Android之RecyclerView轻松实现下拉刷新和加载更多示例

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;

public class RefreshLoadMoreRecycleView extends RecyclerView {
 private Boolean isLoadMore;//是否可以加载更多标志
 private Boolean isLoadEnd;//加载到最后的标志
 private Boolean isLoadStart;//顶部的标志
 private Boolean isRefresh;//是否可以下拉刷新标志
 private int lastVisibleItem;//最后一项
 private IOnScrollListener listener;//事件监听
 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);
 }
 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) {
     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 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;
     }
    }
    //下滑
    else if(dy<0){
     //是否滑到顶部
     if(!recyclerView.canScrollVertically(-1)){
      isLoadStart=true;
     }else{
      isLoadStart=false;
     }
    }
   }
  });
 }
 //监听事件
 public interface IOnScrollListener {
  void onRefresh();
  void onLoadMore();
  void onLoaded();
 }
 public IOnScrollListener getListener() {
  return listener;
 }
 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;

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

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