iOS 中判断应用程序是否为第一次打开

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    //NSUserDefaults非常好用，并不需要用户在程序中设置NSUserDefaults的全局变量，需要在哪里使用NSUserDefaults的数据，那么就在哪里创建一个NSUserDefaults对象，然后进行读或者写操作。
    if (![[NSUserDefaults standardUserDefaults]boolForKey:@"everLaunched"]) {
        [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"everLaunched"];
        [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"firstLaunch"];
    }else{
         [[NSUserDefaults standardUserDefaults] setBool:NO forKey:@"firstLaunch"]; 
    }
    // Override point for customization after application launch.
    return YES;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    if ([[NSUserDefaults standardUserDefaults] boolForKey:@"firstLaunch"]) {
        // 这里判断是否第一次
        UIAlertView *alert=[[UIAlertView alloc] initWithTitle:@"第一次"
                                                      message:@"进入App"
                                                     delegate:self
                                            cancelButtonTitle:@"我知道了"
                                            otherButtonTitles:nil];
        [alert show];//使用UIAlertView显示应用是否为第一次启动
    }
}