Switching between View Controllers Error

Question

I'm having a bit of an issue here switching between my view controllers.

I followed the advice on this page:

View Controllers: How to switch between views programmatically?

My setup is as follows; I have a splash screen with a button on it and that button loads my second view controller. I have IntroductionViewController as the root view and the button says "Load Website", this Load Website event I want to switch to WebsiteViewController.

On IntroductionViewController I have set up the button as an IBOutlet and IBAction which is NSLogging fine on Click so I know the method is working.

What I need is when you click Load Website it opens WebsiteViewController. What I have so far is credit of the question above:

IntroductionViewController.h

#import <UIKit/UIKit.h>
#import "WebsiteViewController.h"

@class WebsiteViewController;

@interface IntroductionViewController : UIViewController {
    IBOutlet UIButton *websiteButton;
    IBOutlet WebsiteViewController *websiteViewController;
}
@property (nonatomic, retain) UIButton *websiteButton;
@property (nonatomic, retain) WebsiteViewController *websiteViewController;

-(IBAction)loadWebsite:(id)sender;

@end

IntroductionViewController.m

#import "IntroductionViewController.h"

@implementation IntroductionViewController

@synthesize websiteButton;
@synthesize websiteViewController;

-(IBAction)loadWebsite:(id)sender{
    if(self.websiteViewController.view.superview == nil)
    {
        [self.view addSubview:websiteViewController.view];
    }   
}

The line: [self.view addSubview:websiteViewController.view]; doesn't do anything, but as I've said previously, this function is NSLogging fine. I'm not sure how to proceed with this.

Answer 1

Looks like you are not allocating your websiteViewController, without allocating it you have no instance of it to use or reference to it, logging it will simply return null.

I would also try presenting is a ModalViewController if you are not implementing UINavigationController. Here is an example of allocating your webview controller and presenting it as a modalView:

-(IBAction)loadWebsite:(id)sender{
    WebsiteViewController *webView = [[WebsiteViewController alloc] init];
    [self.view presentModalViewController:webView animated:YES];
    [webView release];
}

The default transition style is UIModalTransitionStyleCoverVertical but check out the documentation for more. You can set the transition style like so:

webView.modalTransitionStyle = UIModalTransitionStyleCoverVertical

Answer 2

I bet your WebsiteViewController object hasn't been instantiated. NSLog(@"%@", websiteViewController); I bet its null! :p You need to create the object - I don't know how to do this using interface builder.

Anyway, you're using the old way to switch between view controllers. The new way/ best way is to use a navigation controller to do it like this:

-(IBAction)loadWebsite:(id)sender{
    [self.navigationController pushViewController:websiteViewController animated:YES];  
}

But this won't work unless you've set up a navigation controller, which I don't know how to do in interface builder. This is why I hate interface builder and believe that you should stop learning with it! :p

Without interface builder this is what you should do:

In your app delegate .h file add this at the top:

#include "IntroductionViewController.h"

Then include this with the other @propertys in the code:

@property (nonatomic, retain) UINavigationController *navController;

Now in your app delegate .m file swap the application did finish launching with options with this:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Override point for customization after application launch.
    [self.window makeKeyAndVisible];

    // lets make the navigation controller by setting up a view controller first.
    IntroductionViewController *viewController = [[IntroductionViewController alloc] initWithNibName:nil bundle:nil];
    viewController.title = @"Home";
    navController = [[UINavigationController alloc] initWithRootViewController:viewController];
    [navController setNavigationBarHidden:NO]; // set to yes to hide the title bar
    [viewController release];

    [self.window addSubview:navController.view];

    return YES;
}

That will give you a navigation controller (you can hide the title bar easily... - see the comments). And show the first view controller (IntroductionViewController).

Now running the code I gave you above will work. The [self.navigationController pushViewController:websiteViewController animated:YES];. This gives the viewController to the navigationController and the navigationController does all the adding and removing views and such itself!

And you haven't had to use interface builder at all! :p (well... now you have to learn how to build views without dragging and dropping!).

Anyway... i hope that helped.

Answer 3

Possible you may have forgot to bind the IBOutlet to your WebsiteViewController. And for both Orientation support you can use

 - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOr‌​ientation 
 { 
      // Overriden to allow any orientation. 
      return ((interfaceOrientation==UIInterfaceOrientationLandscapeLeft) || (interfaceOrientation==UIInterfaceOrientationLandscapeRight)); 
 }

One more thought for your orientation problem, you can setFrame to your view while displaying like

 - [yourViewController.view setFrame:CGRectMake(0,0,1024,768)] //iPad and 
 - [yourViewController.view setFrame:CGRectMake(0,0,480,320)] //iPhone.

May be this works.

Thax.