UIButton不会打开新的视图控制器

Question

I am having trouble getting a new view controller to show on the screen when the button is pressed. I created a subclass of UIViewController named StartUpVC . I added it to the app delegate.m and created an instance of StartupVC *startUpVC = [StartUpVC new] and then set self.window.rootViewController = startUpVC; . So now in the StartUpVC class, I created a button so a user can log in with a UIImageView in the background. Now when the button is pressed, it doesn't open up the view controller for the log in screen and does nothing. So my question is how do i get it to open that view controller? Or should it simply be a UIView that opens when the button is pressed?

This is in the StartUpVC.m

- (void)viewDidLoad
{
    [super viewDidLoad];
 ...Code Irrelevant to the question here...

//Create Log In Button
    UIButton *logInButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    logInButton.frame = CGRectMake(20, 480, 280, 40);
    logInButton.layer.cornerRadius = 4.0f;
    logInButton.layer.opacity = .6;
    logInButton.backgroundColor = [UIColor lightGrayColor];
    [logInButton setTitle:@"Log In" forState:UIControlStateNormal];
    [logInButton setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];
    [logInButton setTitleColor:[UIColor blackColor] forState:UIControlStateHighlighted];
    [logInButton addTarget:self action:@selector(sendToLogInScreen:) forControlEvents:UIControlEventTouchUpInside];


    [self.view addSubview:logInButton];

}

-(void)sendToLogInScreen:(id)sender {

    LogInVC *logIn = [LogInVC new];

    [self presentViewController:logIn animated:YES completion:nil];

}

Answer 1

First thing you need to know is whether the method sendToLogInScreen is getting called at all. Place a breakpoint anywhere in the function to check.

Once you know whether the function is getting called at the proper time or not, this problem will either be about:

• sendToLogInScreen is not getting called
  • Something is wrong with the button
    • it's nil
    • the gesture isn't setup properly
  • UserInteraction is disabled for StartupVC 's view property
• sendToLogInScreen is getting called
  • logIn is nil
  • presentViewController is failing for some reason

Hope that helps you figure out what might be causing the issue.