I need to be able to detect immediate touch and get its position. (so didSelectRowAtIndexPath can't help us since it does not act immediately when scrolling up and down fast, you need to breathe in and select one by one)
Already tried everything I can think of. Touches began in each cell does not work because it suddenly behaves like didSelectRowIndexPath when implemented in custom cell class. Same result with TableViewController, the nature of touches began (you touch it, respond right away) just won't work.
* I'm not trying to TAP. Need to be able to get TOUCH (TapGesture does not respond when swiping very carefully/slowly but touches began always does) *
Not sure it's what you need, but you can create a TapGestureRecognizer.
You will likely run into conflicts with the UITableView's own gesture recognisers, but there are mechanisms to solve these which should hopefully let you achieve your desired behaviour (look up requireGestureRecognizerToFail and UIGestureRecognizerDelegate's gestureRecognizerShouldBegin and shouldRecognizeSimultaneouslyWithGestureRecognizer).
Try this.
In cellForIndexpath method.
UITapGestureRecognizer *singleFingerTap =
[[UITapGestureRecognizer alloc] initWithTarget:self
action:#selector(handleSingleTap:)];
singleFingerTap.delegate=self;
cell.contentView.tag=indexPath.row;
[cell.contentView addGestureRecognizer:singleFingerTap];
//The event handling method
- (void)handleSingleTap:(UITapGestureRecognizer *)recognizer {
NSLog(#"%ld",(long)recognizer.view.tag);
}
I think what you need to do, add UILongPressGestureRecognizer to tableview, so normal touch will scroll and long press will do whatever you want to. Set its minimumPressDuration like 0.2 so it won't take much time. Add action for UILongPressGestureRecognizer and in that method get location like:
CGPoint touchPointInView = [sender locationInView: self.view]; //location reespective to view
CGPoint touchPointInView1 = [sender locationInView: tableView]; //location respective to tableview
Related
If you assign a UITapGestureRecognizer to a UIView the UIGestureRecognizerStateBegan doesn't appear when the user has touched the view.
// Tap
_tapGestureRecognizer =
[[UITapGestureRecognizer alloc] initWithTarget:self
action:#selector(tap:)];
[_someView addGestureRecognizer:_tapGestureRecognizer];
Instead the recognizer jumps straight to UIGestureRecognizerStateEnded when the user performs the tap.
I have to change that view to a UIButton and listen to the touchDown method.
_someButton = [[UIButton alloc] init];
[_someButton addTarget:self action:#selector(touchDown:) forControlEvents:UIControlEventTouchDown];
[self addSubview: _someButton];
I don't like changing the UIView to a UIButton just for this.
Can I use the UITapGestureRecognizer instead?
Let me start by saying that UITapGestureRecognizer docs clearly tell to expect a callback for all states.
For gesture recognition, the specified number of fingers must tap the view a specified number of times. Although taps are discrete gestures, they are discrete for each state of the gesture recognizer. The system sends the associated action message when the gesture begins and then again for each intermediate state until (and including) the ending state of the gesture. Code that handles tap gestures should test for the state of the gesture, for example:
func handleTap(sender: UITapGestureRecognizer) {
if sender.state == .ended {
// handling code
}
}
Hower it makes little to no sense (specially in case of single tap recognizer). You touched a view (that had the tap gesture added to it), you haven't yet lifted your finger, moved it etc. System can't know at the time of .touchDown event that this interaction is going to turn into a successful recognition of a tap (which requires lifting the finger up).
Essentially UITapGestureRecognizer (for a single touch tap) is a .touchDown + .touchUp combination. If anything else happens after .touchDown like a drag (.touchDragInside OR .touchDragExit), it may lead to successful recognition of a pan gesture (tableView scrolling etc.)
You can think of UITapGestureRecognizer roughly equivalent to .touchUpInside event for a button. A .touchUpInside event for a button doesn't call your function for .touchDown event, It is only possible to receive that event by explicitly asking for the same.
Why do the docs say so?
Maybe system is able to identify the .began state for other scenarios
a multi-tap gesture - double/triple tap (see UITapGestureReconizer.numberOfTapsRequired)
a multi-touch tap - 2/3 finger tap (see UITapGestureReconizer.numberOfTouchesRequired)
You have to test other scenarios for this if you want to know more.
Is there any way to get UITapGestureRecognizer to run on touch began?
I can't use touchesBegan because I am using a UITableView and the super view steals the event essentially.
I just want to detect when the screen is first touched. Why is this so difficult? Maybe I need a different solution than using tapgesturerecognizer?
