未调用 UIApplication WillEnterForegroundNotification

Posted 2023-02-24

【中文标题】未调用 UIApplication WillEnterForegroundNotification

【英文标题】：UIApplicationWillEnterForegroundNotification not called

【发布时间】：2013-08-12 05:28:57

【问题描述】：

您好，我是 Iphone 开发的新手。我有一个问题：

我在我的 Appdeligate 类中使用 UIApplicationDeligate，在这个类中我使用两种方法

applicationDidEnterBackground 和 applicationdisEnterForeGround。然后这些方法可以正常工作，当我的应用程序进入后台或进入前台时，流程会进入这些方法。

但在另一个 UiViewController 类中，我为 UIApplicationdidEnterForegroundNotification 和 UiApplicationdidEnterBackgroundNotification 附加了侦听器。

现在当我的应用程序进入后台时，流程进入后台方法，但是当我的应用程序进入前台时，应用程序流程永远不会进入前台方法。

我在 AppDelegate 类中使用的代码：

- (void)applicationDidEnterBackground:(UIApplication *)application


 NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:timertimetobefired forKey:@"TimerTimeToFired"];
[defaults setValue:timerrecipename forKey:@"TimerRecipeName"];
[defaults setObject:storingbuttonstate forKey:@"TimerButtonState"];





- (void)applicationWillEnterForeground:(UIApplication *)application


    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    timertimetobefired = [defaults objectForKey:@"TimerTimeToFired"];
    timerrecipename = [defaults objectForKey:@"TimerRecipeName"];
    storingbuttonstate = [defaults objectForKey:@"TimerButtonState"];

以及我在 UiViewController 类中使用的代码：

  [[NSNotificationCenter defaultCenter]
 addObserver:self
 selector:@selector(goBackground)
 name:UIApplicationDidEnterBackgroundNotification
 object:nil];


 [[NSNotificationCenter defaultCenter]
  addObserver:@"forground"
  selector:@selector(doMyLayoutStuff:)
  name: UIApplicationWillEnterForegroundNotification
  object:nil];



- (void) goBackground

if(timer != nil && [timer isValid])

 [timer invalidate], timer = nil;

谁能告诉我这段代码有什么问题。提前致谢。

doMylayoutStuff 中的代码：

- (void)doMyLayoutStuff:(id)sender


fortimer=0;
appdelegate.imgRecipePhoto=nil;
recipeMakingTime=0;
arrForStepsReminder=[[NSMutableArray alloc]init];
[arrForStepsReminder removeAllObjects];
arrForSteps5=[[NSMutableArray alloc]init];
[arrForSteps5 removeAllObjects];
arrForButtonSelection=[[NSMutableArray alloc]init];
[arrForButtonSelection removeAllObjects];

[arrForSteps5 addObjectsFromArray:appdelegate.arrStepsandTime];

arrayforshowingdata = [[NSMutableArray alloc]initWithCapacity:arrForSteps5.count];

for (int i=0; i<[arrForSteps5 count]; i++)

    //nitin tyagi. 6/08/2013.

    //        NSString *str12=[[arrForSteps5 objectAtIndex:i]objectForKey:@"RecipestepTime"];
    //        if (str12.length==0)
    //        
    //            [arrForSteps5 removeObjectAtIndex:i];
    //        
    //        else
    //        
    //        

    NSString *timer1 = [[arrForSteps5 objectAtIndex:i]objectForKey:@"RecipeTimer1"];
    NSString *timer2 = [[arrForSteps5 objectAtIndex:i]objectForKey:@"RecipeTimer2"];
    NSString *timer3 = [[arrForSteps5 objectAtIndex:i]objectForKey:@"RecipeTimer3"];
    NSString *timer4 = [[arrForSteps5 objectAtIndex:i]objectForKey:@"RecipeTimer4"];

    timer1 = [timer1 stringByReplacingOccurrencesOfString:@" " withString:@""];
    timer2 = [timer2 stringByReplacingOccurrencesOfString:@" " withString:@""];
    timer3 = [timer3 stringByReplacingOccurrencesOfString:@" " withString:@""];
    timer4 = [timer4 stringByReplacingOccurrencesOfString:@" " withString:@""];

