @selector(alertView:didDismissWithButtonIndex:) ||
                aSelector == @selector(alertView:clickedButtonAtIndex:))
            {
                [[NSNotificationCenter defaultCenter] removeObserver:self
                                                                name:UIApplicationDidEnterBackgroundNotification
                                                              object:nil];
            }
            return privateDelegate;
        }
        else {
            return [super forwardingTargetForSelector:aSelector];
        }
    }

    @end

很好用。 这很棒,因为您可以像以前使用UIAlertView一样开始使用它。

我没有时间彻底测试,但我没有发现任何副作用。

答案 2 :(得分:19)

完全不同的方法是递归搜索。

应用程序委托的递归函数

- (void)checkViews:(NSArray *)subviews {
    Class AVClass = [UIAlertView class];
    Class ASClass = [UIActionSheet class];
    for (UIView * subview in subviews){
        if ([subview isKindOfClass:AVClass]){
            [(UIAlertView *)subview dismissWithClickedButtonIndex:[(UIAlertView *)subview cancelButtonIndex] animated:NO];
        } else if ([subview isKindOfClass:ASClass]){
            [(UIActionSheet *)subview dismissWithClickedButtonIndex:[(UIActionSheet *)subview cancelButtonIndex] animated:NO];
        } else {
            [self checkViews:subview.subviews];
        }
    }
}

从applicationDidEnterBackground程序调用它

[self checkViews:application.windows];

答案 3 :(得分:12)

吧。还没有尝试过这个,但是我想知道创建一个UIAlertView的子类来监听这个Notification并关闭它自己是否有意义......

具有“自动”而不保留/保持特征OP正在请求。确保在关闭时取消注册通知(其他繁荣!)

答案 4 :(得分:12)

正如评论中提到的那样:接受的答案不是iOS 4.0以来最好/最干净的答案!我是这样做的:

UIAlertView* alert = [[UIAlertView alloc] initWithTitle:@"Alert!" message:@"This alert will dismiss when application resigns active!" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
[alert show];
[[NSNotificationCenter defaultCenter] addObserverForName:UIApplicationWillResignActiveNotification object:nil queue:[NSOperationQueue mainQueue] usingBlock:^(NSNotification* notification){
        [alert dismissWithClickedButtonIndex:0 animated:NO];
    }];

答案 5 :(得分:7)

我用以下代码解决了这个问题:

/* taken from the post above (Cédric)*/
- (void)checkViews:(NSArray *)subviews {
    Class AVClass = [UIAlertView class];
    Class ASClass = [UIActionSheet class];
    for (UIView * subview in subviews){
        NSLog(@"Class %@", [subview class]);
        if ([subview isKindOfClass:AVClass]){
            [(UIAlertView *)subview dismissWithClickedButtonIndex:[(UIAlertView *)subview cancelButtonIndex] animated:NO];
        } else if ([subview isKindOfClass:ASClass]){
            [(UIActionSheet *)subview dismissWithClickedButtonIndex:[(UIActionSheet *)subview cancelButtonIndex] animated:NO];
        } else {
            [self checkViews:subview.subviews];
        }
    }
}



/*go to background delegate*/
- (void)applicationDidEnterBackground:(UIApplication *)application
{
    for (UIWindow* window in [UIApplication sharedApplication].windows) {
        NSArray* subviews = window.subviews;
        [self checkViews:subviews];
    }
}

答案 6 :(得分:7)

UIAlertView在iOS 8中被弃用,转而使用UIAlertController。不幸的是,这被证明是一个棘手的问题,因为接受的解决方案不起作用,因为Apple显然不支持子类化UIAlertController:

  

UIAlertController类旨在按原样使用,不支持子类化。此类的视图层次结构是私有的,不得修改。

我的解决方案是简单地遍历视图控制器树并关闭您找到的所有UIAlertControllers。您可以通过创建UIApplication的扩展,然后在AppDelegate ReferenceError: $routeParams is not defined at new <anonymous> (http://localhost/music/angularApp.js:124:17) at e (http://localhost/music/js/angular.min.js:39:394) at Object.instantiate (http://localhost/music/js/angular.min.js:40:9) at http://localhost/music/js/angular.min.js:80:442 at A.link (http://localhost/music/js/angular-route.min.js:7:268) at ea (http://localhost/music/js/angular.min.js:73:293) at D (http://localhost/music/js/angular.min.js:62:190) at g (http://localhost/music/js/angular.min.js:55:105) at http://localhost/music/js/angular.min.js:54:249 at http://localhost/music/js/angular.min.js:56:79 <div ng-view="" class="ng-scope"> 方法中调用它来全局启用它。

