Android RecyclerView实现上拉加载、分页 功能--拿来就能用
对初学者来说这简直。。。，网上例子找了一大堆，最后终于有了结果，现做记录留个笔记，自己参考
activity_recycler_view.xml
rv_recyclerview_item.xml
rv_recyclerview_item_footer.xml
下面是这个RecyclerViewActivity.java代码package com.example.demo;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.DefaultItemAnimator;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import androidx.swiperefreshlayout.widget.SwipeRefreshLayout;
import android.content.Context;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ProgressBar;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
/**
* @author zpn
* @date 2020-09-24
*/
public class RecyclerViewActivity extends AppCompatActivity implements SwipeRefreshLayout.OnRefreshListener {
private RecyclerView rv_recyclerview;
private SwipeRefreshLayout sr_layout;
private LinearLayoutManager mLayoutManager;
private List list;
private MyAdapter adapter;
private int lastVisibleItem = 0;
private final int PAGE_COUNT = 10;
private Handler mHandler = new Handler(Looper.getMainLooper());
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_recycler_view);
sr_layout = findViewById(R.id.sr_layout);
rv_recyclerview = findViewById(R.id.rv_recyclerview);
initData();
initRefreshLayout();
initRecyclerView();
}
private void initData() {
list = new ArrayList<>();
for (int i = 1; i <= 40; i++) {
list.add("条目" + i);
}
}
private void initRefreshLayout() {
//sr_layout.setColorSchemeResources(android.R.color.holo_blue_light, android.R.color.holo_red_light,
// android.R.color.holo_orange_light, android.R.color.holo_green_light);
sr_layout.setOnRefreshListener(this);
}
private void initRecyclerView() {
adapter = new MyAdapter(getDatas(0, PAGE_COUNT), this, getDatas(0, PAGE_COUNT).size() > 0 ? true : false);
mLayoutManager = new LinearLayoutManager(this);
rv_recyclerview.setLayoutManager(mLayoutManager);
rv_recyclerview.setAdapter(adapter);
rv_recyclerview.setItemAnimator(new DefaultItemAnimator());
rv_recyclerview.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (newState == RecyclerView.SCROLL_STATE_IDLE) {
if (adapter.isFadeTips() == false && lastVisibleItem + 1 == adapter.getItemCount()) {
mHandler.postDelayed(new Runnable() {
@Override
public void run() {
updateRecyclerView(adapter.getRealLastPosition(), adapter.getRealLastPosition() + PAGE_COUNT);
}
}, 500);
}
if (adapter.isFadeTips() == true && lastVisibleItem + 2 == adapter.getItemCount()) {
mHandler.postDelayed(new Runnable() {
@Override
public void run() {
updateRecyclerView(adapter.getRealLastPosition(), adapter.getRealLastPosition() + PAGE_COUNT);
}
}, 500);
}
}
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
lastVisibleItem = mLayoutManager.findLastVisibleItemPosition();
}
});
}
private List getDatas(final int firstIndex, final int lastIndex) {
List resList = new ArrayList<>();
for (int i = firstIndex; i < lastIndex; i++) {
if (i < list.size()) {
resList.add(list.get(i));
}
}
return resList;
}
private void updateRecyclerView(int fromIndex, int toIndex) {
List newDatas = getDatas(fromIndex, toIndex);
if (newDatas.size() > 0) {
adapter.updateList(newDatas, true);
} else {
adapter.updateList(null, false);
}
}
@Override
public void onRefresh() {
sr_layout.setRefreshing(true);
adapter.resetDatas();
updateRecyclerView(0, PAGE_COUNT);
mHandler.postDelayed(new Runnable() {
@Override
public void run() {
sr_layout.setRefreshing(false);
}
}, 1000);
}
public class MyAdapter extends RecyclerView.Adapter {
