学习使用线程下载json数据，并使用ListView显示出来的总结

来源：互联网发布：ue4是什么软件编辑：程序博客网时间：2024/04/30 03:43

1.首先要得到一个URL对象，把要访问的网页（json数据）得到

2 然后使用json解析，得到里面需要的对象

3 得到的对象封装成一个javabean形式，

4 使用适配器（adapter）显示到listview中，我使用的是baseadapter，simpleadapter也可以，但是baseadapter会比较通用一些，使用baseadapter要注意一下需要添加的方法

5 最后使用AsyncTask/Handler，将需要耗时间下载的json数据得到，防止主线程阻塞，也要注意使用AsyncTask/Handler时的一下具体使用方法，具体看代码

6 几个类都是在一个界面，希望大家多多包涵，分开的话就更好了，真是做的时候是简单的试一下

package com.example.personjson;

import java.util.ArrayList;
import java.util.List;

import org.json.JSONArray;
import org.json.JSONObject;

import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

import com.example.domain.Person;
import com.example.service.HtmlService;

public class MainActivity extends Activity {
//private TextView textView;
private ListView listView;
List<Person> persons;
JSONPersonService JSservie;
HtmlAsyncTask ht;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

            listView = (ListView)this.findViewById(R.id.listView);
            ht = new HtmlAsyncTask();//这里你忘了new对象
            ht.execute();
   //InputStream inStream = this.getClass().getClassLoader().getResourceAsStream("person.txt");

       /**try {

     JSONPersonService JSservice = new JSONPersonService();

     persons = JSservice.getJsonPersons();
     //InputStream instream = JSservice.getJsonPersons(inputStream);
    } catch (Exception e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }*/

           /** List<HashMap<String, Object>> data = new ArrayList<HashMap<String, Object>>();
            for(Person person : persons){
            HashMap<String, Object> item = new HashMap<String, Object>();
            item.put("title", person.getTitle());
            item.put("summary", person.getSummary());
            data.add(item);
            SimpleAdapter adapter = new SimpleAdapter(this, data, R.layout.listviewitem,
              new String[]{"title", "summary"}, new int[]{R.id.title, R.id.summary});
            listView.setAdapter(adapter);


            }*/


        }


    public class DemoAdapter extends BaseAdapter {
    private LayoutInflater myInflater;

  public int getCount() {
   // TODO Auto-generated method stub
   return persons.size();
  }

  public Person getItem(int position) {
   // TODO Auto-generated method stub
   return persons.get(position);
  }

  public long getItemId(int position) {
   // TODO Auto-generated method stub
   return position;
  }

  public View getView(int position, View convertView, ViewGroup parent) {
   // TODO Auto-generated method stub
   //初始化item的xml文件
   myInflater = LayoutInflater.from(MainActivity.this);
   convertView = myInflater.inflate(R.layout.listviewitem, null);



   //初始化控件
   TextView textViewTitle = (TextView)convertView.findViewById(R.id.title);
   TextView textViewSumm = (TextView)convertView.findViewById(R.id.summary);


   //从list里面取出单个对象

   Person person = getItem(position);

   //把值设定到具体的控件上
   textViewTitle.setText(person.getTitle());
   textViewSumm.setText(person.getSummary());//person.getSummary()，这里有点不一样

   return convertView;

  }

}

    public class HtmlAsyncTask extends AsyncTask<String, Integer, String> {

    public static final String TAG = "HtmlAsyncTask";

    //public HtmlAsyncTask(TextView textView) {
      //this.textView = textView;
    //}

    @Override
    protected String doInBackground(String... params) {
      // TODO Auto-generated method stub
      String html = "";
      persons = new ArrayList<Person>();
      try {
        html = HtmlService.getHtml("http://www.baike.com/api.php?datatype=json&m=article&a=new&baike_id=24669&start=0&limit=10&share=new");

        JSservie = new JSONPersonService();
        persons = JSservie.getJsonPersons(html);
      } catch (Exception e) {
       Log.e(TAG, e.toString());
      }

      return null;
     }

    @Override
    protected void onPostExecute(String result) {//result参数就是你doInBackground这个方法return的值
      //textView.setText(result);//更新UI
      DemoAdapter demoAdapter = new DemoAdapter();
      listView.setAdapter(demoAdapter);
    }

