Android获取服务器Json字符串并显示在ListView上面

已经好久没有更新博客，今天终于有新的东西可以记录了。

通过这次的任务学习到了以前没有注意到的知识点，真的有种书读百遍，其义自见的感觉。这次又重新认识了《Handler消息机制原理》。这次的任务中有更新UI。但是忘记了在Android4.0以后不能在UI线程访问网络，子线程也不能更新UI界面。下面我来展示一下这次的效果图。

这次的任务是：获取服务器端的json字符串，并解析显示在Android界面上。

当我接到这个任务的时候，首先想到的是利用Fragment布局加上ListView布局。但是因为没有完全掌握，所以失败了。这是就想到了现在的方案。利用GridView加上ListView来实现。布局是没有问题。但是写代码的时候却出现了问题。当我获取到数据并顺利解析的时候。却怎么也传不到ListView。总是显示它的size为0.但是通过打印确实获取到了。这个时候老师让我利用Handler，便能顺利解决问题了。原因就是一开始，我写到的不能在子线程更新UI。

下面我来粘出我的代码以供大家参考：

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="@drawable/set_bj">
 <GridView
        android:id="@+id/gv_icons"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:numColumns="4"
        android:layout_alignParentBottom="true">

    </GridView>
</RelativeLayout>

item_gridview.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="10dp">

<TextView
    android:id="@+id/tv_icons"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:hint="功能"
    android:layout_centerInParent="true"
    android:textSize="13sp"
    android:textColor="#000000"/>

</RelativeLayout>

activity_select.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" >
 <LinearLayout
     android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="5dp"
    android:orientation="horizontal">
         <TextView
      android:id="@+id/tv_id"
      android:layout_width="0dp"
      android:layout_weight="2"
      android:textColor="@android:color/black"
      android:layout_height="wrap_content"

      android:textSize="15sp"
      android:text="题号"/>
        <TextView
      android:id="@+id/tv_name"
       android:layout_width="0dp"
      android:layout_weight="1"

      android:layout_height="wrap_content"
      android:textSize="15sp"
      android:text="题目"/>
        <TextView
      android:id="@+id/tv_tech"
       android:layout_width="0dp"
      android:layout_weight="7"
      android:gravity="center"
      android:layout_height="wrap_content"
      android:textSize="15sp"
      android:text="要求"/> 

 </LinearLayout>

     <ListView
         android:id="@+id/lv"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:layout_marginLeft="5dp">
     </ListView>  

</LinearLayout>

item_listview.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="horizontal" >
              <TextView
      android:id="@+id/tv_id"
      android:layout_width="0dp"
      android:layout_weight="1"
      android:textColor="@android:color/black"
      android:layout_height="wrap_content"
      android:gravity="center"
      android:text="题号"/>
        <TextView
      android:id="@+id/tv_name"
       android:layout_width="0dp"
      android:layout_weight="3"
      android:gravity="center"
      android:layout_height="wrap_content"
      android:text="题目"/>
        <TextView
      android:id="@+id/tv_tech"
       android:layout_width="0dp"
      android:layout_weight="6"
      android:gravity="center"
      android:layout_height="wrap_content"
      android:text="要求"/> 

</LinearLayout>

MainActivity.java

package com.rjxy.student;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.TextView;

public class MainActivity extends Activity {
    private GridView gv_Home;
    private String[] settingText = {"全部题目","我的选题","个人信息","我的密码"};

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        gv_Home = (GridView) findViewById(R.id.gv_icons);
        gv_Home.setAdapter(new MyAdapter());
        gv_Home.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> adapter, View view, int position,
                    long id) {
                System.out.println(position);
                switch (position) {
                case 0:
                    //查看全部题目

                    Intent intent = new Intent(MainActivity.this,SetlectActivity.class);
                    startActivity(intent);
                    break;
                case 1:
                    //我的选题
                    break;
                case 2:
                    //个人信息
                    break;
                case 3:
                    //修改密码
                    break;
                default:

                    break;
                }

            }

        });
    }

class MyAdapter extends BaseAdapter{

    @Override
    public int getCount() {

        return settingText.length;
    }

    @Override
    public Object getItem(int position) {

        return settingText[position];
    }

    @Override
    public long getItemId(int position) {

        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view = View.inflate(getApplicationContext(), R.layout.item_gridview, null);
        TextView tv_Home = (TextView) view.findViewById(R.id.tv_icons);
        tv_Home.setText(settingText[position]);
        return view;
    }

