详解Android RecyclerView

其他 2020-02-24 16:44:16 阅读次数: 0

目录

  • 点击事件
  • 添加、删除数据
  • 更丰富的条目展示(多条目展示)
  • 添加header 、footer
  • 下拉刷新、上拉加载更多

进阶一：点击事件、长按事件(实现adapter和Activity之间的通信)

RecyclerView要实现点击事件和长按事件可以在适配器中定义接口事件回调

1、定义对象
private OnItemClickListener mOnItemClickListener;
2、写接口，并定义方法
/**
* 通过在adapter定义接口实现回调
*/
public interface OnItemClickListener {
   //点击事件
   void onItemClick(View view, int position);

   //长按点击事件
   void onItemLongClick(View view, int position);
}
3、
public void setOnItemClickListener(OnItemClickListener mOnItemClickListener) {
        this.mOnItemClickListener = mOnItemClickListener;
}
4、在adapter需要的地方调用事件
if (mOnItemClickListener != null) {
   mOnItemClickListener.onItemClick(((ContentViewHolder) holder).llLayout, position - 1);
}
if (mOnItemClickListener != null) {
   mOnItemClickListener.onItemLongClick(((ContentViewHolder) holder).llLayout, position - 1);
}
5、Activity调用Adapter中的事件
recyclerViewAdapter.setOnItemClickListener(new RecyclerViewAdapter.OnItemClickListener() {
            @Override
            public void onItemClick(View view, int position) {
                Toast.makeText(RecycleActivity.this, "点击了第" + position + "条", Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onItemLongClick(View view, int position) {
                Toast.makeText(RecycleActivity.this, "长按了第" + position + "条", Toast.LENGTH_SHORT).show();
            }
});

image

进阶二：添加数据、删除某条数据

这里需要了解到刷新界面的多种方式

        notifyDataSetChanged();//刷新整体布局
        notifyItemChanged(position);//刷新指定position,会重新调用onBindViewHolder来进行刷新，如果当前position在屏幕之外，则不会调用，当重新滚动到屏幕内，会重新调用
        notifyItemRangeChanged(position, 10);//刷新从position开始之后10条数据
        notifyItemInserted(position);//在第position处插入数据，这个插入时会有动画
        notifyItemMoved(position,5);//将当前position移动到position为5的地方，并且刷新
        notifyItemRangeInserted(3,10);//批量增加
        notifyItemRemoved(position);//删除第position条数据
        notifyItemRangeRemoved(position, 10);//批量删除


/**
     * 删除某条数据
     *
     * @param position
     */
    public void removeData(int position) {
        mList.remove(position);
        notifyItemRemoved(position);
        notifyItemRangeChanged(position, mList.size());

    }
        /**
         * 在指定position添加数据
         *
         * @param position
         */
        public void addData(int position, String msg) {
            if (mList == null) {
                mList = new ArrayList<>();
            }
            if (position < mList.size()) {
                //说明这里是第一条
                mList.add(position, msg);
            } else {
                mList.add(msg);
                position = mList.size() - 1;
            }
            notifyItemInserted(position);
            notifyItemRangeChanged(position, mList.size());
        }
问题一：长按事件、点击事件同时发生

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-F5gkIlym-1580817649921)(//upload-images.jianshu.io/upload_images/15649819-5d960683419a4173.gif?imageMogr2/auto-orient/strip|imageView2/2/w/360/format/webp)]

解决思路

在public boolean onLongClick(View v) {return true}
需要消费掉这个长按事件 返回true

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-OMX7x7VO-1580817649922)(//upload-images.jianshu.io/upload_images/15649819-c63ab1c56a29a8c6.gif?imageMogr2/auto-orient/strip|imageView2/2/w/360/format/webp)]

进阶三：添加header、footer

思路
1、首先要区分头布局、中间布局、尾布局三种不同的type，通过设置一个int值来判断不同的布局
2、通过getItemViewType来返回type
3、在onCreateViewHolder中根据不同的viewType显示不同的布局
4、在onBindViewHolder根据不同的holder加载不同的数据
注意

1、getItemCount这里需要返回的集合的数量+header数量+footer数量
2、当content布局中加载数据是通过position获取数据时需要将
position-1

