Dragging an uiview like facebooks menu slide

Question

I know this has been probably asked before but I've seen many approaches and i don't know which is best for me, so plz don't send me a link to another post unless it addresses my problem directly.

I have a controller which has a uiview on the top (like a header) (this header is bigger than it seems because is partially hidden on top). on that view i have a uibutton which now with a touch up inside shows the entire header view and taping again returns it to its starting position (changing frame with animation). I want to also be able to drag the view but only changing position on the y axis(dragging up and down)... i was thinking of adding the dragInside/Outside event to the button but this doesn't give me the position of the finger... and also want to know when the user releases the drag so the view ends animation to any of its two possible states (showing or partially hidden). Is this a "touches began" , "touches moved" , "touches ended" thing? if it is please provide a code example. I also want to do this with another view but this is on the left side... same thing but this one moves on the X axis... any help is appreciated. or maybe it can be made with drag event if i only can save a CGpoint of last touch, maybe that's better, any other suggestions

Answer 1

Look at using a UIPanGestureRecognizer to detect the touch movements. Use the translationInView: of the gesture to set the view y position. The translation is the total movement since the start of the gesture so you don't need to remember and accumulate the offset position yourself.

The main thing to worry about while implementing this is bounding the y position of the view so that no matter how far the user drags the view won't go too high or low on the screen.

Answer 2

Use a UIPanGestureRecognizer, that's a class dedicated to handling such drag/pan gestures.

Everything is described here in Apple's documentation, including examples, so you should find your answer here.

There is also some sample code in Apple Developer Library that shows you how to use Gesture Recognizers if needed.