How do I use two actions in a UIPanGestureRecognizer? - objective-c

Question

I am working with two subviews. Each will be unique and have it's own "action".
Subview 1 = User can drag around the view, rotate, and zoom it
Subview 2 = When user moves finger across their screen an image is added at each point their finger touches.
I have both of these completed by using UIPanGestureRecognizer. My question is, how can I separate these two actions? I want to be able to add one subview, do what is required, and then when I add the other subview, prevent the previous actions from occurring.
Here is what I have tried, this is done in my panGesture method:
for (UIView * subview in imageView.subviews)
{
if ([subview isKindOfClass:[UIImageView class]])
{
if (subview == _aImageView)
{
CGPoint translation = [panRecognizer translationInView:self.view];
CGPoint imageViewPosition = _aImageView.center;
imageViewPosition.x += translation.x;
imageViewPosition.y += translation.y;
_aImageView.center = imageViewPosition;
[panRecognizer setTranslation:CGPointZero inView:self.view];
}
else if (subview == _bImageView)
{
currentTouch = [panRecognizer locationInView:self.view];
CGFloat distance = [self distanceFromPoint:currentTouch ToPoint:prev_touchPoint];
accumulatedDistance += distance;
CGFloat fixedDistance = 60;
if ([self distanceFromPoint:currentTouch ToPoint:prev_touchPoint] > fixedDistance)
{
[self addbImage];
prev_touchPoint = currentTouch;
}
}
}
}

Answer 1

If you want different gesture recognition in two different views, put separate recognizers on each view.

Answer 2

Usually, you want to have your view controller own and manage gesture recognizers, e.g.
- (void)viewDidLoad {
self.panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(handleGesture:)];
self.panGesture.delegate = self;
[self.viewX addGestureRecognizer:self.panGesture];
// repeat with other recognisers...
}
Note that setting your controller as delegate of the gestureRecognizer is important: this enables you to handle the following delegate method from the view controller (which was the main question):
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
// handle your logic, which gestureRecognizer should proceed...
return NO;
}
The handler method is the same is this example, but you can set up your own handlers as you like:
- (void)handleGesture:(UIGestureRecognizer*)gestureRecognizer {
// handle gesture (usually sorted by state), e.g.
// if(gesture.state == UIGestureRecognizerStateEnded) { ... }
}