You can use state property of UIGestureRecognizer to identify various states of any gesture -
#property(nonatomic,readonly) UIGestureRecognizerState state; // the current state of the gesture recognizer
So when the gesture begin, use something like this in your registered handler method -
if (gestureRecognizer.state == UIGestureRecognizerStateBegan) {
// Do your stuff
}
You can add a tap gesture recognizer to the tableView in viewDidLoad like this:
UITapGestureRecognizer *tapGestureRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(tapGestureRecognized:)];
[self.tableView addGestureRecognizer:tapGestureRecognizer];
Then implement this method:
- (void)tapGestureRecognized:(UITapGestureRecognizer *)tapGestureRecognizer {
NSLog(#"tap gesture recognized");
}
Just tested this out, and works fine. For every tap i get the log message on my console. Note that this prevents the tableview from receiving the taps, other gestures will just be handled by the table view as usual.
You need to set delaysContentTouches = NO
I would like to detect the (initial) touch position in my UIScrollView when the user starts dragging. I have googled this issue and many seem to struggle with this very issue. Now, while I still can't wrap my head around why Apple would not let users access touch information in a scroll view, I can't help but find a solution by myself. However all my tries failed, so I would like to ask you.
Here is what I thought would work:
I set up a UIPanGestureRecognizer like this in my UIScrollView subclass and add it to its gesture recognizers:
UIPanGestureRecognizer *tapDrag = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(touchedAndDragged:)];
tapDrag.cancelsTouchesInView = NO;
tapDrag.delegate = self;
[self addGestureRecognizer:tapDrag];
And the corresponding method:
-(void)touchedAndDragged:(UIPanGestureRecognizer*)t{
CGPoint loc = [t locationInView:self];
//do something with location (that is exactly what I need)
//...
//Now DISABLE and forward touches to scroll view, so that it scrolls normally
t.enabled = NO;
/****
?????
*****/
}
As indicated by the comments, I would like to disable the pan gesture after I have the point and then disable the recognizer(while STILL dragging!) and "pass" the touches to my scroll view, so that the user can scroll normally. Is that feasible at all? Is there any other solution to it ?
Well UIScrollView's already have a built in pan gesture that you could tap into. Usage would be as simple as setting your class as your scroll view's delegate (to utilize scrollViewWillBeginDragging) and using UIPanGestureRecognizer's -locationInView: to determine touch location.
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
CGPoint location = [scrollView.panGestureRecognizer locationInView:scrollView];
NSLog(#"%#",NSStringFromCGPoint(location));
}
Why don't you grab the start location in -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event that will be more convenient and efficient.
I'd like to code my own tap gesture recognizer, to detect the number of taps and number of touches (I don't want to use the iOS tap gesture recognizer because I want to extend it later in various other manners) ;
I tried the following : use the first motionBegin number of touches as the numberOfTouches of the tap, increment the numberOfTaps, and start the tap detection timer to detect the tap gesture if no new taps has been seen in a while
The problem is that one quickly realises that when doing a double-touch tap gesture, iOS either correctly detects one motionBegin with a double touch, or two quick one touch events. I guess a correct implementation should try to detect those quick one touch events that happen closely, but I'm wondering if there is a better way to implement the gesture recognizer.
Someone knows how the iOS tap gesture is implemented?
1. Add UIGestureRecognizerDelegate in your .h file. like
#interface finalScreenViewController : UIViewController <UIGestureRecognizerDelegate>
{
// do your stuff
}
2. Create a view in your viewDidLoad method (or any other method) you wanna to add the gesture in your .m file
ex
UIView * myView=[[UIView alloc]init];
myView.frame=CGRectMake(0,0.self.view.frame.size.width,self.view.frame.size.height);
[self.view addSubView: myView];
UITapGestureRecognizer *letterTapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(tapMethod:)];
letterTapRecognizer.numberOfTapsRequired = 1;
[myView addGestureRecognizer:letterTapRecognizer];
3. you can get view by
- (void) tapMethod:(UITapGestureRecognizer*)sender {
UIView *view = sender.view;
NSLog(#"%d", view.tag);//By tag, you can find out where you had tapped.
}
First off this question has been helpful in my understanding of how to subclass UIButton for long presses. I would like to do the same for UISegmentedControl, however I don't see how I would be able to identify which segment was held down since UISegmentedControl does allow direct access to it's segments (UISegmentedControl.h shows them as private). I could just customize a few UIButtons to look like an UISegmentedControl however I would also have to implement the momentary switch logic. Which wouldn't be a big deal but subclassing UISegmentedControl seems cleaner to me.
BTW, I'm using this control to imitate a radio's preset controls: tap to go to a saved station and hold to assign the current station to that segment.
I tried this without subclassing and it seems to work.
UILongPressGestureRecognizer* recognizer = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:#selector(pressGesture:)];
recognizer.delegate = self;
[mySegCtrl addGestureRecognizer:recognizer];
[recognizer release];
...
-(void)pressGesture:(UILongPressGestureRecognizer*)gesture
{
NSLog(#"pressGesture %#", gesture);
}
Long press first selects the segment then fires the gesture. If you aren't getting the callback check my code - I got stuck for a while because I wasn't setting recognizer.delegate=self.