In Custom Keyboard Extension , we can't use
`didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation` 
and sharedApplication.
I need to detect portrait or landscape in keyboard when rotate.
How can i detect when orientation change in Custom Keyboard extension?
In order to update your custom keyboard when the orientation changes, override viewDidLayoutSubviews in the UIInputViewController. As far as I can tell, when a rotation occurs this method is always called.
Additionally, as the traditional [UIApplication sharedApplication] statusBarOrientation] doesn't work, to determine the current orientation use the following snippet:
if([UIScreen mainScreen].bounds.size.width < [UIScreen mainScreen].bounds.size.height){
    //Keyboard is in Portrait
}
else{
    //Keyboard is in Landscape
}
Hopefully this helps!
Non-deprecated and will work on any device screen size (including future screen sizes Apple will be releasing this year).
In CustomKeyboardViewController.m:
-(void)viewDidLayoutSubviews {
    NSLog(@"%@", (self.view.frame.size.width == ([[UIScreen mainScreen] bounds].size.width*([[UIScreen mainScreen] bounds].size.width<[[UIScreen mainScreen] bounds].size.height))+([[UIScreen mainScreen] bounds].size.height*([[UIScreen mainScreen] bounds].size.width>[[UIScreen mainScreen] bounds].size.height))) ? @"Portrait" : @"Landscape");
}
done.
Or.................. 
For a more easy to read version of this code:
-(void)viewDidLayoutSubviews {
    int appExtensionWidth = (int)round(self.view.frame.size.width);
    int possibleScreenWidthValue1 = (int)round([[UIScreen mainScreen] bounds].size.width);
    int possibleScreenWidthValue2 = (int)round([[UIScreen mainScreen] bounds].size.height);
    int screenWidthValue;
    if (possibleScreenWidthValue1 < possibleScreenWidthValue2) {
        screenWidthValue = possibleScreenWidthValue1;
    } else {
        screenWidthValue = possibleScreenWidthValue2;
    }
    if (appExtensionWidth == screenWidthValue) {
        NSLog(@"portrait");
    } else {
        NSLog(@"landscape");
    }
}
There is a simple way, just looking at the screen width:
 double width = [[UIScreen mainScreen] bounds].size.width;
 double interfaceWidth = MIN([[UIScreen mainScreen] bounds].size.width, [[UIScreen mainScreen] bounds].size.height);
 BOOL isPortrait = (width == interfaceWidth) ? YES : NO;
use viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:
inside your viewController
- (void)updateViewConstraints {
    [super updateViewConstraints];
    // Add custom view sizing constraints here
    if (self.view.frame.size.width == 0 || self.view.frame.size.height == 0)
        return;
    [self.inputView removeConstraint:self.heightConstraint];
    CGSize screenSize = [[UIScreen mainScreen] bounds].size;
    CGFloat screenH = screenSize.height;
    CGFloat screenW = screenSize.width;
    BOOL isLandscape =  !(self.view.frame.size.width ==
                      (screenW*(screenW<screenH))+(screenH*(screenW>screenH)));
    NSLog(isLandscape ? @"Screen: Landscape" : @"Screen: Potriaint");
    self.isLandscape = isLandscape;
    if (isLandscape) {
        self.heightConstraint.constant = self.landscapeHeight;
        [self.inputView addConstraint:self.heightConstraint];
    } else {
        self.heightConstraint.constant = self.portraitHeight;
        [self.inputView addConstraint:self.heightConstraint];
    }
    //trigger default first view
    [btn_gif sendActionsForControlEvents: UIControlEventTouchUpInside];
}
willRotateToInterfaceOrientation and didRotateFromInterfaceOrientation can be used, I just tried this on my iPad running a keyboard on iOS 8.1. Note that those are deprecated in iOS 8, but their replacement, willTransitionToTraitCollection, isn't called though likely because the trait collection doesn't change for the keyboard upon rotation.
Before iOS 8.3, you have to use
-(void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation
                               duration:(NSTimeInterval)duration
This one does not work (it should be a bug):
-(void)viewWillTransitionToSize:(CGSize)size
      withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator
On iOS 8.3 and later, you'd better use
-(void)viewWillTransitionToSize:(CGSize)size
      withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator
because
-(void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation
                               duration:(NSTimeInterval)duration
is deprecated.
In somecase [UIScreen mainscreen].bounds may not work. Sometimes it will update after viewWillTransitionToSize:
Try this
- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator{
    CGSize screenSize = [[UIScreen mainScreen] bounds].size;
    CGFloat realScreenHeight = MAX(screenSize.height, screenSize.width);
    if(size.width == realScreenHeight)
        NSLog(@"Landscape");
    else
        NSLog(@"Portrait");
}
      - (void) viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator 
    {   
     [coordinator animateAlongsideTransition:^(id<UIViewControllerTransitionCoordinatorContext> context) 
        {      UIInterfaceOrientation orientation = [[UIApplication sharedApplication] statusBarOrientation];      // do whatever 
          } completion:^(id<UIViewControllerTransitionCoordinatorContext> context) {    }];       [super viewWillTransitionToSize: size withTransitionCoordinator: coordinator]; 
 }
来源:https://stackoverflow.com/questions/24166878/how-to-detect-orientation-change-in-custom-keyboard-extension-in-ios-8