Disabling Pan Gesture if out of bounds detected

Question

I have a UIView I am trying to move up and down the screen, however I only wish to enable it to pan so that you cannot drag the view down when it is in its normal position (0, 0)

I tried to detect when the recognizer's center is not half the height of the view, however the view is then immovable, and the center is always half the height (230 in this case).

Any ideas?

- (IBAction)panDetected:(UIPanGestureRecognizer *)recognizer {
    CGPoint translation = [recognizer translationInView:self.view];
    NSLog(@"\ncenter.y: %f\ntranslation.y: %f\n", recognizer.view.center.y, translation.y);
    if (recognizer.view.center.y > ([[UIScreen mainScreen] bounds].size.height - 20)/2) {
            return;
    }
    recognizer.view.center = CGPointMake(recognizer.view.center.x,
                                         recognizer.view.center.y + translation.y);
    [recognizer setTranslation:CGPointMake(0, 0) inView:self.view];
}

Answer 1

recognizer.view.center = CGPointMake(recognizer.view.center.x, MAX(recognizer.view.center.y + translation.y, ([[UIScreen mainScreen] bounds].size.height - 20)/2));