Android之RecyclerView輕松實現下拉刷新和加載更多示例

2019-12-12 03:42:11

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來源：轉載

供稿：網友

今天研究了下RecyclerView的滑動事件，特別是下拉刷新和加載更多事件，在現在幾乎所有的APP顯示數據列表時都用到了。自定義RecyclerView下拉刷新和加載更多聽上去很復雜，實際上并不難，只要是對滑動事件的監聽和處理。

一、自定義RecyclerView實現下拉刷新和加載更多

1、如何判斷RecyclerView是在上滑還是下滑

在RecyclerView的OnScrollListener滑動事件監聽中有個好用的方法，就是onScrolled(RecyclerView recyclerView, int dx, int dy)，其中根據dx的值的正負就可以判斷是在左滑還是右滑，而根據dy的值就可以判斷是在上滑還是下滑。

//上滑if(dy>0){//相應操作代碼}//下滑else if(dy<0){//相應操作代碼}

2、如何判斷是否滑到了頂部或者底部

同樣在RecyclerView的OnScrollListener滑動事件監聽中onScrolled(RecyclerView recyclerView, int dx, int dy)方法中處理，根據canScrollVertically(int direction)來進行判斷。

//是否滑到底部if(!recyclerView.canScrollVertically(1)){ //相應處理操作}//是否滑到頂部if(!recyclerView.canScrollVertically(-1)){ //相應處理操作}

3、自定義RecyclerView

知道了滑動事件的判斷和處理，就可以很輕松得實現下拉刷新和加載更多了。

import android.content.Context;import android.support.annotation.Nullable;import android.support.v7.widget.RecyclerView;import android.util.AttributeSet;import android.util.Log;/** * Package:com.liuting.library * author:liuting * Date:2017/2/14 * Desc:自定義RecycleView，下拉刷新以及上拉加載更多 */public class RefreshLoadMoreRecycleView extends RecyclerView { private Boolean isLoadMore;//是否可以加載更多標志 private Boolean isLoadEnd;//加載到最后的標志 private Boolean isLoadStart;//頂部的標志 private Boolean isRefresh;//是否可以下拉刷新標志 private int lastVisibleItem;//最后一項 private IOnScrollListener listener;//事件監聽 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 兩種效果自己看著來    if (newState == RecyclerView.SCROLL_STATE_IDLE) {     if (isLoadEnd) {      // 判斷是否已加載所有數據      if (isLoadMore) {//未加載完所有數據，加載數據，并且還原isLoadEnd值為false，重新定位列表底部       if (getListener() != null) {        getListener().onLoadMore();       }      } else {//加載完了所有的數據       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){     //是否滑到頂部     if(!recyclerView.canScrollVertically(-1)){      isLoadStart=true;     }else{      isLoadStart=false;     }    }   }  }); } //監聽事件 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; } //設置是否支持加載更多 public void setLoadMoreEnable(Boolean loadMore) {  isLoadMore = loadMore; } public Boolean getRefresh() {  return isRefresh; } //設置是否支持下拉刷新 public void setRefreshEnable(Boolean refresh) {  isRefresh = refresh; }}

二、實際用例

已經定義好了RecyclerView，下面在Demo中實際使用和處理。

1、定義布局

布局文件很簡單，就是一個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、定義RecyclerView.Adapter

RecyclerView.Adapter在這里就簡單處理了，列表布局直接使用Android自帶的。

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中定義好控件以及數據加載操作

實現自定義RecyclerView中的數據加載事件監聽，刷新、加載更多以及加載完成。

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;//加載更多 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); } /**  * 加載數據  */ 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、最終效果圖