在RecyclerView中封装了ViewHolder的回收复用，将ViewHolder标准化；通过LayoutManager设置布局显示方式；通过ItemDecoration设置布局分割线；通过ItemAnimator设置添加和删除item的动画效果；RecyclerView本身是不提供点击、长按事件。

一、RecyclerView使用

（1）导入支持的库

dependencies {
    compile 'com.android.support:recyclerview-v7:28.0.1'
}

（2）布局文件

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</RelativeLayout>

（3）布局管理器

• LinearLayoutManager：线性布局管理器

//orientation：设置布局方向
//reverseLayout：是否设置逆向布局
LinearLayoutManager(context)
LinearLayoutManager(context, orientation, reverseLayout)

• GridLayoutManager：网格布局管理器

//spanCount：设置行数或列数
//orientation：设置布局方向
//reverseLayout：是否设置逆向布局
GridLayoutManager(context, spanCount)
GridLayoutManager(context, spanCount,orientation, reverseLayout)

• StaggeredGridLayoutManager：瀑布流布局管理器

//spanCount：设置行数或列数
//orientation：设置布局方向
StaggeredGridLayoutManager(spanCount, orientation)

（4）adapter中的代码实现

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {

    private Context context;
    private List<String> list;
    private LayoutInflater inflater;
    private MyAdapter.MyItemClickListener mItemClickListener;

    public MyAdapter(Context context, List<String> list) {
        this.inflater = LayoutInflater.from(context);
        this.list = list;
        this.context = context;
    }

    //创建ViewHolder
    @Override
    public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = inflater.inflate(R.layout.layout_item, parent, false);
        MyAdapter.ViewHolder viewHolder = new MyAdapter.ViewHolder(view, mItemClickListener);
        return viewHolder;
    }

    //向item中添加数据
    @Override
    public void onBindViewHolder(MyAdapter.ViewHolder holder, int position) {
        holder.tv_name.setText(list.get(position));
    }

    //返回item个数
    @Override
    public int getItemCount() {
        return list.size();
    }

    //填充视图、设置点击事件。
    public static class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        public MyAdapter.MyItemClickListener myItemClickListener;
        private TextView tv_name;

        public ViewHolder(View itemView, MyAdapter.MyItemClickListener myItemClickListener) {
            super(itemView);
            this.myItemClickListener = myItemClickListener;
            itemView.setOnClickListener(this);
            tv_name = itemView.findViewById(R.id.tv_name);
        }

        @Override
        public void onClick(View v) {
            if (myItemClickListener != null) {
                myItemClickListener.onItemClick(v, getPosition());
            }
        }
    }

    public interface MyItemClickListener {
        void onItemClick(View view, int position);
    }

    //通过实现接口处理点击事件
    public void setItemClickListener(MyAdapter.MyItemClickListener myItemClickListener) {
        this.mItemClickListener = myItemClickListener;
    }

    //添加数据
    public void onItemAdd(int position) {
        list.add(position, "position");
        notifyItemInserted(position);
    }

    //移除数据
    public void onItemRemove(int position) {
        list.remove(position);
        notifyItemRemoved(position);
    }

    //移动时交换位置
    public void onItemMove(int fromPosition, int toPosition) {
        Collections.swap(list, fromPosition, toPosition);
    }
}

（5）代码中实现

recyclerView = findViewById(R.id.recycler_view);
LayoutManager layoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, true);
recyclerView.setLayoutManager(layoutManager);//设置管理器
recyclerView.setAdapter(adapter)//添加adapter
recyclerView.setItemAnimator(new DefaultItemAnimator());//设置删除、添加动画
recyclerView.addItemDecoration(new DividerItemDecoration(getActivity(), 
  DividerItemDecoration.HORIZONTAL_LIST));//设置分割线

adapter.onItemRemove(1);//删除数据
adapter.onItemAdd(0);//添加数据
recyclerView.scrollToPosition(0);//解决添加无动画

