安卓 : Z-index of a "RecyclerView.ItemDecoration"

Question

我有一个带有 2 个 ItemDecorations 的 RecyclerView。我如何指定每个 ItemDecoration 的高度(z-index)，以设置将绘制在另一个之上？

Answer 1

来自documentation for RecyclerView.addItemDecoration() :

Item decorations are ordered. Decorations placed earlier in the list will be run/queried/drawn first for their effects on item views. Padding added to views will be nested; a padding added by an earlier decoration will mean further item decorations in the list will be asked to draw/pad within the previous decoration's given area.

所以基本上，如果你写:

recycler.addItemDecoration(decoration1);
recycler.addItemDecoration(decoration2);

绘图将是:

1. decoration1.onDraw
2. decoration2.onDraw
3. 普通的RecyclerView绘图
4. decoration1.onDrawOver
5. decoration2.onDrawOver

这样做的结果是，稍后添加的 ItemDecoration 将绘制在先前添加的那些之上。 z-index 在技术上仍然是相同的，但如果 decoration1 全部绘制为蓝色，而 decoration2 将相同的内容绘制为红色，您会看到红色。