    NSMutableArray *finaltimerarray = [[NSMutableArray alloc]init];


    int totalminute = 0;
    int hours = 0;

    if(([timer1 hasSuffix:@"mins"] || [timer1 hasSuffix:@"minute"] || [timer1 hasSuffix:@"min"]) || ([timer1 isEqualToString:@"0"]))
    
        if(![timer1 isEqualToString:@"0"])
            NSRange range = [timer1 rangeOfString:@"min"];
            NSString *minutes = [timer1 substringToIndex:range.location];
            totalminute = totalminute + [minutes intValue];

            NSNumber* xWrapped = [NSNumber numberWithInt:[minutes intValue]];
            [finaltimerarray addObject:xWrapped];
        
        else
        
            [finaltimerarray addObject:[NSNumber numberWithInt:0]];
        

        // NSLog(@"totalminute minute is = %@",totalminute);
    
    else if(([timer1 hasSuffix:@"hours"] || [timer1 hasSuffix:@"hrs"] || [timer1 hasSuffix:@"hour"] || [timer1 hasSuffix:@"hr"]) )
    
        if(![timer1 isEqualToString:@"0"])
            NSRange range = [timer1 rangeOfString:@"h"];
            NSString *hours = [timer1 substringToIndex:range.location];

            int minute = [hours intValue] * 60;
            totalminute = totalminute + minute;

            NSNumber* xWrapped = [NSNumber numberWithInt:minute];
            [finaltimerarray addObject:xWrapped];
        
        else
        
            [finaltimerarray addObject:[NSNumber numberWithInt:0]];
        

        //  NSLog(@"timer1 minute is = %@",minutes);
    
    if(([timer2 hasSuffix:@"mins"] || [timer2 hasSuffix:@"minute"] || [timer2 hasSuffix:@"min"]) || ([timer2 isEqualToString:@"0"]))
    
        if(![timer2 isEqualToString:@"0"])
            NSRange range = [timer2 rangeOfString:@"min"];
            NSString *minutes = [timer2 substringToIndex:range.location];

            totalminute = totalminute + [minutes intValue];

            NSNumber* xWrapped = [NSNumber numberWithInt:[minutes intValue]];
            [finaltimerarray addObject:xWrapped];
        
        else
        
            [finaltimerarray addObject:[NSNumber numberWithInt:0]];
        

        // NSLog(@"timer2 minute is = %@",minutes);
    

    else if(([timer2 hasSuffix:@"hours"] || [timer2 hasSuffix:@"hrs"] || [timer2 hasSuffix:@"hour"] || [timer2 hasSuffix:@"hr"]) )
    
        if(![timer2 isEqualToString:@"0"])
        
            NSRange range = [timer2 rangeOfString:@"h"];
            NSString *hours = [timer2 substringToIndex:range.location];
            int minute = [hours intValue] * 60;
            totalminute = totalminute + minute;

            NSNumber* xWrapped = [NSNumber numberWithInt:minute];
            [finaltimerarray addObject:xWrapped];
        
        else
        
            [finaltimerarray addObject:[NSNumber numberWithInt:0]];
        

        //  NSLog(@"timer1 minute is = %@",minutes);
    

    if(([timer3 hasSuffix:@"mins"] || [timer3 hasSuffix:@"minute"] || [timer3 hasSuffix:@"min"]) ||  ([timer3 isEqualToString:@"0"]))
    
        if( ![timer3 isEqualToString:@"0"])
        
            NSRange range = [timer3 rangeOfString:@"min"];
            NSString *minutes = [timer3 substringToIndex:range.location];
            totalminute = totalminute + [minutes intValue];

            NSNumber* xWrapped = [NSNumber numberWithInt:[minutes intValue]];
            [finaltimerarray addObject:xWrapped];
        
        else
        
            [finaltimerarray addObject:[NSNumber numberWithInt:0]];
        

        // NSLog(@"timer3 minute is = %@",minutes);
    
    else if(([timer3 hasSuffix:@"hours"] || [timer3 hasSuffix:@"hrs"] || [timer3 hasSuffix:@"hour"] || [timer3 hasSuffix:@"hr"]) )
    
        if(![timer3 isEqualToString:@"0"])
            NSRange range = [timer3 rangeOfString:@"h"];
            NSString *hours = [timer3 substringToIndex:range.location];
            int minute = [hours intValue] * 60;
            totalminute = totalminute + minute;

