如何才能创建一个连接JSON通话的Android

Question

我在线路97

我觉得是，德JSON调用歌厅此错误显示java.lang.NullPointerException一个线程，因为没有得到数据，

我如何创建一个线程，为了获得这个数据，然后做下一步。

iam真的很新，所以任何帮助很好apreciate。

package com.zoada; 

import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStreamReader; 

import org.apache.http.HttpResponse; 
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.view.LayoutInflater; 
import android.view.Menu; 
import android.view.Window; 
import android.view.WindowManager; 
import android.widget.TableLayout; 
import android.widget.TableRow; 
import android.widget.TextView; 



public class MainActivity extends Activity { 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 

     // esconde el titlebar de la aplicaci�n 
     // tiene que estar antes de colocar el mainLayout 
     requestWindowFeature(Window.FEATURE_NO_TITLE); 
     // esconde el statusbar de Android 
     getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, 
       WindowManager.LayoutParams.FLAG_FULLSCREEN); 
     setContentView(R.layout.activity_main); 

     JSONArray posiciones = null; 

     // *** Comienza la comunicaci�n con el servidor 

     BufferedReader in = null; 
     try { 
      HttpClient client = new DefaultHttpClient(); 
      HttpGet request = new HttpGet("http://zoada.com/blah.php"); 
      HttpResponse response = client.execute(request); 


      // leyendo "response" un string gigantesco 
      in = new BufferedReader(
        new InputStreamReader(
          response.getEntity().getContent())); 

      // imprimpiendo el tarugo de texto linea a linea 

      StringBuffer sb = new StringBuffer(""); 
      String line = ""; 
      String NL = System.getProperty("line.separator"); 
      while ((line = in.readLine()) != null) { 
       sb.append(line + NL); 
      } 
      in.close(); 

      String page = sb.toString(); 
      //System.out.println(page); 

      //aqui viene la parte JSON!!! 

      JSONObject jObject = new JSONObject(page); 
      posiciones = jObject.getJSONArray("positions"); 

      for (int i=0; i< posiciones.length(); i++) { 
       JSONObject jo = posiciones.getJSONObject(i); 
       //System.out.println(jo.getString("name")); 
      } 
     } catch (Exception e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } finally { 
      if (in != null) { 
       try { 
        in.close(); 
       } catch (IOException e) { 
        e.printStackTrace(); 
       } 
      } 
     } 

     // *** termina comunicaci�n con el servidor 


     TableLayout tl = (TableLayout)findViewById(R.id.containerTable); 
     LayoutInflater inflater = getLayoutInflater(); 

     for (int i = 0; i < posiciones.length(); i++) { 
      try { 
       JSONObject jo = posiciones.getJSONObject(i); 

       TableRow row = (TableRow)inflater.inflate(R.layout.tablerow, tl, false); 

       TextView pos = (TextView)row.findViewById(R.id.position); 
       String posTxt=jo.getString("position"); 
       pos.setText(posTxt); 

       TextView team = (TextView)row.findViewById(R.id.team); 
       String teamTxt=jo.getString("name"); 
       team.setText(teamTxt); 

       TextView points = (TextView)row.findViewById(R.id.points); 
       String pointsTxt=jo.getString("points"); 
       points.setText(pointsTxt); 

       TextView games = (TextView)row.findViewById(R.id.games); 
       String gamesTxt=jo.getString("played"); 
       games.setText(gamesTxt); 

       TextView victories = (TextView)row.findViewById(R.id.victories); 
       String victoriesTxt=jo.getString("won"); 
       victories.setText(victoriesTxt); 

       TextView draw = (TextView)row.findViewById(R.id.draw); 
       String drawsTxt=jo.getString("draw"); 
       draw.setText(drawsTxt); 

       TextView lost = (TextView)row.findViewById(R.id.loss); 
       String loseTxt=jo.getString("lost"); 
       lost.setText(loseTxt); 

       TextView goals = (TextView)row.findViewById(R.id.goals); 
       int goalsInt = Integer.parseInt(jo.getString("gol")); 
       int againstInt = Integer.parseInt(jo.getString("against")); 
       String goalsTxt=goalsInt+":"+againstInt; 
       goals.setText(goalsTxt); 

       TextView diff = (TextView)row.findViewById(R.id.difference); 
       int diffInt=goalsInt-againstInt; 
       String diffTxt=""+diffInt; 
       diff.setText(diffTxt); 
/**/ 
       tl.addView(row);    
      } catch (JSONException e) { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      } 
     } 

     // text = (EditText) findViewById(R.id.EditText01); 

    } 

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

Answer 1

你不应该在UI线程中执行网络操作！ 例如，你可以在你的课堂上创建AsyncTask。 它可能类似于此

private class ParseTask extends AsyncTask<Params, Progress, Result> { 
    @Override 
    protected Result doInBackground(Params params) { 
     // get url 
     Params url = params[0]; 
     // create HttpClient etc. 
     ... 
     // get response, and parse json 
     // return 
     return result; 
    } 

    @Override 
    protected void onPostExecute (Result result) { 
     // now when you have result from parsed json, 
     // update application UI or whatever you need 
     someEditText.setText(value_from_result); 
    } 
} 

之后，只需在onCreate方法调用

ParseTask task = new ParseTask(); 
task.execute(url); 

开始的AsyncTask。

另一方面，通过在IntentService中处理json或者在一般情况下处理json，并且解析后的json通过广播返回到Activity，可以获得相同的效果。