使用GridLayoutManager装饰RecyclerView以显示项目之间的分隔符

Question

如何以最佳和最简单的方式装饰RecyclerView，使其具有这样的外观和感觉？

这里的主要挑战是仅在项目之间拥有分隔线，而不是在项目和屏幕左/右边框之间拥有分隔线。

有任何想法吗？

- AlexKorovyansky

---

请参见 https://developer.android.com/reference/android/support/v7/widget/RecyclerView.ItemDecoration.html#getItemOffsets(android.graphics.Rect, android.view.View, android.support.v7.widget.RecyclerView, android.support.v7.widget.RecyclerView.State)。 - pskink

@pskink 我看到需要创建/重用某种项目装饰，问题是关于具体解决方案。 - AlexKorovyansky

@pskink，确定getItemOffsets方法中的项是否具有右/左邻居的正确方法是什么？ - AlexKorovyansky

RecyclerView.getChildPosition(View child) 方法可以获取子项的位置，而该位置决定了该项在 RecyclerView 中的布局位置。 - pskink

@pskink 怎样理解它是否在边界附近（一般情况下）？ - AlexKorovyansky

Answer 1

我不知道你为什么需要那个，但是使用RecyclerView装饰器实现这个UI非常容易。

<!--Integer Value that number of column in RecyclerView-->
<integer name="photo_list_preview_columns">3</integer>

<!-- inter spacing between RecyclerView's Item-->
<dimen name="photos_list_spacing">10dp</dimen>

根据您的需求，您可以更改 photo_list_preview_columns 和 photos_list_spacing。

mRecylerView.addItemDecoration(new ItemDecorationAlbumColumns(
    getResources().getDimensionPixelSize(R.dimen.photos_list_spacing), 
    getResources().getInteger(R.integer.photo_list_preview_columns)));

需要进行一些重构的"and decorator"

import android.graphics.Rect;
import android.support.v7.widget.RecyclerView;
import android.view.View;

public class ItemDecorationAlbumColumns extends RecyclerView.ItemDecoration {

    private int mSizeGridSpacingPx;
    private int mGridSize;

    private boolean mNeedLeftSpacing = false;

    public ItemDecorationAlbumColumns(int gridSpacingPx, int gridSize) {
        mSizeGridSpacingPx = gridSpacingPx;
        mGridSize = gridSize;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        int frameWidth = (int) ((parent.getWidth() - (float) mSizeGridSpacingPx * (mGridSize - 1)) / mGridSize);
        int padding = parent.getWidth() / mGridSize - frameWidth;
        int itemPosition = ((RecyclerView.LayoutParams) view.getLayoutParams()).getViewAdapterPosition();
        if (itemPosition < mGridSize) {
            outRect.top = 0;
        } else {
            outRect.top = mSizeGridSpacingPx;
        }
        if (itemPosition % mGridSize == 0) {
            outRect.left = 0;
            outRect.right = padding;
            mNeedLeftSpacing = true;
        } else if ((itemPosition + 1) % mGridSize == 0) {
            mNeedLeftSpacing = false;
            outRect.right = 0;
            outRect.left = padding;
        } else if (mNeedLeftSpacing) {
            mNeedLeftSpacing = false;
            outRect.left = mSizeGridSpacingPx - padding;
            if ((itemPosition + 2) % mGridSize == 0) {
                outRect.right = mSizeGridSpacingPx - padding;
            } else {
                outRect.right = mSizeGridSpacingPx / 2;
            }
        } else if ((itemPosition + 2) % mGridSize == 0) {
            mNeedLeftSpacing = false;
            outRect.left = mSizeGridSpacingPx / 2;
            outRect.right = mSizeGridSpacingPx - padding;
        } else {
            mNeedLeftSpacing = false;
            outRect.left = mSizeGridSpacingPx / 2;
            outRect.right = mSizeGridSpacingPx / 2;
        }
        outRect.bottom = 0;
    }
}

- Dmitry L.

