title: iOS animate scroll view
body: <p>I'd like a custom gesture so that if the user slides his/her finger up from the bottom of the screen it displays a scroll view that occupies the bottom fourth of the screen. Similarly, to close the view, the user slides his/her finger downwards off the screen. I am mostly having trouble figuring out how to connect the gesture with the animation so that the view slides up and down as the user moves his/her finger.</p>