二、加载不同布局的item

• 修改adapter中的代码

public class MyAdapter extends RecyclerView.Adapter {

    private Context context;
    private List<Data> list;
    private LayoutInflater inflater;
    private MyAdapter.MyItemClickListener mItemClickListener;

    public MyAdapter(Context context, List<String> list){
        this.inflater = LayoutInflater.from(context);
        this.list = list;
        this.context = context;
    }

    //创建ViewHolder
    @Override
    public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        switch (viewType){
            case 0:
                View view_0 = inflater.inflate(R.layout.layout_item_0, parent, false);
                ViewHolder0 viewHolder0 = new ViewHolder0(view_0, mItemClickListener);
                return viewHolder0;
            case 1:
                View view = inflater.inflate(R.layout.layout_item_1, parent, false);
                ViewHolder1 viewHolder1 = new ViewHolder1(view_1, mItemClickListener);
                return viewHolder1;
        }
        return null;
    }

    //向item中添加数据
    @Override
    public void onBindViewHolder(MyAdapter.ViewHolder holder, int position) {
        int type = list.get(position).getType();
        switch (type){
            case 0:
                ViewHolder0 holder0= (ViewHolder0) holder;
                holder0.tv_name.setText(list.get(position).name);
                break;
            case 1:
                ViewHolder1 holder1= (ViewHolder1) holder;
                holder1.tv_name.setText(list.get(position).name);
                break;
        }
    }

    //返回item个数
    @Override
    public int getItemCount() {
        return list.size();
    }

    //返回viewHolder的类型
    @Override
    public int getItemViewType(int position) {
        return list.get(position).getType;
    }

    //填充视图、设置点击事件。
    public static class ViewHolder0 extends RecyclerView.ViewHolder implements View.OnClickListener {
        public MyAdapter.MyItemClickListener myItemClickListener;
        private TextView tv_name;
        public ViewHolder0(View itemView, MyAdapter.MyItemClickListener myItemClickListener) {
            super(itemView);
            this.myItemClickListener = myItemClickListener;
            itemView.setOnClickListener(this);
            tv_name = itemView.findViewById(R.id.tv_name);
        }

        @Override
        public void onClick(View v) {
            if (myItemClickListener != null) {
                myItemClickListener.onItemClick(v, getPosition());
            }
        }
    }

    public static class ViewHolder1 extends RecyclerView.ViewHolder implements View.OnClickListener {
        public MyAdapter.MyItemClickListener myItemClickListener;
        private TextView tv_name;
        public ViewHolder1(View itemView, MyAdapter.MyItemClickListener myItemClickListener) {
            super(itemView);
            this.myItemClickListener = myItemClickListener;
            itemView.setOnClickListener(this);
            tv_name = itemView.findViewById(R.id.tv_name);
        }

        @Override
        public void onClick(View v) {
            if (myItemClickListener != null) {
                myItemClickListener.onItemClick(v, getPosition());
            }
        }
    }

    public interface MyItemClickListener {
        void onItemClick(View view, int position);
    }

    //通过实现接口处理点击事件
    public void setItemClickListener(MyAdapter.MyItemClickListener myItemClickListener) {
        this.mItemClickListener = myItemClickListener;
    }
}

三、侧滑删除、长按拖动

（1）自定义的类继承ItemTouchHelper.Callback抽象类

public class RecyclerItemTouchCallback extends ItemTouchHelper.Callback {
    private MyAdapter adapter;
    private boolean isLongPressDragEnabled = true;
    private boolean isItemViewSwipeEnabled = true;

    public RecyclerItemTouchCallback(MyAdapter adapter) {
        this.adapter = adapter;
    }

    public RecyclerItemTouchCallback(MyAdapter adapter, boolean isLongPressDragEnabled, boolean isItemViewSwipeEnabled) {
        this.adapter = adapter;
        this.isLongPressDragEnabled = isLongPressDragEnabled;
        this.isItemViewSwipeEnabled = isItemViewSwipeEnabled;
    }