---

谢谢，Dmitry！像魔法一样好用！ - AlexKorovyansky

@AlexKorovyansky 如何实现相同的用户界面，但带有“加载更多项目”的功能？ - Erum

如果可以的话，我会直接过来拥抱你兄弟。这就是我一直在寻找的东西。谢谢。 - viper

mNeedLeftSpacing状态变量的含义是什么？它是否依赖于调用顺序？ - Vladimir Berezkin

如果您正在使用ConcatAdapter，则**getViewAdapterPosition()将返回单个适配器项的位置，这是错误的。为此，我们需要使用getAbsoluteAdapterPosition()**，它将返回相对于RecyclerView的实际位置。 - Bhavin

Answer 2

这是一种更简单、更用户友好的实现方式：

public class MediaSpaceDecoration extends RecyclerView.ItemDecoration {
    private final int spacing;
    private final List<Integer> allowedViewTypes = Arrays.asList(
            R.layout.item_image,
            R.layout.item_blur);

    public MediaSpaceDecoration(int spacing) {
        this.spacing = spacing;
    }

    @Override
    public void getItemOffsets(Rect outRect,
                               View view,
                               RecyclerView parent,
                               RecyclerView.State state) {
        final int position = parent.getChildAdapterPosition(view);
        if (!isMedia(parent, position)) {
            return;
        }

        final int totalSpanCount = getTotalSpanCount(parent);
        int spanSize = getItemSpanSize(parent, position);
        if (totalSpanCount == spanSize) {
            return;
        }

        outRect.top = isInTheFirstRow(position, totalSpanCount) ? 0 : spacing;
        outRect.left = isFirstInRow(position, totalSpanCount) ? 0 : spacing / 2;
        outRect.right = isLastInRow(position, totalSpanCount) ? 0 : spacing / 2;
        outRect.bottom = 0; // don't need
    }

    private boolean isInTheFirstRow(int position, int spanCount) {
        return position < spanCount;
    }

    private boolean isFirstInRow(int position, int spanCount) {
        return position % spanCount == 0;
    }

    private boolean isLastInRow(int position, int spanCount) {
        return isFirstInRow(position + 1, spanCount);
    }

    private int getTotalSpanCount(RecyclerView parent) {
        final RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        return layoutManager instanceof GridLayoutManager
            ? ((GridLayoutManager) layoutManager).getSpanCount()
            : 1;
    }

    private int getItemSpanSize(RecyclerView parent, int position) {
        final RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        return layoutManager instanceof GridLayoutManager
            ? ((GridLayoutManager) layoutManager).getSpanSizeLookup().getSpanSize(position)
            : 1;
    }

    private boolean isMedia(RecyclerView parent, int viewPosition) {
        final RecyclerView.Adapter adapter = parent.getAdapter();
        final int viewType = adapter.getItemViewType(viewPosition);
        return allowedViewTypes.contains(viewType);
    }
}

在设置outRect之前，我还进行了检查，因为每个viewType都有不同的spanSize，我只需要为allowedViewTypes添加额外的中间空白。您可以轻松删除该验证并使代码更加简单。对于我来说，它看起来是这样的：

- Nikolay Kulachenko

---

谢谢。我去掉了allowedViewTypes和isMedia，并将outRect.top设置为0，因为我只想在列之间留出空白，而不是在行之间留出空白。 - Sam

如果网格的宽度大于2个图像，则此方法无效，因为您不能仅将间距除以2，而且它取决于图像的位置。更多细节请参见下面的答案：https://dev59.com/BF4b5IYBdhLWcg3wbRIf#63488804 - Inti

item_image和item_blur是什么？ - CoolMind

Answer 3

也许你已经得到了答案，但我还是会发布我的解决方案，以帮助其他人。通过传递方向参数，可以将其用于垂直、水平列表或网格视图。

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;

public class DividerItemDecoration extends RecyclerView.ItemDecoration {

    private static final int[] ATTRS = new int[]{
            android.R.attr.listDivider
    };

