2016年10月更新

在v25.0.0支持库中，终于有了基本水平和垂直分隔符的默认实现!

DividerItemDecoration

RecyclerView没有为绘制列表分隔符提供一个简单的接口。但实际上它为我们提供了更灵活的 划分隔线的方法。

我们使用RecyclerView。用分隔线或任何你想要的东西来装饰RecyclerView的瓷砖。这也是为什么它被称为ItemDecoration。

如《材料设计指南》所述:

分隔符位于贴图的基线内。

所以如果你想遵循材料设计指南，你不需要额外的空间来画分隔线。把它们画在瓷砖上。然而，你有权利做任何你想做的事。所以我实现了一个让你能够设置嵌入以及在瓷砖上/下面绘制的功能。

public class InsetDivider extends RecyclerView.ItemDecoration {

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

    private Paint mPaint;
    // in pixel
    private int mDividerHeight;
    // left inset for vertical list, top inset for horizontal list
    private int mFirstInset;
    // right inset for vertical list, bottom inset for horizontal list
    private int mSecondInset;
    private int mColor;
    private int mOrientation;
    // set it to true to draw divider on the tile, or false to draw beside the tile.
    // if you set it to false and have inset at the same time, you may see the background of
    // the parent of RecyclerView.
    private boolean mOverlay;

    private InsetDivider() {
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mPaint.setStyle(Paint.Style.FILL);
    }

    public int getDividerHeight() {
        return mDividerHeight;
    }

    public void setDividerHeight(int dividerHeight) {
        this.mDividerHeight = dividerHeight;
    }

    public int getFirstInset() {
        return mFirstInset;
    }

    public void setFirstInset(int firstInset) {
        this.mFirstInset = firstInset;
    }

    public int getSecondInset() {
        return mSecondInset;
    }

    public void setSecondInset(int secondInset) {
        this.mSecondInset = secondInset;
    }

    public int getColor() {
        return mColor;
    }

    public void setColor(int color) {
        this.mColor = color;
        mPaint.setColor(color);
    }

    public int getOrientation() {
        return mOrientation;
    }

    public void setOrientation(int orientation) {
        this.mOrientation = orientation;
    }

    public boolean getOverlay() {
        return mOverlay;
    }

    public void setOverlay(boolean overlay) {
        this.mOverlay = overlay;
    }

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

    protected void drawVertical(Canvas c, RecyclerView parent) {
        final int left = parent.getPaddingLeft() + mFirstInset;
        final int right = parent.getWidth() - parent.getPaddingRight() - mSecondInset;
        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            if (parent.getChildAdapterPosition(child) == (parent.getAdapter().getItemCount() - 1)) {
                continue;
            }
            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
            final int bottom;
            final int top;
            if (mOverlay) {
                bottom = child.getBottom() + params.bottomMargin + Math.round(ViewCompat.getTranslationY(child));
                top = bottom - mDividerHeight;
            } else {
                top = child.getBottom() + params.bottomMargin + Math.round(ViewCompat.getTranslationY(child));
                bottom = top + mDividerHeight;
            }
            c.drawRect(left, top, right, bottom, mPaint);
        }
    }

    protected void drawHorizontal(Canvas c, RecyclerView parent) {
        final int top = parent.getPaddingTop() + mFirstInset;
        final int bottom = parent.getHeight() - parent.getPaddingBottom() - mSecondInset;
        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            if (parent.getChildAdapterPosition(child) == (parent.getAdapter().getItemCount() - 1)) {
                continue;
            }
            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                .getLayoutParams();
            final int right;
            final int left;
            if (mOverlay) {
                right = child.getRight() + params.rightMargin + Math.round(ViewCompat.getTranslationX(child));
                left = right - mDividerHeight;
            } else {
                left = child.getRight() + params.rightMargin + Math.round(ViewCompat.getTranslationX(child));
                right = left + mDividerHeight;
            }
            c.drawRect(left, top, right, bottom, mPaint);
        }
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        if (mOverlay) {
            super.getItemOffsets(outRect, view, parent, state);
            return;
        }

        if (mOrientation == VERTICAL_LIST) {
            outRect.set(0, 0, 0, mDividerHeight);
        } else {
            outRect.set(0, 0, mDividerHeight, 0);
        }
    }

    /**
     * Handy builder for creating {@link InsetDivider} instance.
     */
    public static class Builder {

        private Context mContext;
        private int mDividerHeight;
        private int mFirstInset;
        private int mSecondInset;
        private int mColor;
        private int mOrientation;
        private boolean mOverlay = true; // set default to true to follow Material Design Guidelines

        public Builder(Context context) {
            mContext = context;
        }

        public Builder dividerHeight(int dividerHeight) {
            mDividerHeight = dividerHeight;
            return this;
        }

        public Builder insets(int firstInset, int secondInset) {
            mFirstInset = firstInset;
            mSecondInset = secondInset;
            return this;
        }

        public Builder color(@ColorInt int color) {
            mColor = color;
            return this;
        }

        public Builder orientation(int orientation) {
            mOrientation = orientation;
            return this;
        }

        public Builder overlay(boolean overlay) {
            mOverlay = overlay;
            return this;
        }

        public InsetDivider build() {
            InsetDivider insetDivider = new InsetDivider();