            NSNumber* xWrapped = [NSNumber numberWithInt:minute];
            [finaltimerarray addObject:xWrapped];
        
        else
        
            [finaltimerarray addObject:[NSNumber numberWithInt:0]];
        
        //  NSLog(@"timer1 minute is = %@",minutes);
    
    if(([timer4 hasSuffix:@"mins"] || [timer4 hasSuffix:@"minute"] || [timer4 hasSuffix:@"min"]) ||  ([timer4 isEqualToString:@"0"]))
    
        if(![timer4 isEqualToString:@"0"])
        
            NSRange range = [timer4 rangeOfString:@"min"];
            NSString *minutes = [timer4 substringToIndex:range.location];
            totalminute = totalminute + [minutes intValue];

            NSNumber* xWrapped = [NSNumber numberWithInt:[minutes intValue]];
            [finaltimerarray addObject:xWrapped];
        
        else
        
            [finaltimerarray addObject:[NSNumber numberWithInt:0]];
        
        //  NSLog(@"timer4 minute is = %@",minutes);
    
    else if(([timer4 hasSuffix:@"hours"] || [timer4 hasSuffix:@"hrs"] || [timer4 hasSuffix:@"hour"] || [timer4 hasSuffix:@"hr"]) )
    
        if(![timer4 isEqualToString:@"0"])
            NSRange range = [timer4 rangeOfString:@"h"];
            NSString *hours = [timer4 substringToIndex:range.location];
            int minute = [hours intValue] * 60;
            totalminute = totalminute + minute;

            NSNumber* xWrapped = [NSNumber numberWithInt:minute];
            [finaltimerarray addObject:xWrapped];
        
        else
        
            [finaltimerarray addObject:[NSNumber numberWithInt:0]];
        

        //    NSLog(@"timer1 minute is = %@",minutes);
    


    [arrayforshowingdata addObject:finaltimerarray];
    [finaltimerarray release];



for (int i=0; i<[arrayforshowingdata count]; i++)

    NSMutableArray *arraydata = [arrayforshowingdata objectAtIndex:i];

    for (int j=0; j<[arraydata count]; j++)
    
        [arrForStepsReminder addObject:@"0"];
    

    [arrForButtonSelection addObject:@"M"];


lblDisplayTimer.text=@"00:00:00";
lblRecipeName.text=appdelegate.strRecipeName;

currentdate = [NSDate date];
NSDate *timetobefired = appdelegate.timertimetobefired;
timerrecipe = appdelegate.timerrecipename;

if(timerrecipe != nil && ([timerrecipe isEqualToString:appdelegate.strRecipeName]) && timetobefired != nil)


    NSTimeInterval secondsBetween = [timetobefired timeIntervalSinceDate:currentdate];
    NSInteger time = round(secondsBetween);
    int second = (int)time;


    if(second > 0)
    
        secondsLeft = second;
        arrForButtonSelection = appdelegate.storingbuttonstate;

        [btnOnOff setOn:YES];

        if(![timer isValid])
        
            timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(updateCountdown) userInfo:nil repeats:YES];
        
    
    else
    
        secondsLeft = 0;
    


[[NSNotificationCenter defaultCenter]
 addObserver:self
 selector:@selector(goBackground)
 name:UIApplicationDidEnterBackgroundNotification
 object:nil];


 [[NSNotificationCenter defaultCenter]
  addObserver:self
  selector:@selector(doMyLayoutStuff:)
  name: UIApplicationWillEnterForegroundNotification
  object:nil];

【参考方案1】：

在 addObserver 调用中将观察者更改为“self”

即

[[NSNotificationCenter defaultCenter]
  addObserver:self
  selector:@selector(doMyLayoutStuff:)
  name: UIApplicationWillEnterForegroundNotification
  object:nil];

【讨论】：

确保该行正在执行并确保选择器完全相同。粘贴选择器的实现以获取更多回复。

ravi 现在可以正常工作了.. 但现在你能告诉我如何取消注册此通知。

– removeObserver:name:object: 使用它。但在你问之前先搜索一下。