    public static final int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL;
    public static final int VERTICAL_LIST = LinearLayoutManager.VERTICAL;
    public static final int GRID = 2;

    private Drawable mDivider;

    private int mOrientation;

    public DividerItemDecoration(Context context, int orientation) {
        final TypedArray a = context.obtainStyledAttributes(ATTRS);
        mDivider = a.getDrawable(0);
        a.recycle();
        setOrientation(orientation);
    }

    public void setOrientation(int orientation) {
        if (orientation != HORIZONTAL_LIST && orientation != VERTICAL_LIST && orientation != GRID) {
            throw new IllegalArgumentException("invalid orientation");
        }
        mOrientation = orientation;
    }

    @Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
        if (mOrientation == VERTICAL_LIST) {
            drawVertical(c, parent);
        } else if(mOrientation == HORIZONTAL_LIST){
            drawHorizontal(c, parent);
        } else {
            drawVertical(c, parent);
            drawHorizontal(c, parent);
        }
    }

    public void drawVertical(Canvas c, RecyclerView parent) {
        if (parent.getChildCount() == 0) return;

        final int left = parent.getPaddingLeft();
        final int right = parent.getWidth() - parent.getPaddingRight();

        final View child = parent.getChildAt(0);
        if (child.getHeight() == 0) return;

        final RecyclerView.LayoutParams params =
                (RecyclerView.LayoutParams) child.getLayoutParams();
        int top = child.getBottom() + params.bottomMargin + mDivider.getIntrinsicHeight();
        int bottom = top + mDivider.getIntrinsicHeight();

        final int parentBottom = parent.getHeight() - parent.getPaddingBottom();
        while (bottom < parentBottom) {
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);

            top += mDivider.getIntrinsicHeight() + params.topMargin + child.getHeight() + params.bottomMargin + mDivider.getIntrinsicHeight();
            bottom = top + mDivider.getIntrinsicHeight();
        }
    }

    public void drawHorizontal(Canvas c, RecyclerView parent) {
        final int top = parent.getPaddingTop();
        final int bottom = parent.getHeight() - parent.getPaddingBottom();

        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            final RecyclerView.LayoutParams params =
                    (RecyclerView.LayoutParams) child.getLayoutParams();
            final int left = child.getRight() + params.rightMargin + mDivider.getIntrinsicHeight();
            final int right = left + mDivider.getIntrinsicWidth();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        if (mOrientation == VERTICAL_LIST) {
            outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
        } else if(mOrientation == HORIZONTAL_LIST) {
            outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
        } else {
            outRect.set(0, 0, mDivider.getIntrinsicWidth(), mDivider.getIntrinsicHeight());
        }
    }
}

- Nauman Zubair

---

如果网格的行大小不同，则无法正常工作。 - android developer

Answer 4

这是我在 Kotlin 中的实现。我修改了其他答案的代码，以便为完全跨度的项目也显示分隔符。

import android.graphics.Rect
import android.view.View
import androidx.recyclerview.widget.GridLayoutManager
import androidx.recyclerview.widget.RecyclerView

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

    override fun getItemOffsets(
        outRect: Rect,
        view: View,
        parent: RecyclerView,
        state: RecyclerView.State
    ) {
        val position = parent.getChildAdapterPosition(view)

        val totalSpanCount = getTotalSpanCount(parent)
        val spanSize = getItemSpanSize(parent, position)

        outRect.top = if (isInTheFirstRow(position, totalSpanCount)) 0 else spacing
        outRect.left = if (isFirstInRow(position, totalSpanCount, spanSize)) 0 else spacing / 2
        outRect.right = if (isLastInRow(position, totalSpanCount, spanSize)) 0 else spacing / 2
        outRect.bottom = 0
    }

    private fun isInTheFirstRow(position: Int, totalSpanCount: Int): Boolean =
        position < totalSpanCount

    private fun isFirstInRow(position: Int, totalSpanCount: Int, spanSize: Int): Boolean =
        if (totalSpanCount != spanSize) {
            position % totalSpanCount == 0
        } else true

    private fun isLastInRow(position: Int, totalSpanCount: Int, spanSize: Int): Boolean =
        isFirstInRow(position + 1, totalSpanCount, spanSize)

    private fun getTotalSpanCount(parent: RecyclerView): Int =
        (parent.layoutManager as? GridLayoutManager)?.spanCount ?: 1

    private fun getItemSpanSize(parent: RecyclerView, position: Int): Int =
        (parent.layoutManager as? GridLayoutManager)?.spanSizeLookup?.getSpanSize(position) ?: 1
}

