一手遮天 Android - view（RecyclerView）: RecyclerView 上拉加载更多数据
一手遮天 Android - view（RecyclerView）: RecyclerView 上拉加载更多数据
示例如下:
/view/recyclerview/RecyclerViewDemo4.java
/**
* 演示 RecyclerView 的上拉加载更多数据
*
* adapter 参见 RecyclerViewDemo4Adapter.java
* scroll 监听器参见 RecyclerViewDemo4OnScrollListener.java
*/
package com.webabcd.androiddemo.view.recyclerview;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.SystemClock;
import com.webabcd.androiddemo.R;
import java.util.List;
public class RecyclerViewDemo4 extends AppCompatActivity {
private RecyclerView _recyclerView;
// 数据分页的页索引
private int _pageIndex = 0;
// 数据分页的页大小
private int _pageSize = 20;
// 是否正在加载数据
private boolean _isLoading = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_view_recyclerview_recyclerviewdemo4);
_recyclerView = findViewById(R.id.recyclerView1);
sample();
}
private void sample() {
_recyclerView.setLayoutManager(new LinearLayoutManager(RecyclerViewDemo4.this));
// 初始数据
_recyclerView.setAdapter(new RecyclerViewDemo4Adapter(MyData.generateDataList(_pageIndex, _pageSize)));
_recyclerView.addOnScrollListener(new RecyclerViewDemo4OnScrollListener() {
@Override
public void onBottom() {
if (!_isLoading) {
// 加载更多数据
_pageIndex++;
_isLoading = true;
new MyTask().execute(_pageIndex, _pageSize);
}
}
});
}
// 异步加载数据
private class MyTask extends AsyncTask<Integer, Void, List<MyData>> {
@Override
protected List<MyData> doInBackground(Integer... params) {
SystemClock.sleep(1000);
int pageIndex = params[0];
int pageSize = params[1];
// 请求到更多数据
return MyData.generateDataList(pageIndex * pageSize, pageSize);
}
@Override
protected void onPostExecute(List<MyData> result) {
RecyclerViewDemo4Adapter adapter = (RecyclerViewDemo4Adapter)_recyclerView.getAdapter();
if (_pageIndex > 3) {
// 没有更多数据了
adapter.setHasMoreItems(false);
} else {
// 追加数据
adapter.appendData(result);
}
adapter.notifyDataSetChanged();
_isLoading = false;
}
}
}
\view\recyclerview\RecyclerViewDemo4Adapter.java
/**
* 自定义 RecyclerView.Adapter
*/
package com.webabcd.androiddemo.view.recyclerview;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.TextView;
import androidx.recyclerview.widget.RecyclerView;
import com.webabcd.androiddemo.R;
import java.util.List;
public class RecyclerViewDemo4Adapter extends RecyclerView.Adapter<RecyclerView.ViewHolder>
{
private List<MyData> _myDataList;
// 是否还有更多数据可供加载
private boolean _hasMoreItems = true;
public RecyclerViewDemo4Adapter(List<MyData> myDataList) {
_myDataList = myDataList;
}
// 追加数据
public void appendData(List<MyData> myDataList) {
_myDataList.addAll(myDataList);
}
// 告诉我是否还有更多数据可供加载
public void setHasMoreItems(boolean hasMoreItems) {
this._hasMoreItems = hasMoreItems;
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
if (viewType == 0) {
// 用于显示数据的 item
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_view_recyclerview_myrecyclerviewadapter_1, parent, false);
return new ViewHolder(view);
} else {
// 用于显示“加载更多”的 item
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_view_recyclerview_recyclerviewdemo8_loadmore, parent, false);
return new LoadMoreViewHolder(view);
}
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder viewHolder, int position) {
if (viewHolder instanceof ViewHolder) { // 用于显示数据的 item
ViewHolder holder = (ViewHolder)viewHolder;
MyData myData = _myDataList.get(position);
holder.imgLogo.setImageResource(myData.getLogoId());
holder.txtName.setText(myData.getName());
holder.txtComment.setText(myData.getComment());
} else if (viewHolder instanceof LoadMoreViewHolder) { // 用于显示“加载更多”的 item