1、添加三种不同的type来区分不同的布局
public static final int ITEM_TYPE_CONTENT = 0;
public static final int ITEM_TYPE_FOOTER = 1;
public static final int ITEM_TYPE_HEADER = 2;
2、添加头、尾布局数量
private int footerCount = 1;
private int headerCount = 1;
3、根据position获取Item的类型
@Override
    public int getItemViewType(int position) {
        if (isHeaderView(position)) {
            return ITEM_TYPE_HEADER;
        } else if (isFooterView(position)) {
            return ITEM_TYPE_FOOTER;
        } else {
            return ITEM_TYPE_CONTENT;
        }
    }
4、根据不同的viewType显示不同的布局
 @NonNull
        @Override
        public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int viewType) {
            /**
             * 主要负责把加载子项的布局
             * 将xml定义的布局实例化为view对象
             */
            if (viewType == ITEM_TYPE_FOOTER) {
                View view = LayoutInflater.from(mContext).inflate(R.layout.recycler_footer_item, viewGroup, false);
                return new FooterViewHolder(view);
            } else if (viewType == ITEM_TYPE_HEADER) {
                View view = LayoutInflater.from(mContext).inflate(R.layout.recycler_header_item, viewGroup, false);
                return new HeaderViewHolder(view);
            } else if (viewType == ITEM_TYPE_CONTENT) {
                View view = LayoutInflater.from(mContext).inflate(R.layout.recyclerview_item, viewGroup, false);
                return new ContentViewHolder(view);
            }
            return null;
        }
5、根据不同的ViewHolder加载不同的数据(注意content中通过position加载数据position需要-1)
 @Override
            public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
                //主要负责绑定数据
                if (holder instanceof HeaderViewHolder) {

                } else if (holder instanceof FooterViewHolder) {

                } else if (holder instanceof ContentViewHolder) {
                    ((ContentViewHolder) holder).tvItem.setText(mList.get(position - 1));
                    ((ContentViewHolder) holder).llLayout.setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            if (mOnItemClickListener != null) {
                                mOnItemClickListener.onItemClick(((ContentViewHolder) holder).llLayout, position - 1);
                            }
                        }
                    });
                    ((ContentViewHolder) holder).llLayout.setOnLongClickListener(new View.OnLongClickListener() {
                        @Override
                        public boolean onLongClick(View v) {
                            if (mOnItemClickListener != null) {
                                mOnItemClickListener.onItemLongClick(((ContentViewHolder) holder).llLayout, position - 1);
                            }
                            return true;
                        }
                    });
                }

            }
6、返回的集合数量(务必加上header、footer)
@Override
                public int getItemCount() {
                    //返回集合的数量
                    return mList.size() + headerCount + footerCount;
                }
7、判断当前 item 是否是 FooterView
/**
     * 判断当前 item 是否是 FooterView
     */
    public boolean isFooterView(int position) {
        return footerCount != 0 && position >= (footerCount + mList.size());
    }
8、判断当前 item 是否是 HeaderView
/**
     * 判断当前 item 是否是 HeaderView
     */
    public boolean isHeaderView(int position) {
        return headerCount != 0 && position < headerCount;
    }
需加
class HeaderViewHolder extends RecyclerView.ViewHolder {

                        public HeaderViewHolder(@NonNull View itemView) {
                            super(itemView);
                        }
                    }

                    class FooterViewHolder extends RecyclerView.ViewHolder {

                            public FooterViewHolder(@NonNull View itemView) {
                                super(itemView);
                            }
                        }

image

问题一

当我们为recyclerView设置表格布局时，设置footer、header，如果不做任何处理就会出现下方错误

image

解决思路

1、通过setSpanSizeLookup重新设置显示的列数
2、通过判断当前view是footer、header,若是footer、header则占取整列，否则占取自己列

 @Override
    public void onAttachedToRecyclerView(@NonNull RecyclerView recyclerView) {
        RecyclerView.LayoutManager manager = recyclerView.getLayoutManager();
        if (manager instanceof GridLayoutManager) {
            //通过强转将manager转换成GridLayoutManager类型
            final GridLayoutManager gridLayoutManager = (GridLayoutManager) manager;
            //通过setSpanSizeLookup重新设置显示的列数
            gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {

