一手遮天 Android - view（ListView）: ListView 滚动到底部加载更多数据
一手遮天 Android - view（ListView）: ListView 滚动到底部加载更多数据
示例如下:
/view/listview/ListViewDemo8.java
/**
* ListView 滚动到底部加载更多数据
*
* 自定义的用于支持滚动到底部加载更多数据的 ListView 的代码参见 ListViewDemo8LoadMoreListView.java
*/
package com.webabcd.androiddemo.view.listview;
import android.content.Context;
import android.os.AsyncTask;
import android.os.SystemClock;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import com.webabcd.androiddemo.R;
import java.util.ArrayList;
import java.util.List;
public class ListViewDemo8 extends AppCompatActivity {
private ListViewDemo8LoadMoreListView _listView1;
// 数据源
private List<MyData> _myDataList = new ArrayList<MyData>();
// BaseAdapter
private MyAdapter _myAdapter;
// 数据分页的页索引
private int _pageIndex = 0;
// 数据分页的页大小
private int _pageSize = 20;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_view_listview_listviewdemo8);
_listView1 = (ListViewDemo8LoadMoreListView) findViewById(R.id.listView1);
sample();
}
private void sample() {
// 异步加载数据
new MyTask().execute(_pageIndex, _pageSize);
_myAdapter = new MyAdapter(_myDataList, this);
_listView1.setAdapter(_myAdapter);
// 告知 ListView 有更多数据可供加载
_listView1.setHasMoreItems(true);
// 处理 ListView 的需要加载更多数据的事件
_listView1.setOnLoadMoreListener(new ListViewDemo8LoadMoreListView.OnLoadMoreListener() {
@Override
public void onLoadMore() {
_pageIndex++;
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];
List<MyData> result = new ArrayList<MyData>();
for (int i = pageIndex * pageSize; i < pageIndex * pageSize + pageSize; i++) {
result.add(new MyData(R.drawable.img_sample_son, "name " + i, "comment " + i));
}
return result;
}
@Override
protected void onPostExecute(List<MyData> result) {
if (_pageIndex > 3) {
// 告知 ListView 没有更多数据可供加载了
_listView1.setHasMoreItems(false);
}
// 添加数据
_myDataList.addAll(result);
// 刷新 ListView
_myAdapter.notifyDataSetChanged();
// 告知 ListView 当前数据加载已经完成
_listView1.loadComplete();
}
}
// 自定义实体类
class MyData {
private int _logoId;
private String _name;
private String _comment;
public MyData() {
}
public MyData(int logoId, String name, String comment) {
this._logoId = logoId;
this._name = name;
this._comment = comment;
}
public int getLogoId() {
return _logoId;
}
public String getName() {
return _name;
}
public String getComment() {
return _comment;
}
public void setLogoId(int logoId) {
this._logoId = logoId;
}
public void setName(String name) {
this._name = name;
}
public void setComment(String comment) {
this._comment = comment;
}
}
// 自定义 BaseAdapter
class MyAdapter extends BaseAdapter {
private List<MyData> _myDataList;
private Context _context;
public MyAdapter(List<MyData> myDataList, Context context) {
this._myDataList = myDataList;
this._context = context;
}
// 需要呈现的 item 的总数
@Override
public int getCount() {
return _myDataList.size();
}
// 返回指定索引位置的 item 的对象
@Override
public Object getItem(int position) {
return _myDataList.get(position);
}
// 返回指定索引位置的 item 的 id
@Override
public long getItemId(int position) {
return position;
}
// 每构造一个 item 就会调用一次 getView() 来获取这个 item 的 view
// 每次绘制 item 都会调用 getView()
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
if (convertView == null) {
convertView = LayoutInflater.from(_context).inflate(R.layout.item_view_listview_listviewdemo8, parent, false);
holder = new ViewHolder();
holder.imgLogo = (ImageView) convertView.findViewById(R.id.imgLogo);
holder.txtName = (TextView) convertView.findViewById(R.id.txtName);
holder.txtComment = (TextView) convertView.findViewById(R.id.txtComment);
