frénésie frénésie - 5 months ago 30
iOS Question

How do I scroll the UIScrollView when the keyboard appears?

I'm having trouble with my code. I'm trying to move the

UIScrollView
when I'm editing an
UITextField
that should be hidden by the keyboard pop.

I'm moving the main frame right now because I don't know how to 'scroll up' in the code.
So, I did a little bit of code, it's working fine but when I edit an UItextfield and I switch to another
UITextField
without pressing on the 'return' button the main view goes waaayyyyy to far up.

I did an
NSLog()
with my variables size, distance and textFieldRect.origin.y as you can see below. When I put two
UITextField
at the same place (y origin) and I do this particular 'switch' (wihtout pressing return) , I get the same numbers, whereas my code worked fine for the first
UITextField
editing but not for the second editing.

Check this out:

- (void)textFieldDidBeginEditing:(UITextField *)textField {
{
int size;
CGRect textFieldRect = [self.view.window convertRect:textField.bounds fromView:textField];
size = textFieldRect.origin.y + textFieldRect.size.height;
if (change == FALSE)
{
size = size - distance;
}
if (size < PORTRAIT_KEYBOARD_HEIGHT)
{
distance = 0;
}
else if (size > PORTRAIT_KEYBOARD_HEIGHT)
{
distance = size - PORTRAIT_KEYBOARD_HEIGHT + 5; // +5 px for more visibility
}
NSLog(@"origin %f", textFieldRect.origin.y);
NSLog(@"size %d", size);
NSLog(@"distance %d", distance);
CGRect viewFrame = self.view.frame;
viewFrame.origin.y -= distance;
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationBeginsFromCurrentState:YES];
[UIView setAnimationDuration:KEYBOARD_ANIMATION_DURATION];
[self.view setFrame:viewFrame];
[UIView commitAnimations];
change = FALSE;
}

- (void)textFieldDidEndEditing:(UITextField *)textField
{
change = TRUE;
CGRect viewFrame = self.view.frame;
viewFrame.origin.y += distance;
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationBeginsFromCurrentState:YES];
[UIView setAnimationDuration:KEYBOARD_ANIMATION_DURATION];
[self.view setFrame:viewFrame];
[UIView commitAnimations];
}


Any ideas ?

Answer

The recommended way from Apple is to change the contentInset of the UIScrollView. It is a very elegant solution, because you do not have to mess with the contentSize. Following code is copied from the Keyboard Programming Guide, where the handling of this issue is explained. You should have a look into it.

// Call this method somewhere in your view controller setup code.
- (void)registerForKeyboardNotifications
{
    [[NSNotificationCenter defaultCenter] addObserver:self
            selector:@selector(keyboardWasShown:)
            name:UIKeyboardDidShowNotification object:nil];
   [[NSNotificationCenter defaultCenter] addObserver:self
             selector:@selector(keyboardWillBeHidden:)
             name:UIKeyboardWillHideNotification object:nil];
}

// Called when the UIKeyboardDidShowNotification is sent.
- (void)keyboardWasShown:(NSNotification*)aNotification
{
    NSDictionary* info = [aNotification userInfo];
    CGSize kbSize = [[info objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;
    UIEdgeInsets contentInsets = UIEdgeInsetsMake(0.0, 0.0, kbSize.height, 0.0);
    scrollView.contentInset = contentInsets;
    scrollView.scrollIndicatorInsets = contentInsets;

    // If active text field is hidden by keyboard, scroll it so it's visible
    // Your application might not need or want this behavior.
    CGRect aRect = self.view.frame;
    aRect.size.height -= kbSize.height;
    if (!CGRectContainsPoint(aRect, activeField.frame.origin) ) {
        CGPoint scrollPoint = CGPointMake(0.0, activeField.frame.origin.y-kbSize.height);
        [scrollView setContentOffset:scrollPoint animated:YES];
    }
}

// Called when the UIKeyboardWillHideNotification is sent    
- (void)keyboardWillBeHidden:(NSNotification*)aNotification
{
    UIEdgeInsets contentInsets = UIEdgeInsetsZero;
    scrollView.contentInset = contentInsets;
    scrollView.scrollIndicatorInsets = contentInsets;
}