tap gesture recognizer - which object was tapped?

Question

I'm new to gesture recognizers so maybe this question sounds silly: I'm assigning tap gesture recognizers to a bunch of UIViews. In the method is it possible to find out which of them was tapped somehow or do I need to find it out using the point that was tapped on screen?

for (NSUInteger i=0; i<42; i++) {
        float xMultiplier=(i)%6;
        float yMultiplier= (i)/6;
        float xPos=xMultiplier*imageWidth;
        float yPos=1+UA_TOP_WHITE+UA_TOP_BAR_HEIGHT+yMultiplier*imageHeight;
        UIView *greyRect=[[UIView alloc]initWithFrame:CGRectMake(xPos, yPos, imageWidth, imageHeight)];
        [greyRect setBackgroundColor:UA_NAV_CTRL_COLOR];

        greyRect.layer.borderColor=[UA_NAV_BAR_COLOR CGColor];
        greyRect.layer.borderWidth=1.0f;
        greyRect.userInteractionEnabled=YES;
        [greyGridArray addObject:greyRect];
        [self.view addSubview:greyRect];
        NSLog(@"greyGrid: %i: %@", i, greyRect);

        //make them touchable
        UITapGestureRecognizer *letterTapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(highlightLetter)];
        letterTapRecognizer.numberOfTapsRequired = 1;
        [greyRect addGestureRecognizer:letterTapRecognizer];
    }

Answer 1

You should amend creation of the gesture recogniser to accept parameter (add colon ':')

UITapGestureRecognizer *letterTapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(highlightLetter:)];

And in your method highlightLetter: you can access the view attached to recogniser:

-(IBAction) highlightLetter:(UITapGestureRecognizer*)recognizer
{
    UIView *view = [recognizer view];
}

Answer 2

Typical 2019 example

Say you have a FaceView which is some sort of image. You're going to have many of them on screen (or, in a collection view, table, stack view or other list).

In the class FaceView you will need a variable "index"

class FaceView: UIView {
   var index: Int

so that each FaceView can be self-aware of "which" face it is on screen.

So you must add var index: Int to the class in question.

So you are adding many FaceView to your screen ...

let f = FaceView()
f.index = 73
.. you add f to your stack view, screen, or whatever.

You now add a click to f

f.addGestureRecognizer(UITapGestureRecognizer(target: self,
                           action: #selector(tapOneOfTheFaces)))

Here's the secret:

@objc func tapOneOfTheFaces(_ sender: UITapGestureRecognizer) {
    if let tapped = sender.view as? CirclePerson {
        print("we got it: \(tapped.index)")

You now know "which" face was clicked in your table, screen, stack view or whatever.

It's that easy.

Answer 3

you can use

 - (void)highlightLetter:(UITapGestureRecognizer*)sender {
     UIView *view = sender.view; 
     NSLog(@"%d", view.tag); 
}

view will be the Object in which the tap gesture was recognised

Answer 4

Use this code in Swift

func tappGeastureAction(sender: AnyObject) {
    if let tap = sender as? UITapGestureRecognizer {
        let point = tap.locationInView(locatedView)
        if filterView.pointInside(point, withEvent: nil) == true {
            // write your stuff here                
        }
    }
}

Answer 5

in swift it quite simple

Write this code in ViewDidLoad() function

let tap = UITapGestureRecognizer(target: self, action: #selector(tapHandler(gesture:)))
    tap.numberOfTapsRequired = 2
    tapView.addGestureRecognizer(tap)

The Handler Part this could be in viewDidLoad or outside the viewDidLoad, batter is put in extension

@objc func tapHandler(gesture: UITapGestureRecognizer) {
    currentGestureStates.text = "Double Tap"
} 

here i'm just testing the code by printing the output if you want to make an action you can do whatever you want or more practise and read

Answer 6

Here is an update for Swift 3 and an addition to Mani's answer. I would suggest using sender.view in combination with tagging UIViews (or other elements, depending on what you are trying to track) for a somewhat more "advanced" approach.

1. Adding the UITapGestureRecognizer to e.g. an UIButton (you can add this to UIViews etc. as well) Or a whole bunch of items in an array with a for-loop and a second array for the tap gestures.

    let yourTapEvent = UITapGestureRecognizer(target: self, action: #selector(yourController.yourFunction)) 
    yourObject.addGestureRecognizer(yourTapEvent) // adding the gesture to your object

2. Defining the function in the same testController (that's the name of your View Controller). We are going to use tags here - tags are Int IDs, which you can add to your UIView with yourButton.tag = 1. If you have a dynamic list of elements like an array you can make a for-loop, which iterates through your array and adds a tag, which increases incrementally

   func yourFunction(_ sender: AnyObject) {
       let yourTag = sender.view!.tag // this is the tag of your gesture's object
       // do whatever you want from here :) e.g. if you have an array of buttons instead of just 1:
       for button in buttonsArray {
         if(button.tag == yourTag) {
           // do something with your button
         }
       }
   }
   

The reason for all of this is because you cannot pass further arguments for yourFunction when using it in conjunction with #selector.

If you have an even more complex UI structure and you want to get the parent's tag of the item attached to your tap gesture you can use let yourAdvancedTag = sender.view!.superview?.tag e.g. getting the UIView's tag of a pressed button inside that UIView; can be useful for thumbnail+button lists etc.