这也适用于RecyclerView with header。

public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {

    private int spanCount;
    private int spacing;
    private boolean includeEdge;
    private int headerNum;

    public GridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge, int headerNum) {
        this.spanCount = spanCount;
        this.spacing = spacing;
        this.includeEdge = includeEdge;
        this.headerNum = headerNum;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        int position = parent.getChildAdapterPosition(view) - headerNum; // item position

        if (position >= 0) {
            int column = position % spanCount; // item column

            if (includeEdge) {
                outRect.left = spacing - column * spacing / spanCount; // spacing - column * ((1f / spanCount) * spacing)
                outRect.right = (column + 1) * spacing / spanCount; // (column + 1) * ((1f / spanCount) * spacing)

                if (position < spanCount) { // top edge
                    outRect.top = spacing;
                }
                outRect.bottom = spacing; // item bottom
            } else {
                outRect.left = column * spacing / spanCount; // column * ((1f / spanCount) * spacing)
                outRect.right = spacing - (column + 1) * spacing / spanCount; // spacing - (column + 1) * ((1f /    spanCount) * spacing)
                if (position >= spanCount) {
                    outRect.top = spacing; // item top
                }
            }
        } else {
            outRect.left = 0;
            outRect.right = 0;
            outRect.top = 0;
            outRect.bottom = 0;
        }
    }
    }
}

对于这个问题，有一个非常简单而灵活的解决方案，它只使用适用于每个LayoutManager的XML。

假设你想要一个相等的X间距(例如8dp)。

在另一个布局中包装CardView项 给外层布局填充X/2 (4dp) 使外层布局背景透明

...

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="200dp"
    android:layout_height="200dp"
    android:background="@android:color/transparent"
    android:padding="4dip">

    <android.support.v7.widget.CardView
        android:layout_width="match_parent"
        android:layout_height="match_parent">
    </android.support.v7.widget.CardView>

</LinearLayout>

给你的RecyclerView填充X/2 (4dp)

...

<android.support.v7.widget.RecyclerView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="4dp" />

就是这样。你有完美的X (8dp)间距。

如果你使用Header和GridLayoutManager，使用以下代码在Kotlin中编写的网格间距:

inner class SpacesItemDecoration(itemSpace: Int) : RecyclerView.ItemDecoration() {

    var space: Int = itemSpace

    override fun getItemOffsets(outRect: Rect?, view: View?, parent: RecyclerView?, state: RecyclerView.State?) {
        super.getItemOffsets(outRect, view, parent, state)
        val position = parent!!.getChildAdapterPosition(view)
        val viewType = parent.adapter.getItemViewType(position)
        
        // Check to not to set any margin to header item 
        if (viewType == GridViewAdapter.TYPE_HEADER) {
            outRect!!.top = 0
            outRect.left = 0
            outRect.right = 0
            outRect.bottom = 0
        } else {
            outRect!!.left = space
            outRect.right = space
            outRect.bottom = space

            if (parent.getChildLayoutPosition(view) == 0) {
                outRect.top = space
            } else {
                outRect.top = 0
            }
        }
    }
}

并将ItemDecoration传递给RecyclerView为:

gridView.addItemDecoration(SpacesItemDecoration(10))

这是我对SpacesItemDecoration的修改，它可以在顶部，底部，左边和右边同样采取numofcolumns和空间。

public class SpacesItemDecoration extends RecyclerView.ItemDecoration {
    private int space;
    private int mNumCol;

    public SpacesItemDecoration(int space, int numCol) {
        this.space = space;
        this.mNumCol=numCol;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view,
                               RecyclerView parent, RecyclerView.State state) {

        //outRect.right = space;
        outRect.bottom = space;
        //outRect.left = space;

        //Log.d("ttt", "item position" + parent.getChildLayoutPosition(view));
        int position=parent.getChildLayoutPosition(view);

        if(mNumCol<=2) {
            if (position == 0) {
                outRect.left = space;
                outRect.right = space / 2;
            } else {
                if ((position % mNumCol) != 0) {
                    outRect.left = space / 2;
                    outRect.right = space;
                } else {
                    outRect.left = space;
                    outRect.right = space / 2;
                }
            }
        }else{
            if (position == 0) {
                outRect.left = space;
                outRect.right = space / 2;
            } else {
                if ((position % mNumCol) == 0) {
                    outRect.left = space;
                    outRect.right = space/2;
                } else if((position % mNumCol) == (mNumCol-1)){
                    outRect.left = space/2;
                    outRect.right = space;
                }else{
                    outRect.left=space/2;
                    outRect.right=space/2;
                }
            }

        }

        if(position<mNumCol){
            outRect.top=space;
        }else{
            outRect.top=0;
        }
        // Add top margin only for the first item to avoid double space between items
        /*
        if (parent.getChildLayoutPosition(view) == 0 ) {

        } else {
            outRect.top = 0;
        }*/
    }
}

并在逻辑上使用下面的代码。

recyclerView.addItemDecoration(new SpacesItemDecoration(spacingInPixels, numCol));

Yqritc的回答非常适合我。我用的是Kotlin，这里有一个等价物。

class ItemOffsetDecoration : RecyclerView.ItemDecoration  {

    // amount to add to padding
    private val _itemOffset: Int

    constructor(itemOffset: Int) {
        _itemOffset = itemOffset
    }

    constructor(@NonNull context: Context, @DimenRes itemOffsetId: Int){
       _itemOffset = context.resources.getDimensionPixelSize(itemOffsetId)
    }

    /**
     * Applies padding to all sides of the [Rect], which is the container for the view
     */
    override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView,state: RecyclerView.State) {
        super.getItemOffsets(outRect, view, parent, state)
        outRect.set(_itemOffset, _itemOffset, _itemOffset, _itemOffset)
    }
}

其他一切都是一样的。

class VerticalGridSpacingDecoration(private val spacing: Int) : RecyclerView.ItemDecoration() {

  override fun getItemOffsets(
    outRect: Rect,
    view: View,
    parent: RecyclerView,
    state: State
  ) {
    val layoutManager = parent.layoutManager as? GridLayoutManager
    if (layoutManager == null || layoutManager.orientation != VERTICAL) {
      return super.getItemOffsets(outRect, view, parent, state)
    }

    val spanCount = layoutManager.spanCount
    val position = parent.getChildAdapterPosition(view)
    val column = position % spanCount
    with(outRect) {
      left = if (column == 0) 0 else spacing / 2
      right = if (column == spanCount.dec()) 0 else spacing / 2
      top = if (position < spanCount) 0 else spacing
    }
  }
}