                @Override
                public int getSpanSize(int position) {
                    //通过判断当前view是否是footer、header
                    //若是footer、header则占取整列，否则占取自己列
                  return (isHeaderView(position) || isFooterView(position)) ? gridLayoutManager.getSpanCount() : 1;
                }
            });
        }
    }

image

进阶四：下拉刷新、上拉加载更多

下拉刷新：在RecyclerView布局外层添加SwipeRefreshLayout
上拉加载更多：通过RecyclerView的addOnScrollListener来判断房前滚动的状态是否是最后一个Item，来进行加载更多

1、布局
<android.support.v4.widget.SwipeRefreshLayout
            android:id="@+id/swipe_refresh_layout"
            android:layout_width="match_parent"
            android:layout_height="match_parent">
        <android.support.v7.widget.RecyclerView
                android:id="@+id/recycleview"
                android:layout_width="match_parent"
                android:layout_height="match_parent"/>
    </android.support.v4.widget.SwipeRefreshLayout>
2、通过swipeRefreshLayout.setOnRefreshListener来进行下拉刷新
swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {
                Handler handler = new Handler();
                handler.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        /**
                         *要执行的操作
                         */
                        recyclerViewAdapter.addData(0, "我是刷新出来的数据");
                        swipeRefreshLayout.setRefreshing(false);
                        Toast.makeText(RecycleActivity.this, "下拉刷新成功", Toast.LENGTH_SHORT).show();
                    }
                }, 1500);//3秒后执行Runnable中的run方法
            }
        });
3、通过调用addOnScrollListener来进行加载更多

onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState)//滚动状态变化时的回调
onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy)//滚动时回调

mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            /**
             *
             * @param recyclerView 当前滚动的recyclerView
             * @param newState 当前滚动的状态
             *
             *  public static final int SCROLL_STATE_IDLE = 0;静止没有滚动
             *  public static final int SCROLL_STATE_DRAGGING = 1;正在被外部拖拽，即用户滑动
             *  public static final int SCROLL_STATE_SETTLING = 2;//自动滚动
             *
             *
             */
            @Override
            public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
                //滚动状态变化时的回调
                super.onScrollStateChanged(recyclerView, newState);
                //先判断当前状态是否已停止
                //判断最后一条数据+1是否是集合的数据
                //判断是否滑动到最底部
                if (newState == RecyclerView.SCROLL_STATE_IDLE && (lastVisibleItem + 1 == recyclerViewAdapter.getItemCount())) {
                    //判断总数>0 说明可以加载更多
                    if (total > 0) {
                        //判断total > count 说明还可以加载数据
                        if (total > count) {
                            Toast.makeText(RecycleActivity.this, "上拉加载", Toast.LENGTH_SHORT).show();
                            count += 10;//每次加载10条
                            getData();//加载的数据
                            recyclerViewAdapter.notifyDataSetChanged();//刷新适配器
                        } else {
                            Toast.makeText(RecycleActivity.this, "没有数据加载了", Toast.LENGTH_SHORT).show();
                        }
                    } else {
                        Toast.makeText(RecycleActivity.this, "没有数据加载了", Toast.LENGTH_SHORT).show();
                    }
                }
            }

            /**
             *
             * @param recyclerView 当前滚动的recyclerView
             * @param dx 水平滚动距离
             *           dx > 0 时为手指向左滚动,列表滚动显示右面的内容
             *           dx < 0 时为手指向右滚动,列表滚动显示左面的内容
             * @param dy 垂直滚动距离
             *           dy > 0 时为手指向上滚动,列表滚动显示下面的内容
             *           dy < 0 时为手指向下滚动,列表滚动显示上面的内容
             */
            @Override
            public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                //滚动时回调
                //最后一个可见Item
                lastVisibleItem = mLinearLayoutManager.findLastVisibleItemPosition();
            }
        });

image

整体代码

为了更好的方便查，我把Activity和Adapter放在一起写，开发中大家一定要分开逻辑来操作

package com.example.androidhightproject.module;

import android.content.Context;
import android.graphics.Rect;
import android.os.Bundle;
import android.os.Handler;
import android.support.annotation.NonNull;
import android.support.v4.widget.SwipeRefreshLayout;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.*;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;
import com.example.androidhightproject.R;

import java.util.ArrayList;
import java.util.List;

