Grow a UIImageView while UILongPressGestureRecognizer active

Question 1

A timer may not be smooth. Instead check out CADisplayLink, which will provide a delegate callback whenever the device's screen is redrawn (~60hz), so you will get a per frame chance to adjust your balloon size.

Another thing to consider is the time between refreshes isn't constant, it could be a lot slower than when the last refresh occured, so if you are incrementing the size by a constant 15 every time you get a callback, then the animation may not seem smooth.

To combat this, when you start the animation take a timestamp and hold onto it, then when you inflate the balloon take another timestamp and determine the difference between now and the last redraw, then multiply the difference by some value, which will ensure a constant smooth size growth - this is called a timestep.

https://developer.apple.com/library/ios/documentation/QuartzCore/Reference/CADisplayLink_ClassRef/Reference/Reference.html

Question 2

Getting creative here, but I think this might work: You start an animation that animates the images frame from its current size towards a maximum size.

Start the animation as soon as you detect the long press gesture.

If the gesture ends, get the current frame size from the presentationLayer of the animated view/image and update the view/image's frame to that size by starting a new animation with UIViewAnimationOptionBeginFromCurrentState so that the old animation will stop.

That should give you a smoothly growing balloon.

Question 3

Try this....

imageView = [[UIImageView alloc] initWithFrame:(CGRectMake(120, 100, 30, 30))];
imageView.backgroundColor = [UIColor redColor];
[self.view addSubview:imageView];

imageView.userInteractionEnabled = TRUE;

UILongPressGestureRecognizer *g = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPress:)];
[g setMinimumPressDuration:0.001];
[imageView addGestureRecognizer:g];

And Add these methods

-(void)longPress:(UITapGestureRecognizer *)t
{
    if (t.state == UIGestureRecognizerStateBegan)
    {
        [timer invalidate];
        timer = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(makeIncrc) userInfo:nil repeats:TRUE];
    }
    else if (t.state == UIGestureRecognizerStateEnded || t.state == UIGestureRecognizerStateCancelled)
    {
        [timer invalidate];
        timer = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(makeDec) userInfo:nil repeats:TRUE];
    }

}

-(void)makeIncrc
{
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:0.5];
    [UIView setAnimationCurve:(UIViewAnimationCurveLinear)];

    CGRect frame = imageView.frame;
    frame.origin.x = frame.origin.x - 5;
    frame.origin.y = frame.origin.y - 5;
    frame.size.width = frame.size.width + 10;
    frame.size.height = frame.size.height + 10;
    imageView.frame = frame;

    [UIView commitAnimations];

}

-(void)makeDec
{
    if (imageView.frame.size.width < 20 || imageView.frame.size.height < 20)
    {
        [timer invalidate];
    }
    else
    {
        [UIView beginAnimations:nil context:nil];
        [UIView setAnimationDuration:0.5];
        [UIView setAnimationCurve:(UIViewAnimationCurveLinear)];


        CGRect frame = imageView.frame;
        frame.origin.x = frame.origin.x + 5;
        frame.origin.y = frame.origin.y + 5;
        frame.size.width = frame.size.width - 10;
        frame.size.height = frame.size.height - 10;
        imageView.frame = frame;

        [UIView commitAnimations];
    }
}

Question 4

Here's a Swift version. I had to replace invalidate() calls with "paused" in order to avoid runaway inflation.

var inflateDisplayLink: CADisplayLink?
var inflateStart: NSDate!
var longPressLocation: CGPoint!
var inflatable: UIImageView!

func handleInflation(inflateGesture: UILongPressGestureRecognizer) {

    longPressLocation = inflateGesture.locationInView(self.view)
    let imageView = inflateGesture.view as! UIImageView

    switch (inflateGesture.state) {
        case .Began:
            println("Long press Began .................")
            inflateStart = NSDate()

            let tempImageView = UIImageView(image: imageView.image)
            tempImageView.contentMode = .ScaleAspectFit
            tempImageView.frame = imageView.frame
            self.view.addSubview(tempImageView)

            inflatable = tempImageView

            if inflateDisplayLink == nil {
                inflateDisplayLink = CADisplayLink(target: self, selector: Selector("inflate"))
                inflateDisplayLink!.frameInterval = 1
                inflateDisplayLink!.addToRunLoop(NSRunLoop.currentRunLoop(), forMode: NSDefaultRunLoopMode)
            } else {
                inflateDisplayLink!.paused = false
            }

            break

        case .Changed:
            println("Long press Changed .................")
            break

        case .Ended:
            println("Long press Ended .................")
            inflateDisplayLink!.paused = true
            break

        default:
            break
    }
}

func inflate() {
    var inflateEnd = NSDate()
    // Convert from Double to CGFloat, due to bug (?) on iPhone5
    var inflateInterval: CGFloat = CGFloat((Double(inflateEnd.timeIntervalSince1970) - Double(inflateStart.timeIntervalSince1970))) * 5.0

    inflatable.frame = CGRectMake(inflatable.frame.origin.x, inflatable.frame.origin.y, inflatable.bounds.size.width + inflateInterval, inflatable.bounds.size.height + inflateInterval)
    inflatable.center = longPressLocation.center

    if inflatable.bounds.size.width > 200  {
        inflateDisplayLink!.paused = true
    }
}