Moving views around when the keyboard shows in iOS

When the keyboard shows or hides in iOS, we receive an event to notify us that the keyboard is being shown and being hidden.

Ideally we want to get the animation parameters and the size of that keyboard so we can rearrange the views inside of our application to fit the keyboard. I’m only covering the case of the keyboard on the iPhone; on the iPad you also have the problem of the split keyboard, but the same ideas should hold there as well.

Step 1:

When the view controller that may show a keyboard appears, register for notifications for the keyboard being shown and hidden:

- (void)viewDidLoad
    [super viewDidLoad];

	// Do any additional setup after loading the view.
	[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardShowHide:) name:UIKeyboardWillShowNotification object:nil];
	[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardShowHide:) name:UIKeyboardWillHideNotification object:nil];

	// other stuff here

Step 2:

Remember to unregister notifications when this goes away, to prevent problems.

- (void)dealloc
	[[NSNotificationCenter defaultCenter] removeObserver:self];

Step 3:

Receive the event in our new method, and extract the keyboard parameters and animation parameters.

- (void)keyboardShowHide:(NSNotification *)n
	CGRect krect;

	/* Extract the size of the keyboard when the animation stops */
	krect = [n.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];

	/* Convert that to the rectangle in our primary view. Note the raw
	 * keyboard size from above is in the window's frame, which could be
	 * turned on its side.
	krect = [self.view convertRect:krect fromView:nil];

	/* Get the animation duration, and animation curve */
	NSTimeInterval duration = [[n.userInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];
	UIViewAnimationCurve curve = [[n.userInfo objectForKey:UIKeyboardAnimationCurveUserInfoKey] intValue];

	/* Kick off the animation. What you do with the keyboard size is up to you */
	[UIView animateWithDuration:0 delay:duration options:UIViewAnimationOptionBeginFromCurrentState | curve animations:^{
			/* Set up the destination rectangle sizes given the keyboard size */
			Do something interesting here
		} completion:^(BOOL finished) {
			/* Finish up here */
			Do something interesting here

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