LazyScrollView内部原理分析
首先来看一个简单的案例：
根据DataSource获取所有的TMMuiRectModel
根据DataSource的Delegate，拿到所有的View应该被显示的位置。这一步，核心是拿到的位置是确定的。根据Demo，我们观察从 0/1 - 2/3 之间这些View，这个时候LazyScrollView拿到的Rect如下：
| Index | 标号(MUIID) | Rect |
|---|---|---|
| 0 | 0/0 | origin = (x = 25, y = 15), size = (width = 156, height = 150 |
| 1 | 0/1 | origin = (x = 194, y = 15), size = (width = 156, height = 150) |
| 2 | 0/2 | origin = (x = 25, y = 180), size = (width = 156, height = 150) |
| 3 | 0/3 | origin = (x = 194, y = 180), size = (width = 156, height = 150 |
| 4 | 1/0 | origin = (x = 5, y = 360), size = (width = 177.5, height = 150) |
| 5 | 1/1 | origin = (x = 192.5, y = 426), size = (width = 84, height = 84) |
| 6 | 1/2 | origin = (x = 192.5, y = 360), size = (width = 177.5, height = 56) |
| 7 | 1/3 | origin = (x = 286.5, y = 426), size = (width = 83.5, height = 84) |
| 8 | 2/0 | origin = (x = 25, y = 530), size = (width = 325, height = 150) |
| 9 | 2/1 | origin = (x = 25, y = 695), size = (width = 325, height = 150) |
| 10 | 2/2 | origin = (x = 25, y = 860), size = (width = 325, height = 150) |
排序
拿到了这些位置之后，接下来做的事情就是排序。排序生成的索引会有两个：根据顶边(y)升序排序的索引和根据底边(y+height)降序排序的索引。
根据顶边(y)升序排序的索引
| Index | 标号(MUIID) | Rect |
|---|---|---|
| 0 | 0/0 | origin = (x = 25, y = 15), size = (width = 156, height = 150 |
| 1 | 0/1 | origin = (x = 194, y = 15), size = (width = 156, height = 150) |
| 2 | 0/2 | origin = (x = 25, y = 180), size = (width = 156, height = 150) |
| 3 | 0/3 | origin = (x = 194, y = 180), size = (width = 156, height = 150 |
| 4 | 1/0 | origin = (x = 5, y = 360), size = (width = 177.5, height = 150) |
| 5 | 1/1 | origin = (x = 192.5, y = 360), size = (width = 177.5, height = 56) |
| 6 | 1/2 | origin = (x = 192.5, y = 360), size = (width = 177.5, height = 56) |
| 7 | 1/3 | origin = (x = 286.5, y = 426), size = (width = 83.5, height = 84) |
| 8 | 2/0 | origin = (x = 25, y = 530), size = (width = 325, height = 150) |
| 9 | 2/1 | origin = (x = 25, y = 695), size = (width = 325, height = 150) |
| 10 | 2/2 | origin = (x = 25, y = 860), size = (width = 325, height = 150) |
