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;

/**
 * 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 {
 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;

/**
 * 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。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。