这个问题的答案似乎比他们应该做的要复杂。以下是我的看法。

假设您希望网格项之间有1dp的间距。做以下几点:

为每个项目添加0.5dp的填充 给RecycleView添加-0.5dp的填充 就是这样!：）

对我来说，完美的解决方案是设置RecyclerView的宽度它的layoutmanager为GridLayoutManager为wrap_content

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。

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));

只有一个简单的解决方案，您可以记住并在任何需要的地方实施。没有bug，没有疯狂的计算。在卡片/物品布局中放置空白，并在RecyclerView中放置相同大小的填充:

item_layout.xml

<CardView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:margin="10dp">

activity_layout.xml

<RecyclerView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="10dp"/>

更新:

感谢edwardaa的回答https://stackoverflow.com/a/30701422/2227031

另一点需要注意的是:

如果total spacing和total itemWidth不等于屏幕宽度，您还需要调整itemWidth，例如，在适配器onBindViewHolder方法

Utils.init(_mActivity);
int width = 0;
if (includeEdge) {
    width = ScreenUtils.getScreenWidth() - spacing * (spanCount + 1);
} else {
    width = ScreenUtils.getScreenWidth() - spacing * (spanCount - 1);
}
int itemWidth = width / spanCount;

ConstraintLayout.LayoutParams layoutParams = (ConstraintLayout.LayoutParams) holder.imageViewAvatar.getLayoutParams();
// suppose the width and height are the same
layoutParams.width = itemWidth;
layoutParams.height = itemWidth;
holder.imageViewAvatar.setLayoutParams(layoutParams);