How to calculate keyboard height in iOS? - ios

Question

I know that this question is asked many times, but I can not figure out where am I making mistake. In simple words I can not implement it properly.
I have App which has to work on iPhone and iPad (in portrait orientation only). I have a subclassed UITextField. I need to move it up when it is hidden by keyboard during the edit.
I can not set it properly, because the calculation of the size of the keyboard is done after it enters in the edit mode.
I know that I need following steps:
Register observer
Have routine that calculates Keyboard rectangle from which I can take height
Have 2 events on show and hide of the keyboard to make offset of my custom text field.
Please tell me where I am wrong.
My code is:
Register observer:
- (id)initWithCoder:(NSCoder *)aDecoder{
if (self = [super initWithCoder:aDecoder]) {
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(keyboardWillChange:) name:UIKeyboardWillShowNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(keyboardWillChange:) name:UIKeyboardDidShowNotification object:nil];
_leftInlineImage = NO;
}
return self;
}
Calculating keyboard height:
- (void)keyboardWillChange:(NSNotification *)notification {
NSDictionary* d = [notification userInfo];
CGRect r = [d[UIKeyboardFrameEndUserInfoKey] CGRectValue];
r = [self.superview convertRect:r fromView:nil];
_keyboardHeight = r.size.height;
}
Show/hide keyboard:
/* Move keyboard */
-(void)showKeyboardWithMove {
CGRect screenRect = [[UIScreen mainScreen] bounds];
////CGFloat screenWidth = screenRect.size.width;
CGFloat screenHeight = screenRect.size.height;
//_keyboardHeight = KEYBOARD_HEIGHT;
if (self.frame.origin.y + self.frame.size.height > screenHeight - _keyboardHeight) {
double offset = screenHeight - _keyboardHeight - self.frame.origin.y - self.frame.size.height;
CGRect rect = CGRectMake(0, offset, self.superview.frame.size.width, self.superview.frame.size.height);
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:0.3];
self.superview.frame = rect;
[UIView commitAnimations];
}
}
-(void)hideKeyboardWithMove {
CGRect rect = CGRectMake(0, 0, self.superview.frame.size.width, self.superview.frame.size.height);
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:0.3];
self.superview.frame = rect;
[UIView commitAnimations];
}
The calculation is made before and my height is 0. All this is done in the subclass of the UITextField.

Answer 1

Add an observer of UIKeyboardWillChangeFrameNotification to the viewDidLoad;
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(keyboardFrameDidChange:) name:UIKeyboardWillChangeFrameNotification object:nil];
This method will help you :
- (void)keyboardFrameDidChange:(NSNotification *)notification
{
CGRect keyboardEndFrame = [[[notification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
CGRect keyboardBeginFrame = [[[notification userInfo] objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue];
UIViewAnimationCurve animationCurve = [[[notification userInfo] objectForKey:UIKeyboardAnimationCurveUserInfoKey] integerValue];
NSTimeInterval animationDuration = [[[notification userInfo] objectForKey:UIKeyboardAnimationDurationUserInfoKey] integerValue];
[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:animationDuration];
[UIView setAnimationCurve:animationCurve];
CGRect newFrame = self.view.frame;
CGRect keyboardFrameEnd = [self.view convertRect:keyboardEndFrame toView:nil];
CGRect keyboardFrameBegin = [self.view convertRect:keyboardBeginFrame toView:nil];
newFrame.origin.y -= (keyboardFrameBegin.origin.y - keyboardFrameEnd.origin.y);
self.view.frame = newFrame;
[UIView commitAnimations];
}

Answer 2

that gives you back the height of the keyboard.
NSNotification * note = // ... the notification you receive via UIKeyboardWillShowNotification
id _obj = [note.userInfo valueForKey:#"UIKeyboardBoundsUserInfoKey"];
CGRect _keyboardBound = CGRectNull;
if ([_obj respondsToSelector:#selector(getValue:)]) [_obj getValue:&_keyboardBound];
the _keyboardBound will have the correct size.
NOTE: that is not a full implementation to handle the keyboard's appearance, if you need the complex idea, please check my complete and accepted answer here (stackoverflow.com internal link).