ios - 当应用程序从后台带到前台时如何制作 UIAlertView

Question

目前我在 viewDidLoad 上显示一个 UIAlertView，但是一旦它进入后台并重新启动，它就不会再次出现。我该如何解决这个问题？我需要哪些代表，我该怎么做？

- (void)viewDidLoad {
    [super viewDidLoad];
    UIAlertView *myAlert = [[UIAlertView alloc]initWithTitle:@"Alert!" message:@"This is an Alert!" delegate:nil cancelButtonTitle:@"Cancel!" otherButtonTitles:nil, nil];
    [myAlert show];
}

Answer 1

苹果文档:UIApplicationDidBecomeActiveNotification

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];

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


- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];

    // don't forget remove it
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationDidBecomeActiveNotification object:nil];
}

- (void)yourMethod
{
    UIAlertView *myAlert = [[UIAlertView alloc]initWithTitle:@"Alert!" message:@"This is an Alert!" delegate:nil cancelButtonTitle:@"Cancel!" otherButtonTitles:nil, nil];
    [myAlert show];
}