Moving a scroll view from code, one item at a time

[madmat3001]

I followed this example to create a scroll view that centers on items.

So far everything works fine, but now I want to add buttons that can move the scroll view one item left / right at a time.

I'm using DraggablePanel.MoveRelative() to move the panel and I am splitting the move over a few frames to make it look smooth.

Now sometimes this works perfectly, but sometimes the position of the DraggablePanel is changed between two calls of MoveRelative() and as a result the panel wont move far enough for the centering to center on the next item.

I have already tried to disable the UICenterOnItem Script during the move and re-enabling it after, which did not help.

What other components might be changing the DraggablePanel's position?

[ArenMook]

Easiest way to find out is to put some Debug.Log statements in that script. Off the top of my head I can't tell you much.

[madmat3001]

Yeah, I've tried that. I can say for sure, that no other component is calling MoveRelative() (or MoveAbsolute() for that matter).

But I have just found a component "SpringPanel" that's attached to my DraggablePanel during runtime, but not during design time (Which is why I haven't noticed it 'til now). I have not yet dug deeply into the code, but at first glance it seems like a possible culprit.

What does it do and where does it come from?

[ArenMook]

SpringPanel is what's used to move the panel when you let go of the mouse button/touch. It adds a "spring" effect to it rather than stopping movement outright.

[madmat3001]

Fixed it.

It was indeed the SpringPanel which caused all my troubles. Now while the SpringPanel is usually only enabled for a short time, it sometimes stayed enabled after I moved the DraggablePanel using MoveRelative().

Now the next time I hit my button to move the DraggablePanel, the SpringPanel would still be enabled and "counter act" my movement to a certain degree, resulting in the weird behaviour.

So for anybody else trying to implement "up/down" or "left/right" buttons for their scroll views, make sure to disable the SpringPanel before you call DraggablePanel.MoveRelative()

I wonder how nobody had this problem before, as I'm sure having scroll button like this is a rather common feature, isn't it?

[ArenMook]

I guess not!