facebook-ios-sdk - 尽管通过 FBSDKLoginButton 登录，但 ios Facebook SDK v4.x 访问 token 为 null

Question

尽管按钮显示我已登录，但我的 facebook 访问 token 为空。有人知道为什么会这样吗？

从 RootViewController.m

- (void)viewDidLoad {
    [super viewDidLoad];

    self->login_button = [[FBSDKLoginButton alloc] init];
    self->login_button.center = self.view.center;
    [self.view addSubview:self->login_button];

    FBSDKAccessToken* access_token =[FBSDKAccessToken currentAccessToken];
    NSLog(@"Access Token, %@",access_token);
}

来自 ApplicationDelegate.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    [self.window setRootViewController:[[RootViewController alloc] init]];

    [self.window makeKeyAndVisible];

    [self.window setBackgroundColor:[UIColor purpleColor]];
    [FBSDKLoginButton class];
    return [[FBSDKApplicationDelegate sharedInstance] application:application didFinishLaunchingWithOptions:launchOptions];
}

我的 -ObjC 链接器标志也已设置

Answer 1

需要首先调用 FBSDKApplicationDelegate 来解析缓存的 token 。由于您正在立即设置根 View Controller ，因此会在 FBSDKApplicationDelegate 之前调用您的 viewDidLoad。相反，您可以将 FBSDKApplicationDelegate 向上移动:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
  // Override point for customization after application launch.
  [FBSDKLoginButton class];
  BOOL r = [[FBSDKApplicationDelegate sharedInstance] application:application didFinishLaunchingWithOptions:launchOptions];

  self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

  [self.window setRootViewController:[[RootViewController alloc] init]];

  [self.window makeKeyAndVisible];

  [self.window setBackgroundColor:[UIColor purpleColor]];


  return r;
}