Got a keyboard will show notification, but keyboard window is nil - ios

Question

I am a little bit confused. I am creating an App where user can swipe a scrollview horizontally between pages and every page has a textfield or a textview. I subscribe to UIKeyboardWillShowNotification and UIKeyboardWillHideNotification notifications and cards decrease their height when keyboard pops up and increase it back when keyboard hides.
Also when scrollView is dragged all textViews/textField resign first responder. That is how it looks like:
-(void)keyboardWillHide:(NSNotification*)notification{
// NSLog(#"notification user info = %#",notification.userInfo);
auto userInfo=notification.userInfo;
auto curve=[userInfo[UIKeyboardAnimationCurveUserInfoKey] unsignedIntegerValue];
auto duration=[userInfo[UIKeyboardAnimationDurationUserInfoKey] doubleValue];
auto startFrame=[userInfo[UIKeyboardFrameBeginUserInfoKey] CGRectValue];
auto endFrame=[userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];
auto dY=endFrame.origin.y-startFrame.origin.y;
[UIView beginAnimations:nil context:nil];
[UIView setAnimationCurve:(UIViewAnimationCurve)curve];
[UIView setAnimationDuration:duration];
_feedbackTextView.height+=dY;
_feedbackUserDataView.height+=dY;
[UIView commitAnimations];
}
-(void)keyboardWillShow:(NSNotification *)notification{
// NSLog(#"notification user info = %#",notification.userInfo);
auto userInfo=notification.userInfo;
auto curve=[userInfo[UIKeyboardAnimationCurveUserInfoKey] unsignedIntegerValue];
auto duration=[userInfo[UIKeyboardAnimationDurationUserInfoKey] doubleValue];
auto startFrame=[userInfo[UIKeyboardFrameBeginUserInfoKey] CGRectValue];
auto endFrame=[userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];
auto dY=endFrame.origin.y-startFrame.origin.y;
[UIView beginAnimations:nil context:nil];
[UIView setAnimationCurve:(UIViewAnimationCurve)curve];
[UIView setAnimationDuration:duration];
_feedbackTextView.height+=dY;
_feedbackUserDataView.height+=dY;
[UIView commitAnimations];
}
-(void)scrollViewDidScroll:(UIScrollView *)scrollView{
[_feedbackTextView resignFirstResponder];
[_feedbackUserDataView resignFirstResponder];
}
-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
// NSLog(#"%s",sel_getName(_cmd));
CGFloat width = scrollView.frame.size.width;
NSInteger page = (scrollView.contentOffset.x + (0.5f * width)) / width;
switch(page){
case 0:{
[_feedbackTextView becomeFirstResponder];
}break;
case 1:{
[_feedbackUserDataView becomeFirstResponder];
}break;
}
}
-(void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{
// NSLog(#"decelerate = %d",decelerate);
if(decelerate==NO){
CGFloat width = scrollView.frame.size.width;
NSInteger page = (scrollView.contentOffset.x + (0.5f * width)) / width;
switch(page){
case 0:{
[_feedbackTextView becomeFirstResponder];
}break;
case 1:{
[_feedbackUserDataView becomeFirstResponder];
}break;
}
}
}
_feedbackTextView is a subview on the first page of scrollView, _feedbackUserDataView is a subview on the second page of scrollView.
I tested my App. I scrolled, tapped textViews/textFields chaotically. And I got warning in my logs
|warning| Got a keyboard will show notification, but keyboard window is nil.
To my surprise there is nothing about this in google so I posted a question here. Sorry for ugly formatting.

Answer 1

This warning seems to be generated when the keyboard is dismissed immediately after being presented, before the animation has been completed.
In this case scrollViewDidEndDecelerating: can get called when the user starts panning again while the scroll view is still decelerating. Then immediately afterwards scrollViewDidScroll: gets called, which results in the keyboard being presented and immediately dismissed.
One fix would be to check the scrollView's panGestureRecogniser state and avoid making the text field first responder if it's in UIGestureRecognizerStateBegan
-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
if ([scrollView panGestureRecognizer].state == UIGestureRecognizerStateBegan) {
return;
}
// NSLog(#"%s",sel_getName(_cmd));
CGFloat width = scrollView.frame.size.width;
NSInteger page = (scrollView.contentOffset.x + (0.5f * width)) / width;
switch(page){
case 0:{
[_feedbackTextView becomeFirstResponder];
}break;
case 1:{
[_feedbackUserDataView becomeFirstResponder];
}break;
}
}
This should remove most of the warnings. There may still be some if the user starts panning just as the keyboard is being presented. These would be harder to deal with - you'd need to make sure the keyboard has finished it's presentation animation before dismissing it by also subscribing to the UIKeyboardDidShowNotification and dismissing it there if the user is panning.