}

}

SetlectActivity.java

package com.rjxy.student;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class SetlectActivity extends Activity {
    private static final int CHANGE_UI = 1;
    private static final int ERROR = 2;
    private ListView lv;
    private List<Data> datas = new ArrayList<Data>();
    //主线程创建消息处理器
    private Handler handler = new Handler(){
        public void handleMessage(android.os.Message msg) {
            if (msg.what == CHANGE_UI) {
                try {
                    JSONArray arr = new JSONArray((String)msg.obj);
                      for (int i = 0; i < arr.length(); i++) {
                          JSONObject temp = (JSONObject) arr.get(i);
                         // Log.d("json", temp.getInt("id")+temp.getString("exp_name")+temp.getString("exp_tech"));
                          Data data = new Data();
                          data.setId(temp.getInt("id"));
                          data.setExp_name(temp.getString("exp_name"));
                          data.setExp_tech(temp.getString("exp_tech"));
                         //这个地方可以获取到值但是适配器那位0
                          datas.add(data);

                      }
                      lv.setAdapter(new MyAdapter());
                } catch (JSONException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        };
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_select);
        lv = (ListView) findViewById(R.id.lv);
        select();

    }

    private void select(){
        //子线程更新UI
         new Thread(){
                public void run(){
                    StringBuilder builder = new StringBuilder();
                    HttpClient client = new DefaultHttpClient();
                    String path = "http://10.6.78.254:2016/xampp/graduate/index.php/home/Student/test_android";
                    HttpGet httpGet = new HttpGet(path);
                    try {
                    HttpResponse response = client.execute(httpGet);
                    StatusLine statusLine = response.getStatusLine();
                    int statusCode = statusLine.getStatusCode();
                    if (statusCode == 200) {

                      BufferedReader reader = new BufferedReader
                                  (new InputStreamReader(response.getEntity().getContent(),"UTF-8"));
                          for(String s=reader.readLine();s!=null;s=reader.readLine())
                          {
                              builder.append(s);
                          }
                          String content = builder.toString();
                        //通知主线程更新UI
                          Message message = new Message();
                          message.what = CHANGE_UI;
                          message.obj = content;
                          handler.sendMessage(message);
                    }else{
                        Log.e(MainActivity.class.toString(), "Failed");
                    }
                } catch (ClientProtocolException e) {

                    e.printStackTrace();
                } catch (IOException e) {

                    e.printStackTrace();
                }

                };
            }.start();
    }
     class MyAdapter extends BaseAdapter{

            @Override
            public int getCount() {
                Log.d("AAA", ""+datas.size());
                return datas.size();

            }

            @Override
            public Object getItem(int position) {

                return datas.get(position);
            }

            @Override
            public long getItemId(int position) {

                return position;
            }

            @Override
            public View getView(int position, View convertView, ViewGroup parent) {
                View view = View.inflate(SetlectActivity.this, R.layout.item_listview, null);
                TextView id = (TextView) view.findViewById(R.id.tv_id);
                TextView exp_name = (TextView) view.findViewById(R.id.tv_name);
                TextView exp_tech = (TextView) view.findViewById(R.id.tv_tech);
                Data data = datas.get(position);
                Log.d("aaaaa",datas.get(position).getExp_name() );

                id.setText(String.valueOf(datas.get(position).getId()));
                exp_name.setText(datas.get(position).getExp_name());
                //Log.i("exp_name", datas.get(position).getExp_name());
                exp_tech.setText(datas.get(position).getExp_tech());
                return view;
            }

     }
}

Data.java

package com.rjxy.student;

public class Data {
    private int id;
    private String exp_name;
    private String exp_tech;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getExp_name() {
        return exp_name;
    }
    public void setExp_name(String exp_name) {
        this.exp_name = exp_name;
    }
    public String getExp_tech() {
        return exp_tech;
    }
    public void setExp_tech(String exp_tech) {
        this.exp_tech = exp_tech;
    }
    @Override
    public String toString() {
        return "Data [id=" + id + ", exp_name=" + exp_name + ", exp_tech="
                + exp_tech + "]";
    }

}

添加权限：

<uses-permission android:name="android.permission.INTERNET"/>

服务器端的代码：ThinkPHP代码为：

public function test_android(){

        $myModel = new \Think\Model();
        $result=$myModel->query("select id,exp_name,exp_tech from g_experiment ;");

        echo json_encode($result);

    }