RecyclerView GridLayoutManager项装饰需要占用空间吗？

Question

我正在创建一个具有三列的垂直RecyclerView（为简化说明，我使RecyclerView仅包含6个项目）。我需要的是两侧的物品都具有更大的边距，因此我使用ItemDecoration来实现这一点：

class SpaceDecoration : RecyclerView.ItemDecoration() {

    override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
        val position = parent.getChildAdapterPosition(view)
        outRect.left = when(position) {
            0, 3 -> 160 // Left most two items
            else -> 10 // others
        }
        outRect.right = when(position) {
            2, 5 -> 160 // Right most two items
            else ->0 // others
        }
        outRect.top = 10
        outRect.bottom = 0
    }
}

我想要的是项目主体具有相同的宽度。但是，事实并非如此。看起来GridLayoutManager在平均划分空间时会测量ItemDecoration的大小。如何使项目看起来相等的宽度？我当然不希望GridLayoutManager测量ItemDecoration。

这是剩余的代码：

MainActivity.kt：

class MainActivity : AppCompatActivity() {
    private lateinit var recyclerView: RecyclerView

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        recyclerView = findViewById(R.id.grid)
        recyclerView.layoutManager = GridLayoutManager(this,3,  RecyclerView.VERTICAL, false)
        recyclerView.adapter = GridAdapter()
        recyclerView.addItemDecoration(SpaceDecoration())
    }
}

GridAdapter.kt：

class GridAdapter : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder =
        VH(LayoutInflater.from(parent.context).inflate(R.layout.grid_item, parent, false))
    override fun getItemCount() = 6
    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) = Unit
    class VH(item: View) : RecyclerView.ViewHolder(item)
}

grid_item.xml：

<?xml version="1.0" encoding="utf-8"?>
<TextView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:textSize="48sp"
    android:text="AAA"
    android:gravity="center"
    android:background="@color/colorAccent"/>

Answer 1

您可以将paddingLeft和paddingRight添加到recyclerView中（不添加任何ItemDecoration）。会有填充，元素的大小将相等。