Question

Im working on an app with zooming function.
In this app I have this button. I want it to respond to tapping in several ways:

Single tap: Zoom in slightly.

Double tap: Zoom in to the max.

Ive tried several options to achieve this but none are what I want.

UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTapGesture:)];
tapGesture.numberOfTapsRequired = 2;
[self.view addGestureRecognizer:tapGesture];

---

[zoomin addTarget:self action:@selector(zoominMax) forControlEvents:UIControlEventTouchDownRepeat];

Both work on single and double tap but when I press the button once to slightly zoom and seconds later I press it again it doesn’t zoom in slightly, it zooms in to the max.

It is possible to fix this with a timer and location check so that when u tap and tap again u can be sure that the location is in a similar area and the taps happened within timer range.

But is this what I really need?
Is there a simpler solution?

Answer 1

You can do it with two gesture recognizers and a timer:

UITapGestureRecognizer *tapGestureRecognizer = [[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tap:)] autorelease];
[myView addGestureRecognizer:tapGestureRecognizer];

UITapGestureRecognizer *doubleTapGestureRecognizer = [[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(doubleTap:)] autorelease];
doubleTapGestureRecognizer.numberOfTapsRequired = 2;
[myView addGestureRecognizer:doubleTapGestureRecognizer];

You’ll have to use a slight delay in your tap: action before zooming in slightly because the first tap could be followed by a second tap:

- (void)tap:(UITapGestureRecognizer *)recognizer
{
    [self performSelector:@selector(singleTap) withObject:nil afterDelay:0.25];
}

- (void)singleTap
{
    //slightly zoom in...
}

- (void)doubleTap:(UITapGestureRecognizer *)recognizer
{
    //Cancel the timer for the single tap action:
    [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(singleTap) object:nil];
    //zoom in to the max zoom level...
}