/**
 * @author dongbo
 */
public class RecycleActivity extends AppCompatActivity {

    private List<String> mList = new ArrayList<>();
    private RecyclerView mRecyclerView;
    private SwipeRefreshLayout swipeRefreshLayout;
    private int lastVisibleItem;

    private int total = 30;
    private int count = 10;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_recycle);
        mRecyclerView = (RecyclerView) findViewById(R.id.recycleview);
        swipeRefreshLayout = (SwipeRefreshLayout) findViewById(R.id.swipe_refresh_layout);

        /**
         * 设置布局管理器
         * 默认垂直排布  LinearLayoutManager.VERTICAL垂直  LinearLayoutManager.HORIZONTAL水平
         * boolean reverseLayout 默认是false 是否反转
         *
         */
        LinearLayoutManager mLinearLayoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
        mRecyclerView.setLayoutManager(mLinearLayoutManager);
        //设置纵向默认排列
//        mRecyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
        //设置横向默认排列,这里需要注意改成横向列表，分割线需要改成横向
//        mRecyclerView.setLayoutManager(new LinearLayoutManager(this,LinearLayoutManager.HORIZONTAL,false));
        //设置表格布局，这里需要注意的是，有很多需求是根据返回的数据显示表格的数量，所以分割线需要自己重新定义
//        mRecyclerView.setLayoutManager(new GridLayoutManager(this, 3));
        //设置瀑布流显示
//        mRecyclerView.setLayoutManager(new StaggeredGridLayoutManager(2, StaggeredGridLayoutManager.VERTICAL));
        //默认的分割线
        mRecyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL));
        //设置自定义分割线
//        mRecyclerView.addItemDecoration(new SpaceItemDecoation(3));
        //设置删除时的动画
        mRecyclerView.setItemAnimator(new DefaultItemAnimator());
        RecyclerViewAdapter recyclerViewAdapter = new RecyclerViewAdapter(getData(), this);
        mRecyclerView.setAdapter(recyclerViewAdapter);
        swipeRefreshLayout.setColorSchemeResources(R.color.colorAccent);

        swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {
                Handler handler = new Handler();
                handler.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        /**
                         *要执行的操作
                         */
                        recyclerViewAdapter.addData(0, "我是刷新出来的数据");
                        swipeRefreshLayout.setRefreshing(false);
                        Toast.makeText(RecycleActivity.this, "下拉刷新成功", Toast.LENGTH_SHORT).show();
                    }
                }, 1500);//3秒后执行Runnable中的run方法
            }
        });

        mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            /**
             *
             * @param recyclerView 当前滚动的recyclerView
             * @param newState 当前滚动的状态
             *
             *  public static final int SCROLL_STATE_IDLE = 0;静止没有滚动
             *  public static final int SCROLL_STATE_DRAGGING = 1;正在被外部拖拽，即用户滑动
             *  public static final int SCROLL_STATE_SETTLING = 2;//自动滚动
             *
             *
             */
            @Override
            public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
                //滚动状态变化时的回调
                super.onScrollStateChanged(recyclerView, newState);
                //先判断当前状态是否已停止
                //判断最后一条数据+1是否是集合的数据
                //判断是否滑动到最底部
                Log.e("newState", newState + "");
                if (newState == RecyclerView.SCROLL_STATE_IDLE && (lastVisibleItem + 1 == recyclerViewAdapter.getItemCount())) {
                    //判断总数>0 说明可以加载更多
                    if (total > 0) {
                        //判断total > count 说明还可以加载数据
                        if (total > count) {
                            Toast.makeText(RecycleActivity.this, "上拉加载", Toast.LENGTH_SHORT).show();
                            count += 10;//每次加载10条
                            getData();//加载的数据
                            recyclerViewAdapter.notifyDataSetChanged();//刷新适配器
                        } else {
                            Toast.makeText(RecycleActivity.this, "没有数据加载了", Toast.LENGTH_SHORT).show();
                        }
                    } else {
                        Toast.makeText(RecycleActivity.this, "没有数据加载了", Toast.LENGTH_SHORT).show();
                    }
                }
            }

