Loop Scroll Rect

v1.03

This project works for Unity 5.2 or newer. I havn't tested older versions and any Pull Requests are welcomed.

These scripts help make your ScrollRect Reusable, because it will only build cells when needed. If you have a large number of cells in a scroll rect, you absolutely need it! It will save a lot of time loading and draw call, along with memory in use, while still working smoothly.

中文说明请看这里。

Demo

Demo for Loop Scroll Rect. Each cell knows its own index, and it is able to modify its content/size/color easily.

Also ScrollBar is supported now! It supports both vertical & horizontal directions, back and forth.

Demo without mask. As you can see, the cells are only instantiated when needed and recycled.

Introduction

The original idea comes from @ivomarel's InfinityScroll. After serveral refactorisations, I almost rewrite all the codes:

Avoid using sizeDelta directly since it doesn't always mean size
Support GridLayout
Avoid blocking when dragging back
Take advantage of pool rather than instantiate/destroy every time
Improve some other details for performance
Supports reverse direction
Supports ScrollBar (this doesn't work in Infinite mode, and may behavior strange for cells with different size)

Also, I modified Easy Object Pool for recycling the cells.

My scripts copies ScrollRect from UGUI rather than inherit ScrollRect like InfinityScroll. I need to modify some private variants to make dragging smooth. All my codes is wrapped with comments like ==========LoopScrollRect==========, making maintaining a little easier.

Infinite Version

If you need scroll infinitely, you can simply set totalCount to a negative number.

Quick Jump

As some people having the same issue here: how to jump to a specified cell directly:

Add a Coroutine for tween. As you can check the children by yourself, it is easy to find the right time to stop. However this is not elegant.
I've already provided a method called RefillCells(int offset = 0). For example RefillCells(3) means a LoopScroll with idx=3 as the first cell. But your lose the animation now.

Example: Loop Vertical Scroll Rect

These steps may be confusing, so you can just open the demo scene and copy & paste :D

You can also remove EasyObjPool and use your pool instead.

Prepare cell prefabs
- The cell needs Layout Element attached and preferred width/height
- You should add a script receiving message void ScrollCellIndex (int idx)

Right click in Hierarchy and click UI/Loop Horizontal Scroll Rect or UI/Loop Vertical Scroll Rect. It is the same for these two in the Component Menu.
- Init in Start: call Refill cells automatically when Start
- Prefab Pool: the EasyObjPool gameObject
- Prefab Pool Name: the corresponding pool in step 1
- Total Count: How many cells are available (index: 0 ~ TotalCount-1)
- Threshold: How many additional pixels of content should be prepared before start or after end?
- ReverseDirection: If you want scroll from bottom or right, you should toggle this
- Clear Cells: remove existing cells and keep uninitialized
- Refill Cells: initialize and fill up cells

If you need scroll from top or left, setting content's pivot to 1 and disable ReverseDirection. Otherwise, you should set 0 to pivot and enable ReverseDirection (I have made VerticalScroll_Reverse in the demo scene as reference).

I highly suggests you trying these parameters by hand. More details can be found in the demo scene.