Right now I'm using:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
NSLog(#"Function called");
}
which activates on press down, which is correct. But, I also want to continue calling the function, let's say every second, as long as the finger is still on the screen (in other words: until the finger is lifted up).
How would I go about doing this?
Related
I'm developing an app for iOS, and I want the user to be able to select some stuff on the screen, and then at the end of the selection be able to hold the finger for a second, to trigger some other event.
I have already created a lot of actions, for when the user marks stuff by swiping around. For this i have been using:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
//Stuff here
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
//Stuff here
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
//Stuff here
}
I don't care if these functions are used, or if it done by UIGestureRecognizer, but i simply can't find a efficient and simple way to implement this.
Any suggestions?
You could initiate a NSTimer when a touch began, if the finger is within a target area, and if the touch ended function is called before the timer has fired r some condition is met within the touch moved function then cancel the timer, otherwise let it fire.
You'll probably need to use a timer as well as a pan gesture recognizer. When the finger reaches a target area, start the timer. If the finger moves out of the area, invalidate the timer. If the timer fires, it's a long press.
I am trying to achieve a certain behavior in which an object executes a method when a tap passes into the bounds of the object, and then another when the tap leaves its bounds. Since this is a difficult scenario to put into words, I drew a picture:
Which type of ControlEvent is this, and if it doesn't exist, are there other accepted methods of getting this to work?
Thanks,
James
There isnt any control event for this that i know of. You will have to implement this yourself. On the view controller (superview to your button) place the following methods, something like this:
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
// Touches began, check the position of my touch. Is it outside a button?
// note that in a BOOL
...
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
// was my first touch on a button? if not, see if my current touch is inside
// the button, note that
...
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
// Touch is ending, is my touch outside the button and did i cross through earlier?
// If so, "drag through" event is successful
...
}
hope this helps
My problem is as follows:
I'm displaying a message view with an attachment, in a standard view controller. When the user presses and holds the attachment icon it show the image on screen, when the user lets go the image disappears. This is to aid detecting screenshots while the user is viewing the image.
I use a long press gesture recognizer to detect the touch and then touchesEnded or touchesCancelled to detect the release of the touch.
My problem occurs when the user presses the screen with a second finger, as the release of the second touch is not reported. The code is below, the methods get called in this order:
First long press -> attachmentLongPressed called
Second long press -> attachmentLongPressed called
Release first finger -> touchesEnded called
Release second finger -> nothing called
-(void)attachmentImageLongPressed:(UIImageView *)sender{
if(!self.isAttachmentOpen){
[self setAttachmentOpen:YES];
// Show image...
}
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{
[self setAttachmentOpen:NO];
// Remove image from view
}
-(void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
if(self.isAttachmentOpen){
[self screenshotDetected];
}
}
The result is that the image view is left on screen with no way to dismiss it. Anybody have any suggestions?
I think it should be called touchesEnded when release the second finger. You can log all the touches from all callback to find out which method is being called,
However, it's possible that long pressed gesture might delays the touch ended event, so try to set delaysTouchesEnded to FALSE.
gestureLongPressed.delaysTouchesEnded = FALSE
I'm having an issue with handling more than one touch through the touchesBegan/Moved/Ended methods of UIViewController. I'm also seeing the same behaviour in a cocos2d app (using ccTouchesBegan/Moved/Ended) so I think this question can be applied to all touch handling in iOS. I've put the code that I'm using below, followed by the results that I'm seeing.
All methods are implemented on a UIViewController subclass.
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
NSLog(#"Touches Began");
[self logTouchesFor: event];
[super touchesEnded: touches withEvent: event];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
NSLog(#"Touches Moved");
[self logTouchesFor: event];
[super touchesEnded: touches withEvent: event];
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
NSLog(#"Touches Ended");
[self logTouchesFor: event];
[super touchesEnded: touches withEvent: event];
}
-(void)logTouchesFor:(UIEvent *)event
{
int count = 1;
for (UITouch *touch in event.allTouches)
{
CGPoint location = [touch locationInView: self.view];
NSLog(#"%d: (%.0f, %.0f)", count, location.x, location.y);
count++;
}
}
Now for the interesting results...
Single Touches Work as Expected
Let's say I touch the screen with my thumb. I see in the output window that touchesBegan has been called as expected. I move my thumb around and touchesMoved gets called. Then I lift my thumb off the screen and touchesEnded gets called. All this is as expected, I'm including it in the question as a control case - just to be clear that my view controller is receiving touch events and I haven't missed a vc.view.userInteractionEnabled = YES anywhere.
The Second Touch Doesn't Cause touchesBegan, touchesMoved or touchesEnded to be called
This is the most interesting one. Let's say I touch the screen with my thumb (touchesBegan is called) and hold it still on the screen. Then I touch somewhere else on the screen with my index finger, whilst keeping my thumb in the same place. TouchesBegan is not called. Then let's say I move my index finger whilst keeping my thumb absolutely still (this can be tricky but it is possible). TouchesMoved is not called. Then, I lift my index finger off the screen. TouchesEnded is not called. Finally, I move my thumb and touchesMoved is called. Then I lift my thumb from the screen and touchesEnded is called.
Just to be clear: I've set self.view.multipleTouchEnabled = YES in my viewDidLoad method.
Information About the Second Touch is Available, Providing the First Touch Moves
This time I do something very similar to the example immediately above. I touch the screen with my thumb, then index finger whilst keeping my thumb still. TouchesBegan is called when my thumb hits the screen, but not my index finger. Now I move my thumb, and touchesMoved is called. Not only that, but there are two touches in the event.allTouches array (and yes, the second touch is where I would expect it to be). This means that the system is aware that I have touched the screen a second time, but I am not being notified through the touch handling methods on my view controller.
How Can I be Notified About Changes to the Second Touch?
I'd really like to be able to respond to changes in the location or state of the second touch as they happen, rather than when the first touch also changes. A lot of the time this won't be an issue because it's very hard to change one touch without impacting on the other, but I have at least one situation where it can be an issue. Am I missing something obvious? Has anyone else noticed this behaviour or had issues with it?
In case it's relevant, I'm using an iPhone 3GS running iOS 5.1.
Ok, I started painstakingly rebuilding my project, adding in the files one at a time, and I think I've got it...
There was a subview of the view in question which had userInteractionEnabled == YES. Once I set this to NO, my view controller started getting touchesBegan/Moved/Ended calls for each touch. Presumably, the second touch was being claimed by the subview and not making it to my view controller, but I have no idea why this would only happen with the second touch and not the first.
I haven't figured out what's going on with the cocos2d project yet, but presumably it's a different issue as there are no subviews or nodes that could be doing the same thing.
In UITapGestureRecognizer, when user tap in & then out do we get two different events for this?
I have put UITapUITapGestureRecognizer on one of my view & then when user tap in I need to change the color of the view & when user tap out (i.e. remove his finger from the point) the color should be changed back to original color. I am able to change the color on tap in but not on tap out.
Any advise?
You shouldn't (can't?) use gesture recognizers for that, since they are built to handle raw touch events and parse them into gestures. The "tap in" event isn't a gesture by itself though.
Use these :
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event