试试这个(在Swift中):

applicationDidEnterBackground

然后在你的AppDelegate中:

extension UIApplication
{
    class func dismissOpenAlerts(base: UIViewController? = UIApplication.sharedApplication().keyWindow?.rootViewController)
    {
        //If it's an alert, dismiss it
        if let alertController = base as? UIAlertController
        {
            alertController.dismissViewControllerAnimated(false, completion: nil)
        }

        //Check all children
        if base != nil
        {
            for controller in base!.childViewControllers
            {
                if let alertController = controller as? UIAlertController
                {
                    alertController.dismissViewControllerAnimated(false, completion: nil)
                }
            }
        }

        //Traverse the view controller tree
        if let nav = base as? UINavigationController
        {
           dismissOpenAlerts(nav.visibleViewController)
        }
        else if let tab = base as? UITabBarController, let selected = tab.selectedViewController
        {
           dismissOpenAlerts(selected)
        }
        else if let presented = base?.presentedViewController
        {
           dismissOpenAlerts(presented)
        }
    }
}

答案 7 :(得分:3)

直截了当的方法是保存对UIAlertView的引用,以便您可以将其关闭。当然,正如petert所提到的,你可以使用Notification或在UIApplication上使用委托方法

applicationWillResignActive:

并不总是意味着你要去后台。例如,当用户接到电话或接收短信时,您也会收到该代表呼叫和通知(您同时获得)。因此,如果用户收到短信并按取消以保留在您的应用中,您必须决定会发生什么。您可能希望确保您的UIAlertView仍在那里。

所以当你真正进入后台时,我会解雇UIAlertView并在委托调用中保存状态:

applicationDidEnterBackground:

在developer.apple.com上免费查看会话105 - 在WWDC10的iOS4上采用多任务处理。它在16:00分钟变得有趣

查看此graphic以了解应用程序的不同状态

答案 8 :(得分:1)

我在TODO列表中有这个,但我的第一直觉是在你有UIAlertView之类的视图中听取通知UIApplicationWillResignActiveNotification(参见UIApplication) - 在这里你可以通过编程方式删除警报视图用:

(void)dismissWithClickedButtonIndex:(NSInteger)buttonIndex animated:(BOOL)animated

这种方法的讨论甚至暗示了它在iOS4中的用途!

  

在iPhone OS 4.0中,您可能希望在应用程序移至后台时调用此方法。当应用程序移动到后台时,不会自动关闭警报视图。此行为与以前版本的操作系统不同,后者在应用程序终止时自动取消。取消警报视图使您的应用程序有机会保存更改或中止操作,并在以后终止应用程序时执行任何必要的清理。

答案 9 :(得分:0)

如果您只显示一个或两个特定警报窗口(与大多数应用程序一样),那么您只需为警报创建一个assign ivar:

@property (nonatomic, assign) UIAlertView* alertview;

然后,在app delegate:

[self.viewController.alertview dismissWithClickedButtonIndex:[self.viewController.alertview cancelButtonIndex] animated:NO];

您可以将其放在applicationDidEnterBackground:或您认为合适的任何地方。它在应用程序退出时以编程方式关闭警报。我一直这样做,效果很好。

答案 10 :(得分:0)

在UIAlert View上创建类别

使用http://nshipster.com/method-swizzling/ Swizzle“show”方法

通过将星期引用保留在数组中来跟踪显示的警报视图。

-  如果要删除所有数据,请在已保存的警报视图上关闭并清空数组。

答案 11 :(得分:0)

另一种解决方案,基于plkEL,answer,当应用程序放在后台时,移除观察者。如果用户通过按下按钮来解除警报,则观察者仍将处于活动状态,但只有在将应用程序放入后台(块运行的位置 - 使用&#34; nil alertView&#34; - 并且观察者已删除之前) )。

    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:title
                                                message:message
                                               delegate:alertDelegate
                                      cancelButtonTitle:cancelButtonText
                                      otherButtonTitles:okButtonText, nil];
   [alert show];

   __weak UIAlertView *weakAlert = alert;
   __block __weak id observer = [[NSNotificationCenter defaultCenter] addObserverForName:UIApplicationWillResignActiveNotification object:nil queue:      [NSOperationQueue mainQueue] usingBlock:^(NSNotification* notification){
   [weakAlert dismissWithClickedButtonIndex:[weakAlert cancelButtonIndex] animated:NO];
   [[NSNotificationCenter defaultCenter] removeObserver:observer];
    observer = nil;
   }];