UIPanGestureRecognizer stop calling the selector - ios

Question

I'm having trouble to work with UIPanGestureRecognizer as it just calls the selector when I have my finger moving, I want it to keep calling the selector even my finger is standing at the same place.
There are 4 objects on the screen one at the top, one at the right side, one at the left side and one at the bottom. I have an object at the center of the screen (this is the one I'm moving with the panGesture). When this object touches the others I want it to give me a Log, it works when it touches but if I keep my finger at the same place it stops to give me logs, if I move a little it starts to give me logs again.
Is there anyway I can keep calling the selector even with my finger at the same place?
here is a code example:
- (void)moveObject:(UIPanGestureRecognizer *)sender
{
CGPoint translation = [sender translationInView:self.limiteDirecional];
[sender setTranslation:CGPointMake(0, 0) inView:self.limiteDirecional];
CGPoint center = sender.view.center;
center.y += translation.y;
int yMin = 0;
int yMax = self.limiteDirecional.frame.size.height;
if (center.y < yMin || center.y > yMax )
return;
sender.view.center = center;
center.x += translation.x;
int xMin = self.limiteDirecional.frame.size.width;
int xMax = 0;
if (center.x > xMin || center.x < xMax)
return;
sender.view.center = center;
if (CGRectIntersectsRect(sender.view.frame,self.Top.frame)) {
NSLog(#"TOP");
}
if (CGRectIntersectsRect(sender.view.frame,self.Botton.frame)) {
NSLog(#"BOTTON");
}
if (CGRectIntersectsRect(sender.view.frame,self.Right.frame)) {
NSLog(#"RIGHT");
}
if (CGRectIntersectsRect(sender.view.frame,self.Left.frame)) {
NSLog(#" LEFT");
}
if (sender.state == UIGestureRecognizerStateEnded) {
sender.view.center = CGPointMake(self.view.frame.size.width / 2, self.view.frame.size.height / 2);
}
}

Answer 1

I'm not entirely following the logic of your routine, so I'll provide a generic template of what a solution might look like when you want continuous events in the middle of a gesture, whether the user is moving their finger or not. Hopefully you can adapt this technique for your own purposes.
This uses CADisplayLink, which is considered a better technique for animation than the older technique of using a NSTimer. To use CADisplayLink, though, you need to add the needed framework, QuartzCore.framework, to your project, if you haven't already. Also note that in my gesture recognizer, I'm checking the state of a gesture, to know whether we're starting a gesture, in the middle of one, or ending one:
#import "ViewController.h"
#import <QuartzCore/QuartzCore.h>
#interface ViewController ()
#property (nonatomic, strong) CADisplayLink *displayLink;
#property (nonatomic) CGPoint translationInView;
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
UIPanGestureRecognizer *gesture = [[UIPanGestureRecognizer alloc] initWithTarget:self
action:#selector(handleGesture:)];
// I'm adding to the main view, but add it to whatever you want
[self.view addGestureRecognizer:gesture];
}
- (void)startDisplayLink
{
self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:#selector(handleDisplayLink:)];
[self.displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
}
- (void)stopDisplayLink
{
[self.displayLink invalidate];
self.displayLink = nil;
}
- (void)handleDisplayLink:(CADisplayLink *)displayLink
{
NSLog(#"%s translationInView = %#", __FUNCTION__, NSStringFromCGPoint(self.translationInView));
// Do here whatever you need to happen continuously while the user is in the
// middle of the gesture, whether their finger is moving or not.
}
- (void)handleGesture:(UIPanGestureRecognizer *)gesture
{
self.translationInView = [gesture translationInView:gesture.view];
if (gesture.state == UIGestureRecognizerStateBegan)
{
[self startDisplayLink];
// Do whatever other initialization stuff as the user starts the gesture
// (e.g. you might alter the appearance of the joystick to provide some
// visual feedback that they're controlling the joystick).
}
else if (gesture.state == UIGestureRecognizerStateChanged)
{
// Do here only that stuff that actually changes as the user is moving their
// finger in the middle of the gesture, but which you don't need to have
// repeatedly done while the user's finger is not moving (e.g. maybe the
// visual movement of the "joystick" control on the screen).
}
else if (gesture.state == UIGestureRecognizerStateEnded ||
gesture.state == UIGestureRecognizerStateCancelled ||
gesture.state == UIGestureRecognizerStateFailed)
{
[self stopDisplayLink];
// Do whatever other cleanup you want to do when the user stops the gesture
// (e.g. maybe animating the moving of the joystick back to the center).
}
}
#end
You can achieve a similar effect if you use NSTimer, too. Whatever works better for you.