How to limit pan gesture area?

问题

I am having my UIImageView onto which I am having another UIView rectangle. By applying pan gesture to UIView rectangle it gets outside of UIImageView also. I don't want to be drag outside of UIImageView

I have tried below code but it is not working that way

-(void)handleMovementView:(UIPanGestureRecognizer *)recognizer
{
    CGPoint movement;

    if(recognizer.state == UIGestureRecognizerStateBegan || recognizer.state == UIGestureRecognizerStateChanged || recognizer.state == UIGestureRecognizerStateEnded)
    {
        CGRect rec = recognizer.view.frame;
        CGRect imgvw = self.imgViewCrop.frame;
        if((rec.origin.x >= imgvw.origin.x && (rec.origin.x + rec.size.width <= imgvw.origin.x + imgvw.size.width)))
        {
            CGPoint translation = [recognizer translationInView:recognizer.view.superview];
            movement = translation;
            recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x, recognizer.view.center.y + translation.y);
            [recognizer setTranslation:CGPointZero inView:recognizer.view.superview];
            [self handleMovementForHandlers:movement];
        }
    }

}

If i apply Pan slowly it applies this condition but when i go fast it went outside of ImageView

回答1:

Try This

-(void)handleMovementView:(UIPanGestureRecognizer *)recognizer
{
CGPoint movement;

if(recognizer.state == UIGestureRecognizerStateBegan || recognizer.state == UIGestureRecognizerStateChanged || recognizer.state == UIGestureRecognizerStateEnded)
{
    CGRect rec = recognizer.view.frame;
    CGRect imgvw = self.imgViewCrop.frame;
    if((rec.origin.x >= imgvw.origin.x && (rec.origin.x + rec.size.width <= imgvw.origin.x + imgvw.size.width)))
    {
        CGPoint translation = [recognizer translationInView:recognizer.view.superview];
        movement = translation;
        recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x, recognizer.view.center.y + translation.y);
        rec = recognizer.view.frame;

        if( rec.origin.x < imgvw.origin.x )
            rec.origin.x = imgvw.origin.x;

        if( rec.origin.x + rec.size.width > imgvw.origin.x + imgvw.size.width )
            rec.origin.x = imgvw.origin.x + imgvw.size.width - rec.size.width;

        recognizer.view.frame = rec;

        [recognizer setTranslation:CGPointZero inView:recognizer.view.superview];
        [self handleMovementForHandlers:movement];
    }
}
}

回答2:

Instead of manually computing whether the points are within the view's bounds, use CGRectContainsPoint(rect, point). This is what works for me, and I like it because it's shorter and more readable:

func handlePan(pan: UIPanGestureRecognizer) {
    switch pan.state {
    case .Began:
        if CGRectContainsPoint(self.pannableView.frame, pan.locationInView(self.pannableView)) {
            // Gesture started inside the pannable view. Do your thing.
        }
}

回答3:

First get the coordinate (CGRect) of recognizer(Pan Gesture recognizer) then get coordinate (CGRect) of ImageView(Your ImageView).

And then compare this coordinate according to your requirement.

If you are still facing any problem then log the x and y value of image view and recognizer.

回答4:

Expanding on @Matt Quiros' answer, and in Swift 3 / 4:

func shouldRespondToGesture(_ gesture: UIGestureRecognizer, in frame: CGRect) -> Bool {
    return gesture.state == .began && frame.contains(gesture.location(in: self.view))
}

来源：https://stackoverflow.com/questions/12048525/how-to-limit-pan-gesture-area