    @Override
    public int getMovementFlags(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) {
        int dragFlags, swipeFlags;
        RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
        if (layoutManager instanceof GridLayoutManager || layoutManager instanceof StaggeredGridLayoutManager) {
            //设置拖动的方向
            dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN | ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT;
            swipeFlags = 0;
        } else {
            //设置拖动的方向
            dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN;
            //表示滑动的方向
            swipeFlags = ItemTouchHelper.START | ItemTouchHelper.END;
        }
        //值传0，表示不支持该功能
        return makeMovementFlags(dragFlags, swipeFlags);
    }

    //拖拽过程中调用
    @Override
    public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target) {
        //判断viewType是否相同
        int fromPosition = viewHolder.getAdapterPosition();
        int toPosition = target.getAdapterPosition();
        if (!isLongPressDragEnabled && toPosition == 0) {
            return false;
        }
        if (fromPosition < toPosition) {
            //途中所有的item位置都要移动
            for (int i = fromPosition; i < toPosition; i++) {
                //调用adapter方法移动数据
                adapter.onItemMove(i, i + 1);
            }
        } else {
            for (int i = fromPosition; i > toPosition; i--) {
                //调用adapter方法移动数据
                adapter.onItemMove(i, i - 1);
            }
        }
        adapter.notifyItemMoved(fromPosition, toPosition);
        return true;
    }

    //滑动移除的方法
    @Override
    public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction) {
        //调用adapter删除数据并更新
        adapter.onItemRemove(viewHolder.getAdapterPosition());
    }

    //给选中的item添加背景颜色
    @Override
    public void onSelectedChanged(@Nullable RecyclerView.ViewHolder viewHolder, int actionState) {
        if (actionState == ItemTouchHelper.ACTION_STATE_DRAG) {
            //拖拽状态背景颜色
            assert viewHolder != null;
            viewHolder.itemView.setBackgroundColor(Color.BLUE);
        } else if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
            //滑动删除状态背景颜色
            assert viewHolder != null;
            viewHolder.itemView.setBackgroundColor(Color.RED);
        }
        super.onSelectedChanged(viewHolder, actionState);
    }

    //恢复选中item背景
    @Override
    public void clearView(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) {
        viewHolder.itemView.setBackgroundColor(Color.TRANSPARENT);
        super.clearView(recyclerView, viewHolder);
    }

    //是否支持长按拖动
    @Override
    public boolean isLongPressDragEnabled() {
        return isLongPressDragEnabled;
    }

    //是否支持滑动操作
    @Override
    public boolean isItemViewSwipeEnabled() {
        return isItemViewSwipeEnabled;
    }
}

（2）代码中实现

ItemTouchHelper itemTouchHelper = new ItemTouchHelper(new RecyclerItemTouchCallback(adapter));
itemTouchHelper.attachToRecyclerView(recyclerView);

四、自定义分割线

（1）自定义分割线

• 查看ItemDecoration源码

    public abstract static class ItemDecoration {

        //在item绘制之前调用绘制
        public void onDraw(@NonNull Canvas c, @NonNull RecyclerView parent, @NonNull State state) {
            onDraw(c, parent);
        }

        @Deprecated
        public void onDraw(@NonNull Canvas c, @NonNull RecyclerView parent) {
        }

        //在item绘制之后调用绘制
        public void onDrawOver(@NonNull Canvas c, @NonNull RecyclerView parent,
                @NonNull State state) {
            onDrawOver(c, parent);
        }

        @Deprecated
        public void onDrawOver(@NonNull Canvas c, @NonNull RecyclerView parent) {
        }

        @Deprecated
        public void getItemOffsets(@NonNull Rect outRect, int itemPosition,
                @NonNull RecyclerView parent) {
            outRect.set(0, 0, 0, 0);
        }

        //设置item偏移量
        public void getItemOffsets(@NonNull Rect outRect, @NonNull View view,
                @NonNull RecyclerView parent, @NonNull State state) {
            getItemOffsets(outRect, ((LayoutParams) view.getLayoutParams()).getViewLayoutPosition(),
                    parent);
        }
    }

