如何在几个项目之后添加一个分隔符来分隔 RecyclerView 中的组？

Question

我有一个问题。我想在我的 Recyclerview 导航抽屉中使用一个分隔线。我怎样才能做到这一点？现在我有一个 DividerItemDecoration.java，每个项目后面都有一个分隔符，这不是我想要的。我想在特定项目之后设置一个分隔符。这是 DividerItemDecoration.java 代码：

package com.***********.************;

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;

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) {
        throw new IllegalArgumentException("invalid orientation");
    }
    mOrientation = orientation;
}

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

public void drawVertical(Canvas c, RecyclerView parent) {
    final int left = parent.getPaddingLeft();
    final int right = parent.getWidth() - parent.getPaddingRight();

    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 top = child.getBottom() + params.bottomMargin;
        final int bottom = top + mDivider.getIntrinsicHeight();
        mDivider.setBounds(left, top, right, bottom);
        mDivider.draw(c);
    }
}

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;
        final int right = left + mDivider.getIntrinsicHeight();
        mDivider.setBounds(left, top, right, bottom);
        mDivider.draw(c);
    }
}

@Override
public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) {
    if (mOrientation == VERTICAL_LIST) {
        outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
    } else {
        outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
    }
}

这是 NavigatonDrawerFragment.java 的 onCreateView：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_navigation_drawer, container, false);
    mDrawerList = (RecyclerView) view.findViewById(R.id.drawerList);
    LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity());
    layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
    mDrawerList.setLayoutManager(layoutManager);
    mDrawerList.setHasFixedSize(true);
    mDrawerList.addItemDecoration(new DividerItemDecoration(getActivity(), DividerItemDecoration.VERTICAL_LIST));
    mDrawerList.setItemAnimator(new DefaultItemAnimator());

    final List<NavigationItem> navigationItems = getMenu();
    NavigationDrawerAdapter adapter = new NavigationDrawerAdapter(navigationItems);
    adapter.setNavigationDrawerCallbacks(this);
    mDrawerList.setAdapter(adapter);
    selectItem(mCurrentSelectedPosition);
    return view;
}

Answer 1

简单的解决方案https://pastebin.com/4J7sPaCF

public class SingleDividerDecoration extends DividerItemDecoration {

    private final int height;
    private int position = -1;

    public SingleDividerDecoration(Context context, @DrawableRes int dividerId) {
        super(context, LinearLayout.VERTICAL);
        Drawable divider = ContextCompat.getDrawable(context, dividerId);
        this.height = divider.getIntrinsicHeight();
        setDrawable(divider);
    }

    public void setPosition(int position) {
        this.position = position;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        int viewPosition = parent.getChildAdapterPosition(view);
        int dividerHeight = viewPosition == position ? height : 0;
        outRect.set(0, 0, 0, dividerHeight);
    }
}