Fernando Fernando - 1 month ago 17
iOS Question

filtering single and double taps

When the user single taps my view, i need one specific method to run.
When the user double taps, i need another method do take place.

The problem is that the double tap triggers the single tap, and it introduce bugs in my logic.
I can't use UIGestureRecognizer because i need to keep track of the points.

I try some booleans, but no chance. I also tried the cancel/perfomSelector-delay technique, but it does not work (that's strange because other folks on other forums said it works, maybe the simulator touch detection is different ?)

I'm trying to let the user set the position (drag, rotate) of a board piece, but i need to be aware of piece intersections, clip to the board area, etc, that's why a simple boolean will not solve the problem.

Thanks in advance!

Answer

Check this, seems right what you are looking for:

Below the code to use UITapGestureRecognizer to handle single tap and double tap. The code is designed that it won't fire single tap event if we got double tap event. The trick is use requireGestureRecognizerToFail to ask the single tap gesture wait for double tap event failed before it fire. So when the user tap on the screen, the single tap gesture recognizer will not fire the event until the double tap gesture recognizer. If the double tap gesture recognizer recognize the event, it will fire a double tab event and skip the single tap event, otherwise it will fire a single tap event.

    UITapGestureRecognizer *doubleTapGestureRecognizer = [[UITapGestureRecognizer alloc]
                            initWithTarget:self action:@selector(handleDoubleTap:)];
    doubleTapGestureRecognizer.numberOfTapsRequired = 2;

    //tapGestureRecognizer.delegate = self;
    [self addGestureRecognizer:doubleTapGestureRecognizer];

    //
    UITapGestureRecognizer *singleTapGestureRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleSingleTap:)];
    singleTapGestureRecognizer.numberOfTapsRequired = 1;

    [singleTapGestureRecognizer requireGestureRecognizerToFail: doubleTapGestureRecognizer];
    //tapGestureRecognizer.delegate = self;
    [self addGestureRecognizer:singleTapGestureRecognizer];

Possibly I don't understand exactly what you mean by "i need to keep track of the points", but I don't see any problems with doing this with a gesture recognizer.