当为儿童使用CardView时，项目之间的空格问题可以通过设置app:cardUseCompatPadding为true来解决。

为更大的边际扩大项目抬高。CardElevation是可选的(使用默认值)。

<androidx.cardview.widget.CardView
    xmlns:app="http://schemas.android.com/apk/res-auto"
    app:cardUseCompatPadding="true"
    app:cardElevation="2dp">

如果你想在所有设备中固定你的RecyclerView项的大小。你可以这样做

public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {

    private int mSpanCount;
    private float mItemSize;

    public GridSpacingItemDecoration(int spanCount, int itemSize) {
        this.mSpanCount = spanCount;
        mItemSize = itemSize;
    }

    @Override
    public void getItemOffsets(final Rect outRect, final View view, RecyclerView parent,
            RecyclerView.State state) {
        final int position = parent.getChildLayoutPosition(view);
        final int column = position % mSpanCount;
        final int parentWidth = parent.getWidth();
        int spacing = (int) (parentWidth - (mItemSize * mSpanCount)) / (mSpanCount + 1);
        outRect.left = spacing - column * spacing / mSpanCount;
        outRect.right = (column + 1) * spacing / mSpanCount;

        if (position < mSpanCount) {
            outRect.top = spacing;
        }
        outRect.bottom = spacing;
    }
}

recyclerview_item.xml

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="@dimen/recycler_view_item_width" 
    ...
    >
    ...
</LinearLayout>

dimens.xml

 <dimen name="recycler_view_item_width">60dp</dimen>

活动

int numberOfColumns = 3;
mRecyclerView.setLayoutManager(new GridLayoutManager(this, numberOfColumns));
mRecyclerView.setAdapter(...);
mRecyclerView.addItemDecoration(new GridSpacingItemDecoration(3,
        getResources().getDimensionPixelSize(R.dimen.recycler_view_item_width)));

RecyclerViews支持ItemDecoration的概念:围绕每个元素的特殊偏移和绘图。从这个答案中可以看出，你可以使用

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

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

  @Override
  public void getItemOffsets(Rect outRect, View view, 
      RecyclerView parent, RecyclerView.State state) {
    outRect.left = space;
    outRect.right = space;
    outRect.bottom = space;

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

然后通过

mRecyclerView = (RecyclerView) rootView.findViewById(R.id.my_recycler_view);
int spacingInPixels = getResources().getDimensionPixelSize(R.dimen.spacing);
mRecyclerView.addItemDecoration(new SpacesItemDecoration(spacingInPixels));

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;
        }
    }
    }
}

下面是一个不需要“spanCount”(列数)的解决方案 我使用它是因为我使用GridAutofitLayoutManager(根据所需的单元格大小计算列数)

(注意，这将只工作在GridLayoutManager)

public class GridSpacesItemDecoration extends RecyclerView.ItemDecoration {
    private final boolean includeEdge;
    private int spacing;


    public GridSpacesItemDecoration(int spacing, boolean includeEdge) {
        this.spacing = spacing;
        this.includeEdge = includeEdge;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        if (parent.getLayoutManager() instanceof GridLayoutManager) {
            GridLayoutManager layoutManager = (GridLayoutManager)parent.getLayoutManager();
            int spanCount = layoutManager.getSpanCount();
            int position = parent.getChildAdapterPosition(view); // item position
            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
                }
            }

        }

    }
}

这是GridAutofitLayoutManager是谁感兴趣:

public class GridAutofitLayoutManager extends GridLayoutManager {
    private int mColumnWidth;
    private boolean mColumnWidthChanged = true;

    public GridAutofitLayoutManager(Context context, int columnWidth)
    {
        /* Initially set spanCount to 1, will be changed automatically later. */
        super(context, 1);
        setColumnWidth(checkedColumnWidth(context, columnWidth));
    }

    public GridAutofitLayoutManager(Context context,int unit, int columnWidth)
    {
        /* Initially set spanCount to 1, will be changed automatically later. */
        super(context, 1);
        int pixColumnWidth = (int) TypedValue.applyDimension(unit, columnWidth, context.getResources().getDisplayMetrics());
        setColumnWidth(checkedColumnWidth(context, pixColumnWidth));
    }

    public GridAutofitLayoutManager(Context context, int columnWidth, int orientation, boolean reverseLayout)
    {
        /* Initially set spanCount to 1, will be changed automatically later. */
        super(context, 1, orientation, reverseLayout);
        setColumnWidth(checkedColumnWidth(context, columnWidth));
    }

    private int checkedColumnWidth(Context context, int columnWidth)
    {
        if (columnWidth <= 0)
        {
            /* Set default columnWidth value (48dp here). It is better to move this constant
            to static constant on top, but we need context to convert it to dp, so can't really
            do so. */
            columnWidth = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 48,
                    context.getResources().getDisplayMetrics());
        }
        return columnWidth;
    }

    public void setColumnWidth(int newColumnWidth)
    {
        if (newColumnWidth > 0 && newColumnWidth != mColumnWidth)
        {
            mColumnWidth = newColumnWidth;
            mColumnWidthChanged = true;
        }
    }

    @Override
    public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state)
    {
        int width = getWidth();
        int height = getHeight();
        if (mColumnWidthChanged && mColumnWidth > 0 && width > 0 && height > 0)
        {
            int totalSpace;
            if (getOrientation() == VERTICAL)
            {
                totalSpace = width - getPaddingRight() - getPaddingLeft();
            }
            else
            {
                totalSpace = height - getPaddingTop() - getPaddingBottom();
            }
            int spanCount = Math.max(1, totalSpace / mColumnWidth);
            setSpanCount(spanCount);

            mColumnWidthChanged = false;
        }
        super.onLayoutChildren(recycler, state);
    }
}

最后:

mDevicePhotosView.setLayoutManager(new GridAutofitLayoutManager(getContext(), getResources().getDimensionPixelSize(R.dimen.item_size)));
mDevicePhotosView.addItemDecoration(new GridSpacesItemDecoration(Util.dpToPx(getContext(), 2),true));

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!：）