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"?>

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
bfec
{
private List list;
private Context context;

public RefreshLoadMoreRecycleAdapter(Context context,List 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 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。

源代码在Github上：https://github.com/LT5505/RefreshLoadMoreRecycleView