LoadMoreViewHolder holder = (LoadMoreViewHolder)viewHolder;
if (!_hasMoreItems) { // 没有更多数据时
holder.textView.setText("没有更多数据了");
holder.progressBar.setVisibility(View.GONE);
} else { // 请求更多数据时
holder.textView.setText("正在加载");
holder.progressBar.setVisibility(View.VISIBLE);
}
}
}
@Override
public int getItemCount() {
// + 1 是因为多了一个“加载更多”的 item
return _myDataList.size() + 1;
}
@Override
public int getItemViewType(int position) {
if (position < _myDataList.size()) {
return 0; // 用于显示数据的 item
} else {
return 1; // 用于显示“加载更多”的 item
}
}
// 用于显示数据的 item 的 ViewHolder
class ViewHolder extends RecyclerView.ViewHolder {
private View container;
private ImageView imgLogo;
private TextView txtName;
private TextView txtComment;
public ViewHolder (View view) {
super(view);
container = view;
imgLogo = view.findViewById(R.id.imgLogo);
txtName = view.findViewById(R.id.txtName);
txtComment = view.findViewById(R.id.txtComment);
}
}
// 用于显示“加载更多”的 item 的 ViewHolder
class LoadMoreViewHolder extends RecyclerView.ViewHolder {
private View container;
private ProgressBar progressBar;
private TextView textView;
public LoadMoreViewHolder(View view) {
super(view);
container = view;
progressBar = view.findViewById(R.id.progressBar);
textView = view.findViewById(R.id.textView);
}
}
}
\view\recyclerview\RecyclerViewDemo4OnScrollListener.java
/**
* 自定义 RecyclerView.OnScrollListener
*/
package com.webabcd.androiddemo.view.recyclerview;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
public abstract class RecyclerViewDemo4OnScrollListener extends RecyclerView.OnScrollListener {
// 最近一次滑动是否是上滑
private boolean isSlidingUpward = false;
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
LinearLayoutManager manager = (LinearLayoutManager) recyclerView.getLayoutManager();
// 当不滑动时
if (newState == RecyclerView.SCROLL_STATE_IDLE) {
// 获取最后一个完全显示的 item 的 position
int lastItemPosition = manager.findLastCompletelyVisibleItemPosition();
int itemCount = manager.getItemCount();
// 判断是否滑动到了最后一个 item 并且是上滑
if (lastItemPosition == (itemCount - 1) && isSlidingUpward) {
// 滚动到底了
onBottom();
}
}
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
// 大于 0 代表上滑
isSlidingUpward = dy > 0;
}
/**
* 滚动到底的回调
*/
public abstract void onBottom();
}
/layout/activity_view_recyclerview_recyclerviewdemo4.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recyclerView1"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
/layout/item_view_recyclerview_myrecyclerviewadapter_1.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<ImageView
android:id="@+id/imgLogo"
android:layout_width="64dp"
android:layout_height="64dp" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:layout_weight="1">
<TextView
android:id="@+id/txtName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#1D1D1D"
android:textSize="24sp" />
<TextView
android:id="@+id/txtComment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#B4B4B4"
android:textSize="14sp" />
</LinearLayout>
</LinearLayout>
/layout/item_view_recyclerview_recyclerviewdemo8_loadmore.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="64dp"
android:gravity="center"
android:orientation="horizontal">
<ProgressBar
android:id="@+id/progressBar"
android:layout_width="32dp"
android:layout_height="32dp"
android:layout_gravity="center"
android:layout_marginRight="10dp"
android:indeterminateDrawable="@drawable/rotate_progressbar_indeterminate"
android:indeterminateDuration="500"
android:visibility="visible" />
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:textColor="#999999" />
</LinearLayout>
