当应用程序激活时，显示iPhone的登录屏幕

Question

从其他线程到这里我得到了一个模态视图“登录屏幕”，以便在我的应用程序第一次启动时显示。我现在想要的是让应用程序重新进入前台时显示登录屏幕（即它在后台运行并再次启动），以便用户可以重新登录。

这是来自applicationDidFinishLaunchingWithOptions

的代码

LoginViewController *loginViewController = [[LoginViewController alloc] initWithNibName:@"LoginView" bundle:nil];


    if (lockScreenOnOff) 
    {
        [self.tabBarController presentModalViewController:loginViewController animated:YES];
        [self.window makeKeyAndVisible];
    }

如果开关（lockScreenOnOff）打开，则显示模态登录视图。我怎么能做到这一点？

Answer 1

在您的应用程序委托中实施applicationDidEnterBackground:和applicationDidBecomeActive:。 （UIApplicationDelegate class reference）

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Create all view controllers

    [self lockApplicationAnimated:NO]; // Lock on launching
    [self.window makeKeyAndVisible];

    return YES;
}

- (void)lockApplicationAnimated:(BOOL)animated
{
    [self.tabBarController presentModalViewController:self.loginViewController
                                             animated:animated];
}

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    // Lock the application
    // Also, save all user data because the application might terminate soon
    [self lockApplicationAnimated:NO];
}

- (void)applicationDidBecomeActive:(UIApplication *)application
{
    // Hooray, the user returned!
    // Screen should be locked because the applicationDidEnterBackground
}

此外，您还可以使用NSTimer在一段时间后使会话无效。