• 实现ItemDecoration自定义分割线

public class CustomDecoration extends RecyclerView.ItemDecoration {
    //分割线缩进值
    private int inset;
    private Paint paint;
    private int mOrientation;
    private Drawable mDivider;
    public static final int VERTICAL_LIST = LinearLayoutManager.VERTICAL;
    public static final int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL;

    public CustomDecoration(Context context, int orientation, int inset) {
        this.inset = inset;
        paint = new Paint();
        paint.setAntiAlias(true);
        paint.setStyle(Paint.Style.FILL);
        paint.setColor(context.getResources().getColor(R.color.colorPrimary));
        setOrientation(orientation);
    }

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

    public void setDrawable(Drawable drawable) {
        if (drawable == null) {
            throw new IllegalArgumentException("Drawable cannot be null.");
        }
        mDivider = drawable;
    }

    @Override
    public void onDraw(@NonNull Canvas c, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
        if (parent.getLayoutManager() == null || mDivider == null) {
            return;
        }
        if (mOrientation == VERTICAL_LIST) {
            drawVertical(c, parent);
        } else {
            drawHorizontal(c, parent);
        }
    }

    private void drawVertical(Canvas canvas, RecyclerView parent) {
        final int left = parent.getPaddingLeft();
        final int right = parent.getWidth() - parent.getPaddingRight();
        final int childCount = parent.getChildCount();
        //最后一个item不画分割线
        for (int i = 0; i < childCount - 1; 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();
            if (inset > 0) {
                canvas.drawRect(left, top, right, bottom, paint);
                mDivider.setBounds(left + inset, top, right - inset, bottom);
            } else {
                mDivider.setBounds(left, top, right, bottom);
            }
            mDivider.draw(canvas);
        }
    }

    private void drawHorizontal(Canvas canvas, 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 - 1; 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(canvas);
        }
    }

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

• 在代码中使用

CustomDecoration d = new CustomDecoration(this, CustomDecoration.VERTICAL_LIST, 0);
d.setDrawable(R.drawable.decoration);
recyclerView.addItemDecoration(d);

五、增加下拉刷新、上拉加载更多

（1）SwipeRefreshLayout下拉刷新

• 在xml文件中RecyclerView外部嵌套一个SwipeRefreshLayout
• 在代码中实现SwipeRefreshLayout.OnRefreshListener接口

swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
    @Override
    public void onRefresh() {
        //开始刷新，设置刷新可见
        swipeRefreshLayout.setRefreshing(true);
        //向头部插入数据
        List<String> list = new ArrayList<String>();
        for (int i = 0; i < 5; i++) {
            int index = i + 1;
            list.add("new item" + index);
        }
        adapter.onItemAddList(list);
        //加载数据结束，设置刷新不可见
        swipeRefreshLayout.setRefreshing(false);
    }
});

• 在adapter中添加onItemAddList方法

public void onItemAddList(List<String> list){
    list.addAll(this.list);
    this.list.clear();
    this.list.addAll(list);
    notifyDataSetChanged();
}

（2）上拉加载更多数据

• RecyclerView实现OnScrollListener接口实现滑动监听

recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
    @Override
    public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
        super.onScrollStateChanged(recyclerView, newState);
        //停止滑动
        if (newState == RecyclerView.SCROLL_STATE_IDLE) {
            int lastItemPosition = layoutManager.findLastCompletelyVisibleItemPosition();
            int itemCount = layoutManager.getItemCount();
            //判断是否滑动到了最后一个item，并且是向上滑动
            if (lastItemPosition == (itemCount - 1) && isSlidingUpward) {
                List<String> list = new ArrayList<String>();
                for (int i = 0; i < 5; i++) {
                    int index = i + 1;
                    list.add("more item" + index);
                }
                adapter.onItemIncrease(list);
            }
        }
    }

    @Override
    public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
        super.onScrolled(recyclerView, dx, dy);
        //dy大于零表示正在向上滑动
        isSlidingUpward = dy > 0;
    }
});

• 在adapter中添加刷新数据方法

public void onItemIncrease(List<String> list){
    this.list.addAll(list);
    notifyDataSetChanged();
}