I have the following code in a viewDidLoad on a UIViewController:
UIScreenEdgePanGestureRecognizer *edgeRecognizer = [[UIScreenEdgePanGestureRecognizer alloc] initWithTarget:self action:#selector(handleRightEdgeSwipe:)];
edgeRecognizer.edges = UIRectEdgeRight;
[self.view addGestureRecognizer:edgeRecognizer];
and the purposes is to trigger a view to slide in when a right edge gesture is detected.
-(void)handleRightEdgeSwipe:(UIGestureRecognizer*)sender
{
NSLog(#"Showing Side Bar");
[self presentPanelViewController:_lightPanelViewController withDirection:MCPanelAnimationDirectionRight];
}
But I am seeing that the "handleRightEdgeSwipe" function is triggered multiple times - sometimes 5 times which makes the side bar view that should smoothly animate slide in to flash multiple times.
(NOTE: I tried triggering the view to appear from a UIButton and it works fine).
Why is the right edge gesture triggered multiple times and how can I fix it?
As noted, the UIScreenEdgePanGestureRecognizer invokes your action multiple times as the state of the GestureRecognizer changes. See the documentation for the state property of the UIGestureRecognizer class. So, in your case I believe the answer you're looking for is to check if the state is "ended". Thus:
-(void)handleRightEdgeSwipe:(UIGestureRecognizer*)sender
{
if (sender.state == UIGestureRecognizerStateEnded)
{
NSLog(#"Showing Side Bar");
[self presentPanelViewController:_lightPanelViewController withDirection:MCPanelAnimationDirectionRight];
}
}
This gesture is not a single-shot event but continuous.
handleRightEdgeSwipe: is called once whenever sender.state changes or the touch moved around. You have to move the UIButton depending on the gesture's state and locationInView:.
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 have a 2d map that the user can zoom and pan using the gesture recognizers. While it works, i want the user to start panning immediately after a zoom once they have 1 finger lifted. Unfortunately, in the docs it says:
The gesture ends (UIGestureRecognizerStateEnded) when both fingers
lift from the view.
which is pretending me from going from a pinch zoom to a pan right away. What could i do to fix this?
This is possible, and easy! It involves being your gesture recognizer's delegate. Something no-one seems to know exists. In my view controller subclass I have declared both conforming to the protocol <UIGestureRecognizerDelegate> and two ivars:
UIPinchGestureRecognizer *myPinchGR;
UIPanGestureRecognizer *myPanGR;
These ivars are instantiated in view did load. Notice setting self as the delegate.
-(void)viewDidLoad{
[super viewDidLoad];
myPanGR = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(panTarget:)];
myPanGR.delegate = self;
[self.view addGestureRecognizer:myPanGR];
myPinchGR = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:#selector(pinchTarget:)];
myPinchGR.delegate = self;
[self.view addGestureRecognizer:myPinchGR];
}
One of the delegate calls made by a UIGestureRecognizer is shouldRecognizeSimultaneouslyWithGestureRecognizer: if I had more than two gesture recognizers then this function would have to contain some logic. But since there are only two I can just return YES.
-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer{
return YES;
}
Now you do have to include a little (very little) extra logic in your action methods to screen for the appropriate conditions.
-(void)panTarget:(UIPanGestureRecognizer *)panGR{
if (panGR.numberOfTouches > 1) return;
NSLog(#"panny");
}
-(void)pinchTarget:(UIPinchGestureRecognizer *)pinchGR{
if (pinchGR.numberOfTouches < 2) return;
NSLog(#"pinchy");
}
Run this code an look at the logs. you will see when you move one finger you will see "panny" when you place a second finger down you will see "pinchy", and back and forth.
Use this code inside the gesture handling method.
if (gesture.numberOfTouches != 2) {
// code here to end pinching
}
As Gesture handling method will be called immediately when user lift a finger while 2 finger pinching.
I have written a UIScrollView subclass that I am using to scroll a series of UITableViews. See the following diagram:
As you can see I have several vertically scrolling UITableViews, that are being scrolled horizontally inside a parent UIScrollView. This all works fine. However the application has a number of global gestures. For example, if I swipe in a given direction with 2 fingers, I do a UIView transition to another part of the app. but if I do the gesture on top of the scroll view and/or its child table views, they naturally scroll their content. This doesn't look good and causes some layout issues.
What I would like to figure out is how to disable all scrolling, on both the UIScrollView and its child UITableViews, when a user touches anywhere with two fingers, and only with two fingers. I've tried variations of overriding touchesBegan, touchesEnded, touchesShouldCancel etc... but I can't get it quite right. Any help is much appreciated.
Here is my gesture handling code:
UISwipeGestureRecognizer *twoFingerSwipeUp = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:#selector(handleTwoFingerSwipe:)];
[twoFingerSwipeUp setNumberOfTouchesRequired:2];
[twoFingerSwipeUp setDirection:UISwipeGestureRecognizerDirectionUp];
[twoFingerSwipeUp setDelegate:self];
// 'self' is the superview of the UIScrollView, which is a UIView.
[self addGestureRecognizer:twoFingerSwipeUp];
[twoFingerSwipeUp release];
// ... repeat the above code for up, down, left, right gestures ...
