ListView 分頁載入網路資料
阿新 • • 發佈:2019-01-02
1.分頁載入思路
(1)判斷是否滑動到底部
(2)當滑動到底部,往資料來源中新增資料,然後呼叫adapter.notifyDataSetChanged()方法重新整理顯示的listView資料。
2. 下面是糗事百科載入的例項,載入效果如下(為了顯示效果我在工作執行緒中休眠了 3s)
圖1
圖2
當載入資料的時候顯示進度,和文字提示,載入完成後,提示會隱藏掉。
3.下面貼出程式碼
主佈局:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.day36_808.fenpage2_listview.MainActivity">
<ListView
android:id="@+id/listview_main"
android:layout_width="match_parent"
android:layout_height ="match_parent" />
<!--正在載入資料時顯示,其餘時候隱藏-->
<LinearLayout
android:id="@+id/progress_container"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:gravity="center"
android:orientation ="horizontal" >
<ProgressBar
android:id="@+id/pb"
style="?android:attr/progressBarStyleSmall"
android:layout_width="25sp"
android:layout_height="25sp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="正在載入...."
android:textSize="25sp"
android:layout_marginLeft="10dp"/>
</LinearLayout>
</RelativeLayout>
ListView 的item佈局(普通文字顯示)
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:id="@+id/text_content"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:maxLines="2"
android:padding="8dp"
android:textColor="#515151"
android:ellipsize="end"
android:textSize="18sp"/>
</LinearLayout>
Java 程式碼(因為程式碼不多我就乾脆就在一個類中完成了)
package com.day36_808.fenpage2_listview;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.SystemClock;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class MainActivity extends Activity {
private String url = "http://m2.qiushibaike.com/article/list/suggest?page=";
private ListView listView;
private View viewById;
private int currPage=1; //當前顯示頁面
private ArrayList<Map<String, String>> totalist;
private MyAdapter adapter;
private boolean isBottom; //判讀是否到達底部
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.listview_main);
viewById = findViewById(R.id.progress_container);
//載入第一頁的資料
totalist = new ArrayList<>();
adapter = new MyAdapter(totalist);
listView.setAdapter(adapter);
new MyAsyncTask().execute(url + currPage);
//listView 的滾動監聽,當到達底部時自動載入資料
listView.setOnScrollListener(new AbsListView.OnScrollListener() {
@Override
public void onScrollStateChanged(AbsListView absListView, int state) {
//如果滾動狀態停止,併到達底部,使進度條和載入提示顯示,並載入資料
if (state==SCROLL_STATE_IDLE&&isBottom){
viewById.setVisibility(View.VISIBLE);
currPage=currPage+1;
new MyAsyncTask().execute(url+currPage);
}
}
@Override
public void onScroll(AbsListView absListView, int i, int i1, int i2) {
//判讀是否滑動到了底部
isBottom=((i+i1)==i2);
}
});
}
//使用非同步任務下載,並重新整理資料
//連網下載json, 更新ui(繫結資料到Listview)
class MyAsyncTask extends AsyncTask<String, Void, byte[]> {
@Override
protected byte[] doInBackground(String... params) {
try {
HttpURLConnection con = (HttpURLConnection) new URL(params[0]).openConnection();
con.setRequestMethod("GET");
con.setConnectTimeout(5000);
con.connect();
if (con.getResponseCode() == 200) {
BufferedInputStream bis = new BufferedInputStream(con.getInputStream());
ByteArrayOutputStream bos = new ByteArrayOutputStream();
int i;
while((i = bis.read()) != -1) {
bos.write(i);
bos.flush();
}
bis.close();
Log.d("lewis", "doInBackground: " + bos.toString());
SystemClock.sleep(3 * 1000);
return bos.toByteArray();
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(byte[] result) {
super.onPostExecute(result);
if (result != null) {
try {
String json = new String(result, "UTF-8");
List<Map<String, String>> list = parseJSON(json);
totalist.addAll(list);
adapter.notifyDataSetChanged();
} catch (Exception e) {
e.printStackTrace();
}
} else {
Toast.makeText(MainActivity.this, "網路異常!", Toast.LENGTH_SHORT).show();
}
viewById.setVisibility(View.GONE);
}
}
// json解析方法
private List<Map<String, String>> parseJSON(String json) {
List<Map<String, String>> list = new ArrayList<Map<String,String>>();
try {
JSONObject jsonObject = new JSONObject(json);
JSONArray array_items = jsonObject.getJSONArray("items");
for (int i = 0; i < array_items.length(); i++) {
JSONObject object_item = array_items.getJSONObject(i);
Map<String, String> itemMap = new HashMap<String, String>();
itemMap.put("content", object_item.getString("content"));
list.add(itemMap);
}
} catch (JSONException e) {
e.printStackTrace();
}
return list;
}
// 定義介面卡
private class MyAdapter extends BaseAdapter {
private List<Map<String,String>> mapList;
public MyAdapter(List<Map<String, String>> mapList) {
this.mapList = mapList;
}
@Override
public int getCount() {
return mapList.size();
}
@Override
public Object getItem(int i) {
return mapList.get(i);
}
@Override
public long getItemId(int i) {
return i;
}
@Override
public View getView(int position, View convertView, ViewGroup viewGroup) {
ViewHolder holder=null;
if (convertView==null){
holder=new ViewHolder();
convertView= LayoutInflater.from(getApplicationContext())
.inflate(R.layout.item_listview,viewGroup,false);
holder.text_content= (TextView) convertView.findViewById(R.id.text_content);
convertView.setTag(holder);
}else {
holder= (ViewHolder) convertView.getTag();
}
holder.text_content.setText(mapList.get(position).get("content"));
return convertView;
}
class ViewHolder{
TextView text_content;
}
}
}