Question

I am stumped by the Facebook API for logging in. I can’t find anything helpful on the net.

My FBSessionDelegate methods are not being called, and accessToken and expirationDate values are not being set, so I don’t think I am ever logged in.

I reverted to a very simple app, with only two buttons (log in, log out) and a label to see status information.

Here is the code for the view controller, where all the processing takes place:

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

@interface facebook_login_testViewController : UIViewController <FBSessionDelegate>{

    UIButton *loginButton;
    UIButton *logoutButton;
    UILabel *info;

    Facebook *facebook;

}

@property (nonatomic, retain) Facebook *facebook;

- (void) loggingIn;
- (void) loggingOut;

@end

and

#import "facebook_login_testViewController.h"

@implementation facebook_login_testViewController
@synthesize facebook;

- (void)dealloc
{
    [super dealloc];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
}

#pragma mark - View lifecycle

- (void)viewDidLoad
{
    [super viewDidLoad];

    loginButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [loginButton setTitle: @"Log In" forState:UIControlStateNormal];
    [loginButton addTarget:self action:@selector(loggingIn) forControlEvents:UIControlEventTouchUpInside];
    loginButton.frame = CGRectMake(200, 200, 200, 50);

    logoutButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [logoutButton setTitle: @"Log Out" forState:UIControlStateNormal];
    [logoutButton addTarget:self action:@selector(loggingOut) forControlEvents:UIControlEventTouchUpInside];
    logoutButton.frame = CGRectMake(200, 300, 200, 50);

    info = [[UILabel alloc] initWithFrame:CGRectMake(200, 400, 400, 600)];
    info.numberOfLines = 0;

    [self.view addSubview:loginButton];
    [self.view addSubview:logoutButton];
    [self.view addSubview:info];

    info.text = @"Waiting to log in...\n\nPress the login button.";

    facebook = [[Facebook alloc] initWithAppId:@"159...........5" andDelegate:self];

    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    if ([defaults objectForKey:@"FBAccessTokenKey"] 
        && [defaults objectForKey:@"FBExpirationDateKey"]) {
        facebook.accessToken = [defaults objectForKey:@"FBAccessTokenKey"];
        facebook.expirationDate = [defaults objectForKey:@"FBExpirationDateKey"];
    }

}


- (void)viewDidUnload
{
    [super viewDidUnload];        
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    // Return YES for supported orientations
    return YES;
}

- (void) loggingIn{
    if (![facebook isSessionValid]) {
        [facebook authorize:nil];
    }
}

- (void) loggingOut{
    info.text = [NSString stringWithFormat:@"\naccess token: %@\nexpiration date: %@\nfacebood description:%@\n",facebook.accessToken, facebook.expirationDate, facebook];
    [facebook logout:self];

}

- (BOOL)application:(UIApplication *)application handleOpenURL:(NSURL *)url {

    return [facebook handleOpenURL:url]; 
}

- (void)fbDidLogin {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    [defaults setObject:[facebook accessToken] forKey:@"FBAccessTokenKey"];
    [defaults setObject:[facebook expirationDate] forKey:@"FBExpirationDateKey"];
    [defaults synchronize];

}

@end

The .plist file is set up like this

This really looks too simple to get wrong. When I click the login button, I can trace through authorize:permission, and then authorize:permissions localAppId:localAppId, and as far as I can trace it, I don’t see anything that looks like it’s going to results in isSessionValid becoming TRUE.

I wait and then press the log off button, and take a look at some Facebook parameters, in case something asynchronous needed to occur, and they are still null.

Can someone see what I am missing?

Answer 1

There are few examples on the net that show how this works, but the Facebook SDK is distributed with a demo app (DemoApp) that works once you plug in the appId. (If you don’t plug in the appId value, it will get killed when it checks for that value.)

What is happening in the authorization process is that [facebook authorize:permissions] is called. (permissions should not be nil)

This leads to a call to [self authorize:permissions localAppId:nil], which then calls [self authorizeWithFBAppAuth:YES safariAuth:YES]. In that method, three ways of connecting to facebook for authorization can be tried.

In each of these asynchronous methods, the application delegate is the delegate that handles the resulting callback as part of the to application:(UIApplication *)application handleOpenURL:(NSURL *)url. If this was mentioned in the other online tutorials, it’s easy to miss, because they generally do all of the processing within the application delegate, from what I saw. In my case, I did the main processing within the main view controller.

The fix, in my case, was to move the application:(UIApplication *)application handleOpenURL:(NSURL *)url method to the application delegate and point it to the facebook object like this:

- (BOOL)application:(UIApplication *)application handleOpenURL:(NSURL *)url {
  return [[controller facebook] handleOpenURL:url];
}

After that, the other facebook delegate methods (fbDidLogin, fbDidLogout) were called and I received the accessToken and expirationDate. So it looks like this is working now.