结果：

- Micer

---

如果在0位置有一个完整跨度的项目怎么办？定义的方法isInTheFirstRow，isFirstInRow，isLastInRow似乎不太通用。它是仅针对您在图像中显示的特定用例还是通用的？ - rd7773

它应该是通用的，但你说得对，我认为0位置的完全跨度项目没有被覆盖。不过我没有尝试过。 - Micer

另外，您如何设置这些装饰线的自定义颜色？不是针对应用程序中的所有分隔符（android：listDivider），而仅针对此RecyclerView？有任何想法吗？ - rd7773

你可以在RecyclerView的样式中添加<item name="android:listDivider">@drawable/divider_grid</item>。 - Micer

这将适用于应用程序中的所有分隔符，我们只需要针对特定的装饰器应用。 - rd7773

Answer 5

还有一种对我有效的简单解决方案，希望它能够有用。

class GridItemDecorator(val context: Context, private val spacingDp: Int, private val mGridSize: Int) : RecyclerView.ItemDecoration() {

    override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {

        val resources = context.resources
        val spacingPx = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, spacingDp.toFloat(), resources.displayMetrics)

        val bit = if (spacingPx > mGridSize) Math.round(spacingPx / mGridSize) else 1
        val itemPosition = (view.layoutParams as RecyclerView.LayoutParams).viewAdapterPosition

        outRect.top = if (itemPosition < mGridSize) 0 else  bit * mGridSize
        outRect.bottom = 0

        val rowPosition = itemPosition % mGridSize
        outRect.left = rowPosition * bit
        outRect.right = (mGridSize - rowPosition - 1) * bit

    }
}

- AlexKost

Answer 6

如果您使用标题，则使用此选项。

要隐藏标题分隔符，请将skipHeaderDivider设置为false，否则设置为true。

class GridDividerItemDecoration : ItemDecoration() {

    var skipHeaderDivider = true

    private var divider: Drawable? = null

    private val bounds = Rect()

    private var spacing = 0

    fun setDrawable(drawable: Drawable) {
        divider = drawable
        divider?.intrinsicHeight?.let { spacing = it }
    }

    override fun onDraw(canvas: Canvas, parent: RecyclerView, state: RecyclerView.State) {
        canvas.save()
        val childCount = parent.childCount
        for (i in 0 until childCount) {
            val child = parent.getChildAt(i)
            parent.layoutManager?.getDecoratedBoundsWithMargins(child, bounds)

            val right: Int = bounds.right + child.translationX.roundToInt()
            val left: Int = bounds.left - child.translationX.roundToInt()
            val bottom: Int = bounds.bottom + child.translationY.roundToInt()
            val top: Int = bounds.top - child.translationY.roundToInt()

            divider?.setBounds(left, top, right, bottom)
            divider?.draw(canvas)
        }
        canvas.restore()
    }

    override fun getItemOffsets(
        outRect: Rect,
        view: View,
        parent: RecyclerView,
        state: RecyclerView.State
    ) {
        val gridLayoutManager = parent.layoutManager as? GridLayoutManager ?: return
        val position = gridLayoutManager.getPosition(view)
        if (position < 0) return
        val spanCount = gridLayoutManager.spanCount
        val positionalSpanSize = gridLayoutManager.spanSizeLookup.getSpanSize(position)

        if (skipHeaderDivider && positionalSpanSize == spanCount) return

        val itemCount = gridLayoutManager.itemCount

        val onBottom = position >= itemCount - spanCount
        var nextHeader = false

        run loop@{
            for (i in 1..spanCount) {
                val nextSpanSize = gridLayoutManager.spanSizeLookup.getSpanSize(position + i)
                if (nextSpanSize == spanCount) {
                    nextHeader = true
                    return@loop
                }
            }
        }

        outRect.top = spacing
        outRect.left = 0
        outRect.right = spacing
        outRect.bottom = if (nextHeader || onBottom) spacing else 0
    }
}

