iOS: Scaling UITextView with pinching?

Question

I'm interested in creating UITextView that is expanding dynamically while typing the text, and scaling as the user pinches the screen(Similar behaviour can be found in TinyPost).

When you just type (without pinching) the textView expands fine. When you just pinch (without typing) is works fine, but when you pinch and then type, the text inside gets cut.

Here is my code:

UIPinchGestureRecognizer *pinchGestRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(scaleTextView:)];
        pinchGestRecognizer.delegate = self;
        [bgFrameImageView addGestureRecognizer:pinchGestRecognizer];

    - (void)scaleTextView:(UIPinchGestureRecognizer *)pinchGestRecognizer{
        createTextView.transform = CGAffineTransformScale(createTextView.transform, pinchGestRecognizer.scale, pinchGestRecognizer.scale);

        pinchGestRecognizer.scale = 1;        
    }

    - (void)textViewDidChange:(UITextView *)textView{

        CGSize textSize = textView.contentSize;

        textView.frame = CGRectMake(CGRectGetMinX(textView.frame), CGRectGetMinY(textView.frame), textSize.width, textSize.height); //update the size of the textView  
    }

What do you think?

Answer 1

Try:

- (void)scaleTextView:(UIPinchGestureRecognizer *)pinchGestRecognizer{
     CGFloat scale = pinchGestRecognizer.scale;

    createTextView.font = [UIFont fontWithName:createTextView.font.fontName size:createTextView.font.pointSize*scale];

    [self textViewDidChange:createTextView];       
}

It basically scales the font size and then recalculates the content size using your code in textViewDidChange.

Answer 2

To elaborate on @Cocoanetics answer above. I implemented the gesture handling idea for attributed strings on iOS 7 but it is prohibitively slow when you have too many font changes in your string. There is also a ridiculous buffering bug in iOS 7 where Change notifications keep firing long after you've stopped pinching - reminds me of the stupid keyboard buffer in early versions of PC-DOS. Anyway, I have put the code below that got this working for me - although it has only resulted in informing me that this is a waste of time and that I need to give my users some other way of scaling their fonts.

- (void)scaleTextView:(UIPinchGestureRecognizer *)pinchGestureRecognizer
{
    CGFloat scale = 0;
    NSMutableAttributedString *string;

    switch (pinchGestureRecognizer.state) {
        case UIGestureRecognizerStateBegan:
            self.old_scale = 1.0;
            self.last_time = [NSDate date];
            break;

        case UIGestureRecognizerStateChanged:
            scale = pinchGestureRecognizer.scale - self.old_scale;

            if( [self.last_time timeIntervalSinceNow] < -0.2 )  {       //  updating 5 times a second is best I can do - faster than this and we get buffered changes going on for ages!
                self.last_time = [NSDate date];
                string = [self getScaledStringFrom:[self.textview.attributedText mutableCopy] withScale:1.0 + scale];
                if( string )    {
                    self.textview.attributedText = string;
                    self.old_scale = pinchGestureRecognizer.scale;
                }
            }
            break;

        case UIGestureRecognizerStateEnded:
        case UIGestureRecognizerStateCancelled:
        case UIGestureRecognizerStateFailed:
            break;

        default:
            break;
    }
}

- (NSMutableAttributedString*) getScaledStringFrom:(NSMutableAttributedString*)string withScale:(CGFloat)scale
{
    [string beginEditing];
    [string enumerateAttribute:NSFontAttributeName inRange:NSMakeRange(0, string.length) options:0 usingBlock:^(id value, NSRange range, BOOL *stop) {
        if (value) {
            UIFont *oldFont = (UIFont *)value;
            UIFont *newFont = [oldFont fontWithSize:oldFont.pointSize * scale];
            [string removeAttribute:NSFontAttributeName range:range];
            [string addAttribute:NSFontAttributeName value:newFont range:range];
        }
    }];
    [string endEditing];
    return string;
}