            if (mDividerHeight == 0) {
                // Set default divider height to 1dp.
                 insetDivider.setDividerHeight(mContext.getResources().getDimensionPixelSize(R.dimen.divider_height));
            } else if (mDividerHeight > 0) {
                insetDivider.setDividerHeight(mDividerHeight);
            } else {
                throw new IllegalArgumentException("Divider's height can't be negative.");
            }

            insetDivider.setFirstInset(mFirstInset < 0 ? 0 : mFirstInset);
            insetDivider.setSecondInset(mSecondInset < 0 ? 0 : mSecondInset);

            if (mColor == 0) {
                throw new IllegalArgumentException("Don't forget to set color");
            } else {
                insetDivider.setColor(mColor);
            }

            if (mOrientation != InsetDivider.HORIZONTAL_LIST && mOrientation != InsetDivider.VERTICAL_LIST) {
                throw new IllegalArgumentException("Invalid orientation");
            } else {
                insetDivider.setOrientation(mOrientation);
            }

            insetDivider.setOverlay(mOverlay);

            return insetDivider;
        }
    }
}

你可以这样使用它:

ItemDecoration divider = new InsetDivider.Builder(this)
                            .orientation(InsetDivider.VERTICAL_LIST)
                            .dividerHeight(getResources().getDimensionPixelSize(R.dimen.divider_height))
                            .color(getResources().getColor(R.color.colorAccent))
                            .insets(getResources().getDimensionPixelSize(R.dimen.divider_inset), 0)
                            .overlay(true)
                            .build();

RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.addItemDecoration(divider);

我还写了一个关于如何实现ItemDecoration以及如何使用它们的演示应用程序。你可以查看我的GitHub存储库Dividers-For-RecyclerView。它有三个实现:

下隔板 叠加分隔器 插入分隔器

以下是我的偷懒方法，但它很有效: 将CardView包装在一个布局中，并在父布局上设置一个填充/边距来模拟分隔符，并强制将普通分隔符设置为null。

文件list_item.xml

<LinearLayout
    android:id="@+id/entry_item_layout_container"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:paddingBottom="<divider_size>" > // This is the divider
    <CardView
        android:layout_width="<width_size>"
        android:layout_height="<height_size>">
        ...
    </CardView>
</LinearLayout

文件list.xml

<RecyclerView
    android:divider="@null"
    android:layout_width="<width_size>"
    android:layout_height="<height_size>"
    ...
/>

请注意一下Alex Fu在GitHub上的这个文件: 链接

它是“直接从支持演示中提取”的diveritemdecoration .java示例文件。

在我的项目中导入这个文件后，我能够很好地获得分隔线，并将其作为项目装饰添加到回收器视图。

下面是我的onCreateView在我的片段中包含Recyclerview的样子:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_recycler_view, container, false);

    mRecyclerView = (RecyclerView) rootView.findViewById(R.id.my_recycler_view);
    mRecyclerView.addItemDecoration(new DividerItemDecoration(getActivity(), DividerItemDecoration.VERTICAL));

    mRecyclerView.setHasFixedSize(true);
    mLayoutManager = new LinearLayoutManager(getActivity());
    mRecyclerView.setLayoutManager(mLayoutManager);
    mRecyclerView.setItemAnimator(new DefaultItemAnimator());

    return rootView;
}

我确信可以做额外的造型，但这只是一个起点。：）

实现它自己的RecyclerView版本。ItemDecoration

public class SpacingItemDecoration extends RecyclerView.ItemDecoration {
    private int spacingPx;
    private boolean addStartSpacing;
    private boolean addEndSpacing;

    public SpacingItemDecoration(int spacingPx) {
        this(spacingPx, false, false);
    }

    public SpacingItemDecoration(int spacingPx, boolean addStartSpacing, boolean addEndSpacing) {
        this.spacingPx = spacingPx;
        this.addStartSpacing = addStartSpacing;
        this.addEndSpacing = addEndSpacing;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        if (spacingPx <= 0) {
            return;
        }

        if (addStartSpacing && parent.getChildLayoutPosition(view) < 1 || parent.getChildLayoutPosition(view) >= 1) {
            if (getOrientation(parent) == LinearLayoutManager.VERTICAL) {
                outRect.top = spacingPx;
            } else {
                outRect.left = spacingPx;
            }
        }

        if (addEndSpacing && parent.getChildAdapterPosition(view) == getTotalItemCount(parent) - 1) {
            if (getOrientation(parent) == LinearLayoutManager.VERTICAL) {
                outRect.bottom = spacingPx;
            } else {
                outRect.right = spacingPx;
            }
        }
    }

    private int getTotalItemCount(RecyclerView parent) {
        return parent.getAdapter().getItemCount();
    }

    private int getOrientation(RecyclerView parent) {
        if (parent.getLayoutManager() instanceof LinearLayoutManager) {
            return ((LinearLayoutManager) parent.getLayoutManager()).getOrientation();
        } else {
            throw new IllegalStateException("SpacingItemDecoration can only be used with a LinearLayoutManager.");
        }
    }
}

为视图添加边距。这对我很管用。

android:layout_marginTop="10dp"

如果你只是想在XML中添加相等的间距，只需在RecyclerView中设置padding，并在你膨胀到RecyclerView中的项目中设置等量的layoutMargin，并让背景颜色决定间距颜色。