- Yeldar Nurpeissov

Answer 7

这是我的版本。基于Nicolay's answer，但改进为适用于三个或更多图像的网格，并使用dp单位进行间距。(他的版本在有超过2张图片时不能给出相等大小的图片/间距。)

注意：计算每个图像间距的逻辑比大多数答案所考虑的仅仅将间距除以二更为复杂。

/**
 * Class to add INTERNAL SPACING to a grid of items. Only works for a grid with 3 columns or more.
 */
class PhotoSpaceDecoration extends RecyclerView.ItemDecoration {
    private final int spacingWidthPx;

    /**
     * Initialise with the with of the spacer in dp
     *
     * @param spacingWidthDp this will be divided between elements and applied as a space on each side
     *                       NB: for proper alignment this must be divisible by 2 and by the number of columns
     */
    public PhotoSpaceDecoration(Context context, int spacingWidthDp) {
        // Convert DP to pixels
        this.spacingWidthPx = (int)TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, spacingWidthDp,
                                                             context.getResources().getDisplayMetrics());
    }

    /**
     * @param index           a 0 indexed value of the current item
     * @param numberOfColumns
     * @return a 0 indexed Point with the x & y location of the item in the grid
     */
    private Point getItemXY(int index, int numberOfColumns) {
        int x = index % numberOfColumns;
        int y = index / numberOfColumns; // NB: integer division
        return new Point(x, y);
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        final int position = parent.getChildAdapterPosition(view);
        final int columns = getTotalSpanCount(parent);
        final int rows = (int) Math.ceil(parent.getChildCount() / (double) columns); // NB: NOT integer division
        int spanSize = getItemSpanSize(parent, position);
        if (columns == spanSize) {
            return;
        }

        Point point = getItemXY(position, columns);
        int firstMargin = spacingWidthPx * (columns - 1) / columns;
        int secondMargin = spacingWidthPx - firstMargin;
        int middleMargin = spacingWidthPx / 2;

        if (point.x == 0) { // first column
            outRect.left = 0;
            outRect.right = firstMargin;
        } else if (point.x == 1) { // second column
            outRect.left = secondMargin;
            outRect.right = rows > 3 ? middleMargin : secondMargin;
        } else if (point.x - columns == -2) { // penultimate column
            outRect.left = rows > 3 ? middleMargin : secondMargin;
            outRect.right = secondMargin;
        } else if (point.x - columns == -1) { // last column
            outRect.left = firstMargin;
            outRect.right = 0;
        } else { // middle columns
            outRect.left = middleMargin;
            outRect.right = middleMargin;
        }

        if (point.y == 0) { // first row
            outRect.top = 0;
            outRect.bottom = firstMargin;
        } else if (point.y == 1) { // second row
            outRect.top = secondMargin;
            outRect.bottom = rows > 3 ? middleMargin : secondMargin;
        } else if (point.y - rows == -2) { // penultimate row
            outRect.top = rows > 3 ? middleMargin : secondMargin;
            outRect.bottom = secondMargin;
        } else if (point.y - rows == -1) { // last row
            outRect.top = firstMargin;
            outRect.bottom = 0;
        } else { // middle rows
            outRect.top = middleMargin;
            outRect.bottom = middleMargin;
        }
    }

    private int getTotalSpanCount(RecyclerView parent) {
        final RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        return layoutManager instanceof GridLayoutManager ? ((GridLayoutManager) layoutManager).getSpanCount() : 1;
    }

    private int getItemSpanSize(RecyclerView parent, int position) {
        final RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        return layoutManager instanceof GridLayoutManager ? ((GridLayoutManager) layoutManager).getSpanSizeLookup()
                                                                                               .getSpanSize(
                                                                                                       position) : 1;
    }
}