private List datas; // 数据源
private Context context; // 上下文Context
private int normalType = 0; // 第一种ViewType，正常的item
private int footType = 1; // 第二种ViewType，底部的提示View
private boolean hasMore = true; // 变量，是否有更多数据
private boolean fadeTips = false; // 变量，是否隐藏了底部的提示
public MyAdapter(List datas, Context context, boolean hasMore) {
// 初始化变量
this.datas = datas;
this.context = context;
this.hasMore = hasMore;
}
// 获取条目数量，之所以要加1是因为增加了一条footView
@Override
public int getItemCount() {
return datas.size() + 1;
}
// 自定义方法，获取列表中数据源的最后一个位置，比getItemCount少1，因为不计上footView
public int getRealLastPosition() {
return datas.size();
}
// 根据条目位置返回ViewType，以供onCreateViewHolder方法内获取不同的Holder
@Override
public int getItemViewType(int position) {
if (position == getItemCount() - 1) {
return footType;
} else {
return normalType;
}
}
// 正常item的ViewHolder，用以缓存findView操作
class NormalHolder extends RecyclerView.ViewHolder {
private TextView textView;
public NormalHolder(View itemView) {
super(itemView);
textView = (TextView) itemView.findViewById(R.id.tv_recycler);
}
}
// // 底部footView的ViewHolder，用以缓存findView操作
class FootHolder extends RecyclerView.ViewHolder {
private TextView tips;
private ProgressBar pb_footer_progressBar;
public FootHolder(View itemView) {
super(itemView);
tips = (TextView) itemView.findViewById(R.id.tv_footer);
pb_footer_progressBar = (ProgressBar)itemView.findViewById(R.id.pb_footer_progressBar);
}
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
// 根据返回的ViewType，绑定不同的布局文件，这里只有两种
if (viewType == normalType) {
return new NormalHolder(LayoutInflater.from(context).inflate(R.layout.rv_recyclerview_item, parent,false));
} else {
return new FootHolder(LayoutInflater.from(context).inflate(R.layout.rv_recyclerview_item_footer, parent,false));
}
}
@Override
public void onBindViewHolder(final RecyclerView.ViewHolder holder, int position) {
// 如果是正常的imte，直接设置TextView的值
if (holder instanceof NormalHolder) {
((NormalHolder) holder).textView.setText(datas.get(position));
} else {
if(getItemCount() < PAGE_COUNT){
((FootHolder) holder).tips.setVisibility(View.GONE);
((FootHolder) holder).pb_footer_progressBar.setVisibility(View.GONE);
}else {
// 之所以要设置可见，是因为我在没有更多数据时会隐藏了这个footView
((FootHolder) holder).tips.setVisibility(View.VISIBLE);
((FootHolder) holder).pb_footer_progressBar.setVisibility(View.VISIBLE);
// 只有获取数据为空时，hasMore为false，所以当我们拉到底部时基本都会首先显示“正在加载更多...”
if (hasMore == true) {
// 不隐藏footView提示
fadeTips = false;
if (datas.size() > 0) {
// 如果查询数据发现增加之后，就显示正在加载更多
((FootHolder) holder).tips.setText("正在加载更多...");
}
} else {
if (datas.size() > 0) {
// 如果查询数据发现并没有增加时，就显示没有更多数据了
((FootHolder) holder).tips.setText("没有更多数据了");
// 然后通过延时加载模拟网络请求的时间，在500ms后执行
mHandler.postDelayed(new Runnable() {
@Override
public void run() {
// 隐藏提示条
((FootHolder) holder).tips.setVisibility(View.GONE);
((FootHolder) holder).pb_footer_progressBar.setVisibility(View.GONE);
// 将fadeTips设置true
fadeTips = true;
// hasMore设为true是为了让再次拉到底时，会先显示正在加载更多
hasMore = true;
}
}, 500);
}
}
}
}
}
// 暴露接口，改变fadeTips的方法
public boolean isFadeTips() {
return fadeTips;
}
// 暴露接口，下拉刷新时，通过暴露方法将数据源置为空
public void resetDatas() {
datas = new ArrayList<>();
}
// 暴露接口，更新数据源，并修改hasMore的值，如果有增加数据，hasMore为true，否则为false
public void updateList(List newDatas, boolean hasMore) {
// 在原有的数据之上增加新数据
if (newDatas != null) {
datas.addAll(newDatas);
}
this.hasMore = hasMore;
notifyDataSetChanged();
}
}
}