- (void)handleTwoFingerSwipe:(UISwipeGestureRecognizer*)swipeGesture {
switch ([swipeGesture direction]) {
case UISwipeGestureRecognizerDirectionUp:
[self changeToView:viewAbove];
break;
case UISwipeGestureRecognizerDirectionDown:
[self changeToView:viewBelow];
break;
case UISwipeGestureRecognizerDirectionRight:
[self changeToView:viewToTheRight];
break;
case UISwipeGestureRecognizerDirectionLeft:
[self changeToView:viewToTheLeft];
break;
}
}
Try setting panGestureRecognizer.maximumNumberOfTouches = 1 on all scroll and table views (iOS 5 only).
If you're using a swipe recogniser for the two-finger swipe, require the recognisers of the scroll view (including the table views — they're scroll view as well) to fail when the two-finger recogniser recognises its gesture.
[[scrollView panGestureRecognizer] requireGestureRecognizerToFail: twoFingerRecogniser];
Iterate the above code for every scroll view and table view.
(P.S.: "recogniser" is British English, not a spelling err.)
Hope that helps. :-)
Write this code:
scrollView.minimumZoomScale=1.0;scrollView.maximumZoomScale=1.0;
scrollView.delegate self];
And Here is scrollViewDelegate Method:-
-(UIView*)viewForZoomingInScrollView:(UIScrollView *)aScrollView{
return aScrollView;}
One thing that you should be doing is to check that the gesture has finished before acting upon it:
if (swipeGesture.state == UIGestureRecognizerStateEnded) {
// Do your think
}
I've known odd things to happen otherwise.
Just disable user interaction in the parent scroll view. You need a UIWindow subclass and override -sendEvent: method because this gets called BEFORE any gesture recognizer. There, if you detect two touches, send a notification. Let the scroll view listen to it and disable user interaction if it occurs. And if touches ended, let it re-enable user interaction.
I am hoping someone will be able to help me with a problem that is doing my head in at the moment!
Given the following view hierarchy
I want to be able to detect swipe gestures on my custom UITableViewCell.
I have subclassed the UIScrollView and have a hitTest:withEvent: method that checks whether I am touching the tableview cell (or its content) or not, in which case I set the following scroll view properties:
- (UIView*)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
UIView* result = [super hitTest:point withEvent:event];
if ([result.superview isKindOfClass:[UITableViewCell class]] || [result.superview tag] == SUBVIEW_TAG)
{
self.canCancelContentTouches = NO;
self.delaysContentTouches = YES;
} else {
self.canCancelContentTouches = YES;
self.delaysContentTouches = NO;
}
return result;
}
I have also implemented:
- (BOOL)touchesShouldCancelInContentView:(UIView *)view
{
if (view.tag == SUBVIEW_TAG || [[view superview] isKindOfClass:[UITableViewCell class]])
return NO;
return YES;
}
And am returning NO in case the view being touched is the table view cell.
These methods are all getting called and performing their actions as expected, but I am still unable to stop the UIScrollView from "hogging" the swipe gesture.
The interesting thing is that if I include the UIView that contains the tableview and cell on both of the methods above (the one with SUBVIEW_TAG) it works perfectly so I am guessing it must be something to do with the fact that UITableView inherits from UIScrollView.
My main goal is to be able to swipe on the cell to reveal more options for the cell. A horizontal swipe anywhere else on that view would be captured by the scroll view and shift the content horizontally as per its normal behaviour.
Any ideas would be very much appreciated!
Thanks!
Rog
I had a similar problem with a swipe detect for a component inside a scrollview and I was able to resolve it with
[scrollView.panGestureRecognizer requireGestureRecognizerToFail:swipeGesture]
Where scrollView is the scroll view object that acts like container and swipeGesture is the component swipe gesture object inside scrollview.
So, you can define a swipe for the cell object like this (for right swipe in the example, custom it as you want)
UISwipeGestureRecognizer* rightSwipeRecognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:#selector(yourMethod)];
[rightSwipeRecognizer setDirection:UISwipeGestureRecognizerDirectionLeft];
[cell addGestureRecognizer:rightSwipeRecognizer];
and then do
[scrollView.panGestureRecognizer requireGestureRecognizerToFail:rightSwipeRecognizer]
The documentation of requireGestureRecognizerToFail says:
This method creates a relationship with another gesture recognizer
that delays the receiver’s transition out of
UIGestureRecognizerStatePossible. The state that the receiver
transitions to depends on what happens with otherGestureRecognizer:
If otherGestureRecognizer transitions to
UIGestureRecognizerStateFailed, the receiver transitions to its normal
next state.
if otherGestureRecognizer transitions to
UIGestureRecognizerStateRecognized or UIGestureRecognizerStateBegan,
the receiver transitions to UIGestureRecognizerStateFailed.
An example where this method might be called is when you want a
single-tap gesture require that a double-tap gesture fail.
Availability Available in iOS 3.2 and later.
Hope helps!
The solution is pretty simple. All you need to do is add UIScrollView inside you UITableViewCell. It will prevent "hogging" effect during swipe gesture.