    @Override
    protected void onPreExecute() {
      // TODO Auto-generated method stub
      super.onPreExecute();
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
      // TODO Auto-generated method stub
      super.onProgressUpdate(values);
    }

    }

    public class JSONPersonService {

    public List<Person> getJsonPersons(String html) throws Exception{
       persons = new ArrayList<Person>();






      JSONObject josnObject = new JSONObject(html);
      //value值后面是个大括号，所以也是一个JSONObject对象，通过这种方式获取这个对象
      JSONObject jsonValue = josnObject.getJSONObject("value");
      //articlelist值后面是个中括号，所以是个JSONArray，通过这种方式获取JSONArray
      JSONArray array = jsonValue.getJSONArray("articlelist");
      for (int i = 0; i < array.length(); i++) {
       //从JSONArray集合中挨个取出JSONObject对象
       JSONObject JsonPerson = array.getJSONObject(i);
       //title，summary对应的值为String类型的，所以用JsonPerson.getString("")这个方法
       Person person = new Person(JsonPerson.getString("title"),JsonPerson.getString("summary"));
       persons.add(person);
      }



//      JSONArray array = new JSONArray(json);
//
//      for(int i=0; i < array.length() ; i++){
//       //JSONObject Person = (JSONObject) new JSONTokener(json).nextValue();
//       JSONObject Person = array.getJSONObject(i);
//       Person person = new Person(Person.getString("title"),Person.getString("summary"));
//
//       persons.add(person);
//
//
//      }
      return persons;
    }

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

}

得到json的数据

package com.example.service;

import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class HtmlService {

/**
* 获取网页的源代码
* @param path 网页路径
* @return
* @throws Exception
*/
public static String getHtml(String path) throws Exception{
  URL url = new URL(path);
  HttpURLConnection conn = (HttpURLConnection)url.openConnection();
  conn.setConnectTimeout(5 * 1000);
  conn.setRequestMethod("GET");
  if(conn.getResponseCode()==200){
   InputStream inStream = conn.getInputStream();
   byte[] data = readInputStream(inStream);//html的二进制数据
   //return new String(data);这是直接返回的数据，跟下面两行是一样的意思
   String json = new String(data,"UTF-8");
   return json;
  }else{
   throw new Exception("请求失败");
  }
}

/**
* 从输入流读取数据
* @param inStream
* @return
* @throws Exception
*/
public static byte[] readInputStream(InputStream inStream) throws Exception{
  ByteArrayOutputStream outSteam = new ByteArrayOutputStream();
  byte[] buffer = new byte[1024];
  int len = 0;
  while( (len = inStream.read(buffer)) !=-1 ){
   outSteam.write(buffer, 0, len);
  }
  outSteam.close();
  inStream.close();
  return outSteam.toByteArray();
}

}

javabean：

package com.example.domain;

public class Person {
private String title;
private String summary;

public Person(){}

public Person(String title, String summary) {
this.title = title;
this.summary = summary;
}

public String getTitle() {
return title;
}

public void setTitle(String title) {
this.title = title;
}

public String getSummary() {
return summary;
}

public void setSummary(String summary) {
this.summary = summary;
}

@Override
public String toString() {
return "Person [title=" + title + ", summary=" + summary + "]";
}

}

下面是两个XML文件和manifest文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<LinearLayout
   android:orientation="horizontal"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content">
    />
   <TextView
    android:layout_width="150dip"
    android:layout_height="wrap_content"
    android:text="标签"
    />
   <TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="明细"
    />
</LinearLayout>
<ListView
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:id="@+id/listView"
     />
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<TextView
   android:layout_width="150dip"
   android:layout_height="wrap_content"
   android:text="xxxxx"
   android:id="@+id/title"
   />
<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="明细"
     android:id="@+id/summary"
    />

</LinearLayout>

<uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="15" />
     
<uses-permission android:name="android.permission.INTERNET"/>

</manifest>