Summary

BFDragGestureRecognizer is a UIGestureRecognizer subclass that can be used to drag views inside a scroll view with automatic scrolling at the edges of the scroll view.

Instructions

Create a Podfile, if you don't have one already. Add the following line.

pod 'BFDragGestureRecognizer'

Run the following command.

pod install

Alternatively, you can just drop the BFDragGestureRecognizer.{h,m} files into your project.

Add the gesture recognizer to the view(s) you want to drag:

BFDragGestureRecognizer *dragRecognizer = [[BFDragGestureRecognizer alloc] init];
[dragRecognizer addTarget:self action:@selector(dragRecognized:)];
[view addGestureRecognizer:dragRecognizer];

Implement the gesture handler method. This is very similar to what you would do using a standard UIPanGestureRecognizer:

- (void)dragRecognized:(BFDragGestureRecognizer *)recognizer {
    UIView *view = recognizer.view;
    if (recognizer.state == UIGestureRecognizerStateBegan) {
        // When the gesture starts, remember the current position.
        _startCenter = view.center;
    } else if (recognizer.state == UIGestureRecognizerStateChanged) {
        // During the gesture, we just add the gesture's translation to the saved original position.
        // The translation will account for the changes in contentOffset caused by auto-scrolling.
        CGPoint translation = [recognizer translationInView:_contentView];
        CGPoint center = CGPointMake(_startCenter.x + translation.x, 
                                     _startCenter.y + translation.y);
        view.center = center;
    } 
}

License

New BSD License. For the full license text, see here.