            /**
             *
             * @param recyclerView 当前滚动的recyclerView
             * @param dx 水平滚动距离
             *           dx > 0 时为手指向左滚动,列表滚动显示右面的内容
             *           dx < 0 时为手指向右滚动,列表滚动显示左面的内容
             * @param dy 垂直滚动距离
             *           dy > 0 时为手指向上滚动,列表滚动显示下面的内容
             *           dy < 0 时为手指向下滚动,列表滚动显示上面的内容
             */
            @Override
            public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                //滚动时回调
                //最后一个可见Item
                Log.e("dx", dx + "");
                lastVisibleItem = mLinearLayoutManager.findLastVisibleItemPosition();
            }
        });
        recyclerViewAdapter.setOnItemClickListener(new RecyclerViewAdapter.OnItemClickListener() {
            @Override
            public void onItemClick(View view, int position) {
                Toast.makeText(RecycleActivity.this, "点击了第" + position + "条", Toast.LENGTH_SHORT).show();
                recyclerViewAdapter.addData(position, "我是添加的数据");
            }

            @Override
            public void onItemLongClick(View view, int position) {
                Toast.makeText(RecycleActivity.this, "长按了第" + position + "条", Toast.LENGTH_SHORT).show();
                recyclerViewAdapter.removeData(position);
            }
        });

    }

    private List<String> getData() {
        for (int i = 0; i < 10; i++) {
            mList.add("测试数据" + i);
//            mList.add("照片地址");
        }
        return mList;
    }
}

class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    /**
     * 首先要区分头布局、中间布局、尾布局三种不同的type，通过设置一个int值来判断不同的布局
     * 通过getItemViewType来返回type
     * 在onCreateViewHolder中根据不同的viewType显示不同的布局
     * 在onBindViewHolder根据不同的holder加载不同的数据
     * 注意：
     * 1、getItemCount这里需要返回的集合的数量+header数量+footer数量
     * 2、当content布局中加载数据是通过position获取数据时需要将position-1
     */
    private List<String> mList;
    private Context mContext;
    private OnItemClickListener mOnItemClickListener;

    public static final int ITEM_TYPE_CONTENT = 0;
    public static final int ITEM_TYPE_FOOTER = 1;
    public static final int ITEM_TYPE_HEADER = 2;

    private int footerCount = 1;
    private int headerCount = 1;

    public RecyclerViewAdapter(List<String> mList, Context mContext) {
        //大部分只有数据与上下文
        this.mList = mList;
        this.mContext = mContext;
    }

    public void setOnItemClickListener(OnItemClickListener mOnItemClickListener) {
        this.mOnItemClickListener = mOnItemClickListener;
    }

    /**
     * 删除某条数据
     *
     * @param position
     */
    public void removeData(int position) {
        notifyItemRemoved(position);
        mList.remove(position);
        notifyItemRangeChanged(position, mList.size());
    }

    /**
     * 在指定position添加数据
     *
     * @param position
     */
    public void addData(int position, String msg) {
        notifyItemInserted(position);
        if (mList == null) {
            mList = new ArrayList<>();
        }
        if (position < mList.size()) {
            //说明这里是第一条
            mList.add(position, msg);
        } else {
            mList.add(msg);
            position = mList.size() - 1;
        }
        notifyItemRangeChanged(position, mList.size());
    }

    @Override
    public int getItemViewType(int position) {
        if (isHeaderView(position)) {
            return ITEM_TYPE_HEADER;
        } else if (isFooterView(position)) {
            return ITEM_TYPE_FOOTER;
        } else {
            return ITEM_TYPE_CONTENT;
        }
    }

    @Override
    public void onAttachedToRecyclerView(@NonNull RecyclerView recyclerView) {
        RecyclerView.LayoutManager manager = recyclerView.getLayoutManager();
        if (manager instanceof GridLayoutManager) {
            //通过强转将manager转换成GridLayoutManager类型
            final GridLayoutManager gridLayoutManager = (GridLayoutManager) manager;
            //通过setSpanSizeLookup重新设置显示的列数
            gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {

                @Override
                public int getSpanSize(int position) {
                    //通过判断当前view是否是footer、header
                    //若是footer、header则占取整列，否则占取自己列
                    return (isHeaderView(position) || isFooterView(position)) ? gridLayoutManager.getSpanCount() : 1;
                }
            });
        }
    }

    @NonNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int viewType) {
        /**
         * 主要负责把加载子项的布局
         * 将xml定义的布局实例化为view对象
         */
        if (viewType == ITEM_TYPE_FOOTER) {
            View view = LayoutInflater.from(mContext).inflate(R.layout.recycler_footer_item, viewGroup, false);
            return new FooterViewHolder(view);
        } else if (viewType == ITEM_TYPE_HEADER) {
            View view = LayoutInflater.from(mContext).inflate(R.layout.recycler_header_item, viewGroup, false);
            return new HeaderViewHolder(view);
        } else if (viewType == ITEM_TYPE_CONTENT) {
            View view = LayoutInflater.from(mContext).inflate(R.layout.recyclerview_item, viewGroup, false);
            return new ContentViewHolder(view);
        }
        return null;
    }

    @Override
    public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
        //主要负责绑定数据
        if (holder instanceof HeaderViewHolder) {

        } else if (holder instanceof FooterViewHolder) {

        } else if (holder instanceof ContentViewHolder) {
//            Glide.with(mContext).load(mList.get(position-1)).into(((ContentViewHolder) holder).ivImage);
            ((ContentViewHolder) holder).tvItem.setText(mList.get(position - 1));
            ((ContentViewHolder) holder).llLayout.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if (mOnItemClickListener != null) {
                        mOnItemClickListener.onItemClick(((ContentViewHolder) holder).llLayout, position - 1);
                    }
                }
            });
            ((ContentViewHolder) holder).llLayout.setOnLongClickListener(new View.OnLongClickListener() {
                @Override
                public boolean onLongClick(View v) {
                    if (mOnItemClickListener != null) {
                        mOnItemClickListener.onItemLongClick(((ContentViewHolder) holder).llLayout, position - 1);
                    }
                    return true;
                }
            });
        }

    }

    @Override
    public int getItemCount() {
        //返回集合的数量
        return mList.size() + headerCount + footerCount;
    }

    class HeaderViewHolder extends RecyclerView.ViewHolder {

        public HeaderViewHolder(@NonNull View itemView) {
            super(itemView);
        }
    }

    class FooterViewHolder extends RecyclerView.ViewHolder {

        public FooterViewHolder(@NonNull View itemView) {
            super(itemView);
        }
    }

    class ContentViewHolder extends RecyclerView.ViewHolder {
//        private final ImageView ivImage;

        private final TextView tvItem;
        private final LinearLayout llLayout;

        public ContentViewHolder(@NonNull View itemView) {
            super(itemView);
            tvItem = (TextView) itemView.findViewById(R.id.tv_item);
            llLayout = (LinearLayout) itemView.findViewById(R.id.ll_layout);
//            ivImage = (ImageView) itemView.findViewById(R.id.iv_image);
        }
    }

    /**
     * 通过在adapter定义接口实现回调
     */
    public interface OnItemClickListener {
        //点击事件
        void onItemClick(View view, int position);

        //长按点击事件
        void onItemLongClick(View view, int position);
    }

    /**
     * 判断当前 item 是否是 FooterView
     */
    public boolean isFooterView(int position) {
        return footerCount != 0 && position >= (footerCount + mList.size());
    }

    /**
     * 判断当前 item 是否是 HeaderView
     */
    public boolean isHeaderView(int position) {
        return headerCount != 0 && position < headerCount;
    }
}

class SpaceItemDecoation extends RecyclerView.ItemDecoration {
    private int space;

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

    @Override
    public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        //如果不是第一个盒子设置一个居左和居下的边距
        outRect.left = space;
        outRect.bottom = space;
        //大部分的需求都是3个 因为第一个都是你设置个数的倍数，所以通过取余来将左边距设置为0
        if (parent.getChildLayoutPosition(view) % 3 == 0) {
            outRect.left = 0;
        }
    }
}

作者：江湖小白_董
链接：https://www.jianshu.com/p/6fc3251c8157

Android Developer
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