convertView.setTag(holder); // 将 holder 保存到 convertView 中
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.imgLogo.setBackgroundResource(_myDataList.get(position).getLogoId());
holder.txtName.setText(_myDataList.get(position).getName());
holder.txtComment.setText(_myDataList.get(position).getComment());
return convertView;
}
class ViewHolder {
ImageView imgLogo;
TextView txtName;
TextView txtComment;
}
}
}
\view\listview\ListViewDemo8LoadMoreListView.java
/**
* 自定义一个 ListView 用于支持滚动到底部加载更多数据
*/
package com.webabcd.androiddemo.view.listview;
import android.content.Context;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.AbsListView;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;
import com.webabcd.androiddemo.R;
public class ListViewDemo8LoadMoreListView extends ListView implements AbsListView.OnScrollListener {
// 用于显示“正在加载框”的 view
private View _rootView;
// “正在加载框”的 loading
private ProgressBar _progressBar;
// “正在加载框”的文字提示
private TextView _textView;
// 是否还有更多数据可供加载
private boolean _hasMoreItems = true;
// 是否正在加载数据
private boolean _isLoading = false;
public ListViewDemo8LoadMoreListView(Context context, AttributeSet attrs) {
super(context, attrs);
_rootView = LayoutInflater.from(context).inflate(R.layout.item_view_listview_listviewdemo8_loadmore, null);
_progressBar = (ProgressBar) _rootView.findViewById(R.id.progressBar);
_textView = (TextView) _rootView.findViewById(R.id.textView);
// 将“正在加载框”添加到 ListView 的 footer 中
super.addFooterView(_rootView, null, false);
// 监听 ListView 的滚动事件
super.setOnScrollListener(this);
}
// 外部调用，用于告诉 ListView 是否还有更多数据可供加载
public void setHasMoreItems(boolean hasMoreItems) {
this._hasMoreItems = hasMoreItems;
if (!hasMoreItems) {
_textView.setText("没有更多数据了");
_progressBar.setVisibility(View.GONE);
} else {
_textView.setText("正在加载");
_progressBar.setVisibility(View.VISIBLE);
}
}
// 外部调用，用于告诉 ListView 当前数据是否已经加载完成
public void loadComplete() {
_isLoading = false;
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
if (scrollState == OnScrollListener.SCROLL_STATE_IDLE) {
if (view.getLastVisiblePosition() == view.getCount() - 1 && !_isLoading && mOnLoadMoreListener != null && _hasMoreItems) {
_isLoading = true;
// 触发需要加载更多数据的事件
performLoadMore();
}
}
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
}
// ListView 需要获取更多数据时的事件
private OnLoadMoreListener mOnLoadMoreListener;
public interface OnLoadMoreListener {
void onLoadMore();
}
public void setOnLoadMoreListener(OnLoadMoreListener listener) {
mOnLoadMoreListener = listener;
}
protected void performLoadMore() {
if (mOnLoadMoreListener != null)
mOnLoadMoreListener.onLoadMore();
}
}
/layout/activity_view_listview_listviewdemo8.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">
<!--
com.webabcd.androiddemo.view.listview.ListViewDemo8LoadMoreListView - 自定义的用于支持滚动到底部加载更多数据的 ListView
-->
<com.webabcd.androiddemo.view.listview.ListViewDemo8LoadMoreListView
android:id="@+id/listView1"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</LinearLayout>
/layout/item_view_listview_listviewdemo8.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:paddingLeft="10dp"
android:orientation="horizontal">
<ImageView
android:id="@+id/imgLogo"
android:layout_width="64dp"
android:layout_height="64dp" />
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">
<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_listview_listviewdemo8_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:text="正在加载"
android:textColor="#999999" />
</LinearLayout>