这适用于从Activity.onCreate()应用到回收视图，如下所示。

photosRecyclerView.addItemDecoration(new PhotoSpaceDecoration(this, 6));

例子：

- Inti

Answer 8

以下是我自定义的Kotlin类，允许在网格单元之间实现等距离间距：

class GridItemOffsetDecoration(private val spanCount: Int, private var mItemOffset: Int) : ItemDecoration() {

override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView,
                            state: RecyclerView.State) {
    val position = parent.getChildAdapterPosition(view)

    if (position < spanCount) {
        if (position % 2 == 0) { // left grid
            outRect.set(0, mItemOffset, mItemOffset / 2, mItemOffset / 2)
        } else { // right grid
            outRect.set(mItemOffset / 2, mItemOffset, 0, mItemOffset / 2)
        }

    } else if (position % 2 == 0) { // left grid
        outRect.set(0, mItemOffset / 2, mItemOffset, mItemOffset / 2)

    } else if (position % 2 == 1) { // right grid
        outRect.set(mItemOffset / 2, mItemOffset / 2, 0, mItemOffset / 2)

    } else {
        if (position % 2 == 0) { // left grid
            outRect.set(0, mItemOffset / 2, mItemOffset, mItemOffset)
        } else { // right grid
            outRect.set(mItemOffset / 2, mItemOffset / 2, 0, mItemOffset)
        }
    }
}

}

要将其添加为RecyclerView中的项目装饰器，请添加以下行：

/*spanCount is the number of grids, for instance, (2 = 2*2 grid, 3 = 3*3)*/
binding.rvActiveChallenges.addItemDecoration(GridItemOffsetDecoration(2, resources.getDimensionPixelSize(R.dimen._10dp)))

- Siddharth Thakkar

Answer 9

  @BindingAdapter({"bind:adapter"})
    public static void bind(RecyclerView view, RecyclerView.Adapter<BaseViewHolder> adapter) {
        view.setLayoutManager(new GridLayoutManager(view.getContext(), 3));
        view.addItemDecoration(new SpacesItemDecorationGrid(view.getContext(), 4, 3));
        view.setItemAnimator(new DefaultItemAnimator());
        view.setAdapter(adapter);
    }


public class SpacesItemDecorationGrid extends RecyclerView.ItemDecoration {

    private int mSizeGridSpacingPx;
    private int mGridSize;
    private boolean mNeedLeftSpacing = false;

    /**
     * @param gridSpacingPx
     * @param gridSize
     */
    SpacesItemDecorationGrid(Context context, int gridSpacingPx, int gridSize) {
        mSizeGridSpacingPx = (int) Util.convertDpToPixel(gridSpacingPx, context);
        mGridSize = gridSize;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        int frameWidth = (int) ((parent.getWidth() - (float) mSizeGridSpacingPx * (mGridSize - 1)) / mGridSize);
        int padding = parent.getWidth() / mGridSize - frameWidth;
        int itemPosition = ((RecyclerView.LayoutParams) view.getLayoutParams()).getViewAdapterPosition();
        int itemCount = parent.getAdapter().getItemCount() - mGridSize;


