从后台打开应用程序时不调用 ViewDidAppear

小编典典

从后台打开应用程序时不调用 ViewDidAppear

all

我有一个视图控制器，其中我的值为
0（标签），当我从另一个视图控制器打开该视图控制器时，ViewController我已将viewDidAppear标签上的值设置为
20。它工作正常，但是当我关闭我的应用程序并再次打开我的应用程序但值没有改变viewDidLoad，因为没有任何viewDidAppear东西viewWillAppear被调用。打开我的应用程序时如何拨打电话。我必须做任何事情applicationDidBecomeActive吗？

阅读 56

2022-08-08

共1个答案

小编典典

对事件的确切顺序感到好奇，我按如下方式检测了一个应用程序：（@Zohaib，您可以使用下面的 NSNotificationCenter
代码来回答您的问题）。

// AppDelegate.m

- (void)applicationWillEnterForeground:(UIApplication *)application
{
    NSLog(@"app will enter foreground");
}

- (void)applicationDidBecomeActive:(UIApplication *)application
{
    NSLog(@"app did become active");
}

// ViewController.m

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSLog(@"view did load");

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(appDidBecomeActive:) name:UIApplicationDidBecomeActiveNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(appWillEnterForeground:) name:UIApplicationWillEnterForegroundNotification object:nil];
}

- (void)appDidBecomeActive:(NSNotification *)notification {
    NSLog(@"did become active notification");
}

- (void)appWillEnterForeground:(NSNotification *)notification {
    NSLog(@"will enter foreground notification");
}

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    NSLog(@"view will appear");
}

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    NSLog(@"view did appear");
}

启动时，输出如下所示：

2013-04-07 09:31:06.505 myapp[15459:11303] view did load
2013-04-07 09:31:06.507 myapp[15459:11303] view will appear
2013-04-07 09:31:06.511 myapp[15459:11303] app did become active
2013-04-07 09:31:06.512 myapp[15459:11303] did become active notification
2013-04-07 09:31:06.517 myapp[15459:11303] view did appear

进入后台，然后重新进入前台：

2013-04-07 09:32:05.923 myapp[15459:11303] app will enter foreground
2013-04-07 09:32:05.924 myapp[15459:11303] will enter foreground notification
2013-04-07 09:32:05.925 myapp[15459:11303] app did become active
2013-04-07 09:32:05.926 myapp[15459:11303] did become active notification

2022-08-08