在另一个视图控制器中检测到LongPressGesture已结束

Question

I have a LongPressGesture recogniser which when a long press is detected it presents a new segue:

if (gestureRecognizer.state == UIGestureRecognizerStateBegan) {

            [self performSegueWithIdentifier:@"showImage" sender:self];
}

The problem being i want the new 'segue' to detect that the gesture had ended and revert back to the previous view controller :

if (gestureRecognizer.state == UIGestureRecognizerStateEnded) {

   [self presentViewController:friendViewController animated:YES completion:Nil];
}

I have tried to set up a new gesture recogniser in the new segue but it isn't detected unless the user ends the previous gesture.

Answer 1

You're doing (or trying to do) several things incorrectly. When you segue to the new controller, the long press recognizer's state will go to "failed", so there's nothing more you can do with it. There's no way to add a gesture recognizer to the new controller's view that will accept your previous touch as the beginning of its touch, so that's not going to work. Also, if you want to go back to your previous controller, you shouldn't use presentViewController, that just creates a new instance of friendViewController; it doesn't go back to the old one.

I think the way you need to accomplish your goal, is not to present a new controller, but to add a new view on top of the one with the gesture recognizer. In the example below, I just create a simple view for demonstration purposes, but you could create one in a xib if you need something more complicated.

-(IBAction)handleLongPress:(UILongPressGestureRecognizer *)sender {

    if (sender.state == UIGestureRecognizerStateBegan) {
        UIView *newView = [[UIView alloc] initWithFrame:self.view.bounds];
        newView.backgroundColor = [UIColor redColor];
        newView.tag = 10;
        [self.view addSubview:newView];
    }

    if (sender.state == UIGestureRecognizerStateEnded) {
        [[self.view viewWithTag:10] removeFromSuperview];
    }
}