   /*     if (itemPosition < mGridSize) {
            outRect.top = mSizeGridSpacingPx;
        } else {
                   outRect.top = mSizeGridSpacingPx;
        }*/
        outRect.top = mSizeGridSpacingPx;
        if (itemPosition % mGridSize == 0) {
            outRect.left = mSizeGridSpacingPx;
            outRect.right = padding;
            mNeedLeftSpacing = true;
        } else if ((itemPosition + 1) % mGridSize == 0) {
            mNeedLeftSpacing = false;
            outRect.right = mSizeGridSpacingPx;
            outRect.left = padding;
        } else if (mNeedLeftSpacing) {
            mNeedLeftSpacing = false;
            outRect.left = mSizeGridSpacingPx - padding;
            if ((itemPosition + 2) % mGridSize == 0) {
                outRect.right = mSizeGridSpacingPx - padding;
            } else {
                outRect.right = mSizeGridSpacingPx / 2;
            }
        } else if ((itemPosition + 2) % mGridSize == 0) {
            mNeedLeftSpacing = false;
            outRect.left = mSizeGridSpacingPx / 2;
            outRect.right = mSizeGridSpacingPx - padding;
        } else {
            mNeedLeftSpacing = false;
            outRect.left = mSizeGridSpacingPx / 2;
            outRect.right = mSizeGridSpacingPx / 2;
        }
        if (itemPosition > itemCount) {
            outRect.bottom = mSizeGridSpacingPx;
        } else {
            outRect.bottom = 0;
        }

    }

}

- Dhaval Joshi

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请考虑添加一些解释代码的说明。仅有代码的答案在技术上可能回答了问题，但不太可能对其他遇到类似问题的用户有用。 - Peter Hall

Answer 10

你可以尝试我的解决方案。如果您想要列表视图或网格视图，这个方案非常灵活。

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

    override fun getItemOffsets(
        outRect: Rect,
        view: View,
        parent: RecyclerView,
        state: RecyclerView.State
    ) {
        val position = parent.getChildAdapterPosition(view)

        val totalSpanCount = getTotalSpanCount(parent)
        val spanSize = getItemSpanSize(parent, position)

        // if list view span == 1
        if (totalSpanCount == 1) {
            if (position == 0) {
                outRect.top = 10.dp
            } else {
                outRect.top = spacing
            }
            outRect.left = spacing
            outRect.right = spacing
            if (position == parent.adapter?.itemCount?.minus(1)) {
                outRect.bottom = spacing
            }
        } else { // if grid view span >= 2
            outRect.top = if (isInTheFirstRow(position, totalSpanCount)) 0 else spacing
            outRect.left = if (isFirstInRow(position, totalSpanCount, spanSize)) 0 else spacing / 2
            outRect.right = if (isLastInRow(position, totalSpanCount, spanSize)) 0 else spacing / 2
            outRect.bottom = 0

            when {
                position % 2 == 0 -> {
                    outRect.left = spacing
                }
                else -> {
                    outRect.right = spacing
                }
            }
            outRect.top = 10.dp
            if (position >= parent.adapter?.itemCount?.minus(2) ?: 0) { // minus(2) -> 2 is span count
                outRect.bottom = spacing
            }
        }
    }

    private fun isInTheFirstRow(position: Int, totalSpanCount: Int): Boolean =
        position < totalSpanCount

    private fun isFirstInRow(position: Int, totalSpanCount: Int, spanSize: Int): Boolean =
        if (totalSpanCount != spanSize) {
            position % totalSpanCount == 0
        } else true

    private fun isLastInRow(position: Int, totalSpanCount: Int, spanSize: Int): Boolean =
        isFirstInRow(position + 1, totalSpanCount, spanSize)

    private fun getTotalSpanCount(parent: RecyclerView): Int =
        (parent.layoutManager as? GridLayoutManager)?.spanCount ?: 1

    private fun getItemSpanSize(parent: RecyclerView, position: Int): Int =
        (parent.layoutManager as? GridLayoutManager)?.spanSizeLookup?.getSpanSize(position) ?: 1
}

注意：这是针对 span 计数为 2 的特殊情况。

- ghozi mahdi

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目前你的回答不够清晰，请编辑并添加更多细节以帮助其他人理解它如何回答所提出的问题。你可以在帮助中心找到有关如何撰写好答案的更多信息。 - Community

不鼓励只提供代码的答案，因此请在您的答案中添加一些解释。虽然代码可能没问题，但如果您能解释它是如何工作的，如何回答问题以及与所有现有答案的方法有何不同，那将更有帮助。 - skomisa