Question

我是android编程的新手，我有一个问题。我从thislink Json数据获取并将这些数据加载到我的自定义列表视图中，但是在加载时我崩溃了。错误是这样的：解析结果错误，http连接错误。

这是我的main.java，

package com.example.dovizkuru;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashMap;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
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.util.Log;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.Toast;



public class AnaEkran  extends Activity{
     public static final String URL = "http://api.piyasa.com/json/?kaynak=doviz_guncel_serb";  

     ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();

     @Override
    protected void onCreate(Bundle skr) {
        // TODO Auto-generated method stub
        super.onCreate(skr);
        setContentView(R.layout.anaekran);

        JSONObject json =getJSONfromURL(URL);       

       UyarıGoster("String mesaj");
        //Loop the Array
        try{    
        JSONArray  kurlar = json.getJSONArray("");
        for(int i=0;i < kurlar.length();i++){                       

            HashMap<String, String> map = new HashMap<String, String>();
            JSONObject e = kurlar.getJSONObject(i);

            map.put("foexid",  String.valueOf(i));
            map.put("foex", "Ad : " + e.getString("foex"));
            map.put("buy", "Alış : " + e.getString("buy"));
            map.put("sell", "Satış : " +  e.getString("sell"));
            mylist.add(map);
    }
        }
       catch(JSONException e)        {
         Log.e("log_tag", "Error parsing data "+e.toString());
       }


         SimpleAdapter adapter = new SimpleAdapter(getBaseContext(),
             mylist, R.layout.mymain,new String[] { "foex", "buy","sell" },
             new int[] {R.id.foex,R.id.tvParaAlis,R.id.tvParaSatis });

             ListView listView = ( ListView ) findViewById(R.id.listview);

            // Setting the adapter to the listView
            listView.setAdapter(adapter);

}



        private   void  UyarıGoster(String mesaj){
            Toast.makeText(getApplicationContext(),
                    mesaj, Toast.LENGTH_LONG)
                        .show();


            }


     public static String convertStreamToString(InputStream is){
            //burada gelen veriyi string değerine çevireceğiz
             BufferedReader reader = new BufferedReader(new InputStreamReader(is)); 
                StringBuilder sb = new StringBuilder(); 
                String line = null; 
                try { 
                  while ((line = reader.readLine()) != null) { 
                      sb.append(line).append("\n"); 
                  } 
                } catch (IOException e) { 
                } finally { 
                  try { 
                      is.close(); 
                  } catch (IOException e) { 
                  } 
                } 
                return sb.toString(); 
            }









     public static JSONObject getJSONfromURL(String url){

            //initialize
            InputStream is = null;
            String result = "";
            JSONObject jArray = null;

            //http post
            try{
                HttpClient httpclient = new DefaultHttpClient();
                HttpPost httppost = new HttpPost(url);
                HttpResponse response = httpclient.execute(httppost);
                HttpEntity entity = response.getEntity();
                is = entity.getContent();

            }catch(Exception e){
                Log.e("log_tag", "Error in http connection "+e.toString());
            }

            //convert response to string
            try{
                BufferedReader reader = new BufferedReader(new InputStreamReader(is));
                StringBuilder sb = new StringBuilder();
                String line = null;
                while ((line = reader.readLine()) != null) {
                    sb.append(line + "\n");
                }
                is.close();
                result=sb.toString();
            }catch(Exception e){
                Log.e("log_tag", "Error converting result "+e.toString());
            }

            //try parse the string to a JSON object
            try{
                    jArray = new JSONObject(result);
            }catch(JSONException e){
                Log.e("log_tag", "Error parsing data "+e.toString());
            }

            return jArray;
        } 


}

错误数据在这里

02-16 16:52:49.141: E/Trace(13341): error opening trace file: No such file or directory (2)
02-16 16:52:55.011: E/log_tag(13341): Error in http connection android.os.NetworkOnMainThreadException
02-16 16:52:55.011: E/log_tag(13341): Error converting result java.lang.NullPointerException
02-16 16:52:55.031: E/log_tag(13341): Error parsing data org.json.JSONException: End of input at character 0 of 
02-16 16:52:55.401: W/dalvikvm(13341): threadid=1: thread exiting with uncaught exception (group=0x40f91438)

Answer 1

您的第一个错误 android.os.NetworkOnMainThreadException 即将发布，因为您在主线程中解析了Json。尝试使用Asnync Class。如果您不想使用Async类而不是在onCreate中粘贴此代码。

if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
 }

Answer 2

首先使用BackGround中的AsyncTask调用Json From URL检查this链接，你正在做的是从主线程调用这是错误的，这就是为什么你得到 NETWORK ON MAIN THREAD EXCEPTION 我想这是导致应用崩溃的主要原因。

加载json数据并将其绑定到自定义布局

2 个答案: