Android之RecyclerView轻松实现下拉刷新和加载更多

今天研究了下RecyclerView的滑动事件，特别是下拉刷新和加载更多事件，在现在几乎所有的APP显示数据列表时都用到了。自定义RecyclerView下拉刷新和加载更多听上去很复杂，实际上并不难，只要是对滑动事件的监听和处理。

一、自定义RecyclerView实现下拉刷新和加载更多

1、如何判断RecyclerView是在上滑还是下滑

在RecyclerView的OnScrollListener滑动事件监听中有个好用的方法，就是onScrolled(RecyclerView recyclerView, int dx, int dy)，其中根据dx的值的正负就可以判断是在左滑还是右滑，而根据dy的值就可以判断是在上滑还是下滑。

 //上滑
 if(dy>0){
 //相应操作代码
 }
 //下滑
 else if(dy<0){
 //相应操作代码
 }

2、如何判断是否滑到了顶部或者底部

同样在RecyclerView的OnScrollListener滑动事件监听中onScrolled(RecyclerView recyclerView, int dx, int dy)方法中处理，根据canScrollVertically(int direction)来进行判断。

 //是否滑到底部
 if(!recyclerView.canScrollVertically(1)){
     //相应处理操作
 }
 //是否滑到顶部
 if(!recyclerView.canScrollVertically(-1)){
     //相应处理操作
 }

3、自定义RecyclerView

知道了滑动事件的判断和处理，就可以很轻松得实现下拉刷新和加载更多了。

 import android.content.Context;
 import android.support.annotation.Nullable;
 import android.support.v7.widget.RecyclerView;
 import android.util.AttributeSet;
 import android.util.Log;
 import android.view.MotionEvent;
 import android.view.View;

 /**
  * Package:com.liuting.library
  * author:liuting
  * Date:2017/2/14
  * Desc:自定义RecycleView，下拉刷新以及上拉加载更多
  */

 public class RefreshLoadMoreRecycleView extends RecyclerView implements RecyclerView.OnTouchListener{
     private Boolean isLoadMore;//加载更多标志
     private Boolean isLoadEnd;//加载到最后的标志
     private Boolean isLoadStart;//顶部的标志
     private Boolean isRefresh;//下拉刷新标志
     private int lastVisibleItem;//最后一项
     private IOnScrollListener listener;//事件监听
     private float mLastY;//监听移动的位置

     public RefreshLoadMoreRecycleView(Context context) {
         super(context);
         init(context);
     }

     public RefreshLoadMoreRecycleView(Context context, @Nullable AttributeSet attrs) {
         super(context, attrs);
         init(context);
     }

     public RefreshLoadMoreRecycleView(Context context, @Nullable AttributeSet attrs, int defStyle) {
         super(context, attrs, defStyle);
         init(context);
     }

      /**
      * 初始化
      *
      * @param context
      */
     public void init(Context context) {
         isLoadEnd=false;
         isLoadStart =true;

         this.addOnScrollListener(new RecyclerView.OnScrollListener() {
             @Override
             public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                 super.onScrollStateChanged(recyclerView, newState);
                 //SCROLL_STATE_DRAGGING  和   SCROLL_STATE_IDLE 两种效果自己看着来
                 if (newState == RecyclerView.SCROLL_STATE_IDLE) {
                     loadData();
                 }
             }

             @Override
             public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                 super.onScrolled(recyclerView, dx, dy);
                 //上滑
                 if(dy>0){
                     //是否滑到底部
                     if(!recyclerView.canScrollVertically(1)){
                         isLoadEnd = true;
                     }else{
                         isLoadEnd = false;
                     }
                     Log.e("TAG","Running--->>isLoadEnd:"+isLoadEnd+dy);
                 }else if(dy<0){
                     //是否滑到顶部
                     if(!recyclerView.canScrollVertically(-1)){
                         isLoadStart=true;
                     }else{
                         isLoadStart=false;
                     }

                 }
             }
         });
         this.setOnTouchListener(this);
     }

      /**
      *
      * 加载数据
      *
      */
     private void loadData() {
         if (isLoadEnd) {
             // 判断是否已加载所有数据
             if (isLoadMore) {//未加载完所有数据，加载数据，并且还原isLoadEnd值为false，重新定位列表底部
                 if (getListener() != null) {
                     getListener().onLoadMore();
                 }
             } else {//加载完了所有的数据
                 if(getListener()!=null){
                     getListener().onLoaded();
                 }
             }
             isLoadEnd = false;
         } else if (isLoadStart) {
             if(isRefresh){
                 if (getListener() != null) {
                     getListener().onRefresh();
                 }
                 isLoadStart=false;
             }
         }
     }

     @Override
     public boolean onTouch(View view, MotionEvent motionEvent) {
         if (mLastY == -1) {
             mLastY = motionEvent.getRawY();
         }
         switch (motionEvent.getAction()){
             case MotionEvent.ACTION_MOVE:
                 final float deltaY = motionEvent.getRawY() - mLastY;
                 mLastY = motionEvent.getRawY();
                 //向上移动
                 if(deltaY<0){
                     //是否滑到底部
                     if(!this.canScrollVertically(1)){
                         isLoadEnd = true;
                     }else{
                         isLoadEnd = false;
                     }
                 }
                 //向下移动
                 else if(deltaY>0) {
                     //是否滑到顶部
                     if (!this.canScrollVertically(-1)) {
                         isLoadStart = true;
                     } else {
                         isLoadStart = false;
                     }
                 }
                 break;
             case MotionEvent.ACTION_DOWN:
                 mLastY = motionEvent.getRawY();
                 break;
             default://重置
                 mLastY = -1;
                 break;
         }

         return false;
     }

     //事件监听
     public interface IOnScrollListener {
         void onRefresh();

         void onLoadMore();

         void onLoaded();
     }

     public IOnScrollListener getListener() {
         return listener;
     }

     //设置事件监听
     public void setListener(IOnScrollListener listener) {
         this.listener = listener;
     }

     public Boolean getLoadMore() {
         return isLoadMore;
     }

     //设置是否支持加载更多
     public void setLoadMoreEnable(Boolean loadMore) {
         isLoadMore = loadMore;
     }

     public Boolean getRefresh() {
         return isRefresh;
     }

     //设置是否支持下拉刷新
     public void setRefreshEnable(Boolean refresh) {
         isRefresh = refresh;
     }
 }

二、实际用例

已经定义好了RecyclerView，下面在Demo中实际使用和处理。

1、定义布局

布局文件很简单，就是一个RecyclerView

 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:id="@+id/activity_main"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical"
     tools:context="com.liuting.refreshloadmorelistview.MainActivity">

     <com.liuting.library.RefreshLoadMoreRecycleView
         android:id="@+id/main_recycle_view_data"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:scrollbars="none"
          />
 </LinearLayout>

2、定义RecyclerView.Adapter

RecyclerView.Adapter在这里就简单处理了，列表布局直接使用Android自带的。

 import android.content.Context;
 import android.support.v7.widget.RecyclerView;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.TextView;

 import java.util.List;

 /**
  * Package:com.liuting.refreshloadmorelistview.adapter
  * author:liuting
  * Date:2017/2/16
  * Desc:列表Adapter
  */

 public class RefreshLoadMoreRecycleAdapter extends RecyclerView.Adapter<RefreshLoadMoreRecycleAdapter.ViewHolder> {
     private List<String> list;
     private Context context;

     public RefreshLoadMoreRecycleAdapter(Context context,List<String> list) {
         this.context =context;
         this.list = list;
     }

     @Override
     public RefreshLoadMoreRecycleAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
         View view = LayoutInflater.from(parent.getContext()).inflate(android.R.layout.simple_expandable_list_item_1, parent, false);
         RefreshLoadMoreRecycleAdapter.ViewHolder viewHolder = new RefreshLoadMoreRecycleAdapter.ViewHolder(view);
         return viewHolder;
     }

     @Override
     public void onBindViewHolder(ViewHolder holder, int position) {
         holder.text.setText(list.get(position));
         holder.itemView.setTag(position);
     }

     @Override
     public int getItemCount() {
         return list.size();
     }

     class ViewHolder extends RecyclerView.ViewHolder{
         private TextView text;

         public ViewHolder(View itemView) {
             super(itemView);
             text=(TextView)itemView.findViewById(android.R.id.text1);
         }
     }
 }

3、在Activity中定义好控件以及数据加载操作

实现自定义RecyclerView中的数据加载事件监听，刷新、加载更多以及加载完成。

 import android.app.ProgressDialog;
 import android.os.Bundle;
 import android.os.Handler;
 import android.os.Message;
 import android.support.v7.app.AppCompatActivity;
 import android.support.v7.widget.LinearLayoutManager;
 import android.widget.Toast;

 import com.liuting.library.RefreshLoadMoreRecycleView;
 import com.liuting.refreshloadmorelistview.adapter.RefreshLoadMoreRecycleAdapter;

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

 public class MainActivity extends AppCompatActivity implements RefreshLoadMoreRecycleView.IOnScrollListener{
     private RefreshLoadMoreRecycleView recycleView;//下拉刷新RecycleView
     private List<String> list;//列表
     private RefreshLoadMoreRecycleAdapter adapter;//Adapter
     private ProgressDialog dialog;//提示框
     private static final int REFRESH_Load=0;//下拉刷新
     private static final int MORE_Load=1;//加载更多
     private Handler handler =new Handler(){
         @Override
         public void handleMessage(Message msg) {
             super.handleMessage(msg);
             switch (msg.what){
                 case REFRESH_Load:
                     recycleView.setLoadMoreEnable(true);
                     dismissDialog();
                     if(list!=null){
                         list.clear();
                     }
                     loadData();
                     adapter.notifyDataSetChanged();
                     break;
                 case MORE_Load:
                     recycleView.setLoadMoreEnable(false);
                     dismissDialog();
                     loadData();
                     adapter.notifyDataSetChanged();
                     break;
             }
         }
     };

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         initView();
     }

     public void initView(){
         dialog = new ProgressDialog(MainActivity.this);

         list=new ArrayList<>();
         loadData();
         recycleView = (RefreshLoadMoreRecycleView)findViewById(R.id.main_recycle_view_data);

         final LinearLayoutManager linearLayoutManager = new LinearLayoutManager(MainActivity.this);
         recycleView.setLayoutManager(linearLayoutManager);
         adapter = new RefreshLoadMoreRecycleAdapter(MainActivity.this,list);
         recycleView.setAdapter(adapter);
         recycleView.setListener(this);
         recycleView.setRefreshEnable(true);
         recycleView.setLoadMoreEnable(true);
     }

     /**
      * 加载数据
      */
     public void loadData(){
         for(int i=0;i<10;i++ ){
             list.add("It is "+i);
         }
     }

     @Override
     public void onRefresh() {
         showDialog();
         new Thread(){
             @Override
             public void run() {
                 super.run();
                 try {
                     sleep(5000);
                     handler.sendEmptyMessage(REFRESH_Load);
                 } catch (InterruptedException e) {
                     e.printStackTrace();
                 }
             }
         }.start();
     }

     @Override
     public void onLoadMore() {
         showDialog();
         new Thread(){
             @Override
             public void run() {
                 super.run();
                 try {
                     sleep(5000);
                     handler.sendEmptyMessage(MORE_Load);
                 } catch (InterruptedException e) {
                     e.printStackTrace();
                 }
             }
         }.start();
     }

     @Override
     public void onLoaded() {
         Toast.makeText(MainActivity.this,"Loaded all",Toast.LENGTH_SHORT).show();
     }

     /**
      * dismiss dialog
      */
     private void dismissDialog(){
         if (dialog!=null&&dialog.isShowing()){
             dialog.dismiss();
         }
     }

     /**
      * show dialog
      */
     private void showDialog(){
         if (dialog!=null&&!dialog.isShowing()){
             dialog.show();
         }
     }
 }

三、最终效果图

到这里就轻松实现了RecyclerView的下拉刷新和加载更多了。

源代码放在了Github上：https://github.com/LT5505/RefreshLoadMoreRecycleView