Facebook SDK 4.0 iOS 不再快速切换到设备上安装的 Facebook APP

FBSDKLoginManager *login = [[FBSDKLoginManager alloc] init];
    [login logInWithReadPermissions:@[self.requiredPermission]
                 fromViewController:self
                            handler:^(FBSDKLoginManagerLoginResult *result, NSError *error) {
        if ([result.grantedPermissions containsObject:self.requiredPermission]) {
          NSLog (@"Sucess!");
        } else {
            [self dismissViewControllerAnimated:YES completion:NULL];
        }
    }];

FBSDKLoginManager *login = [[FBSDKLoginManager alloc] init];

typedef NS_ENUM(NSUInteger, FBSDKLoginBehavior)
{
/*!
   not installed on the device, falls back to //c FBSDKLoginBehaviorBrowser. This is the
default behavior.
*/

   FBSDKLoginBehaviorNative = 0,

/*!
   @abstract Attempts log in through the Safari browser
*/

   FBSDKLoginBehaviorBrowser,

/*!
   @abstract Attempts log in through the Facebook account currently signed in through
   the device Settings.
   @note If the account is not available to the app (either not configured by user or
   as determined by the SDK) this behavior falls back to //c FBSDKLoginBehaviorNative.
 */

   FBSDKLoginBehaviorSystemAccount,

/*!
   @abstract Attemps log in through a modal //c UIWebView pop up
   @note This behavior is only available to certain types of apps. Please check the Facebook
   Platform Policy to verify your app meets the restrictions.
*/

   FBSDKLoginBehaviorWeb,
};