JSON構文解析エラー文字列は

Question

私はこのコードを書いたと私はHTTPHandlerのなどを書いたが、私が実行したときにアプリの私は、エラーを見た：

............. 

のJava解析エラー：型のJavaの価値を。 lang.StringはJSONObjectに変換できません
インターネットで検索されましたが、解決できません。なにが問題ですか？どこにコードを追加すべきですか？

MainActivity.java

import android.os.AsyncTask; 
import android.os.Bundle; 
import android.support.v7.app.AppCompatActivity; 
import android.util.Log; 
import android.widget.ListAdapter; 
import android.widget.ListView; 
import android.widget.SimpleAdapter; 
import android.widget.Toast;  
import org.json.JSONArray; 
import org.json.JSONException; 
import org.json.JSONObject; 

import java.util.ArrayList; 
import java.util.HashMap; 

public class MainActivity extends AppCompatActivity { 

    private String TAG = MainActivity.class.getSimpleName(); 
    private ListView lv; 

    ArrayList<HashMap<String, String>> contactList; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     contactList = new ArrayList<>(); 
     lv = findViewById(R.id.list); 

     new GetContacts().execute(); 
    } 

    private class GetContacts extends AsyncTask<Void, Void, Void> { 
     @Override 
     protected void onPreExecute() { 
      super.onPreExecute(); 
      Toast.makeText(MainActivity.this, "Json Data is downloading", Toast.LENGTH_LONG).show(); 

     } 

     @Override 
     protected Void doInBackground(Void... arg0) { 
      HttpHandler sh = new HttpHandler(); 
      // Making a request to url and getting response 
      String url = "http://api.androidhive.info/contacts/"; 
      String jsonStr = sh.makeServiceCall(url); 

      Log.e(TAG, "Response from url: " + jsonStr); 
      if (jsonStr != null) { 
       try { 
        JSONObject jsonObj = new JSONObject(jsonStr); 

        // Getting JSON Array node 
        JSONArray contacts = jsonObj.getJSONArray("contacts"); 

        // looping through All Contacts 
        for (int i = 0; i < contacts.length(); i++) { 
         JSONObject c = contacts.getJSONObject(i); 
         String id = c.getString("id"); 
         String name = c.getString("name"); 
         String email = c.getString("email"); 

         // Phone node is JSON Object 
         JSONObject phone = c.getJSONObject("phone"); 
         String mobile = phone.getString("mobile"); 


         // tmp hash map for single contact 
         HashMap<String, String> contact = new HashMap<>(); 

         // adding each child node to HashMap key => value 
         contact.put("id", id); 
         contact.put("name", name); 
         contact.put("email", email); 
         contact.put("mobile", mobile); 

         // adding contact to contact list 
         contactList.add(contact); 
        } 
       } catch (final JSONException e) { 
        Log.e(TAG, "Json parsing error: " + e.getMessage()); 
        runOnUiThread(new Runnable() { 
         @Override 
         public void run() { 
          Toast.makeText(getApplicationContext(), 
            "Json parsing error: " + e.getMessage(), 
            Toast.LENGTH_LONG).show(); 
         } 
        }); 

       } 

      } else { 
       Log.e(TAG, "Couldn't get json from server."); 
       runOnUiThread(new Runnable() { 
        @Override 
        public void run() { 
         Toast.makeText(getApplicationContext(), 
           "Couldn't get json from server. Check LogCat for possible errors!", 
           Toast.LENGTH_LONG).show(); 
        } 
       }); 
      } 

      return null; 
     } 

     @Override 
     protected void onPostExecute(Void result) { 
      super.onPostExecute(result); 
      ListAdapter adapter = new SimpleAdapter(MainActivity.this, contactList, 
        R.layout.list_item, new String[]{"email", "mobile"}, 
        new int[]{R.id.email, R.id.mobile}); 
      lv.setAdapter(adapter); 
     } 
    } 
} 

HttpHandler.java

import android.util.Log; 

import java.io.BufferedInputStream; 
import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStream; 
import java.io.InputStreamReader; 
import java.net.HttpURLConnection; 
import java.net.MalformedURLException; 
import java.net.ProtocolException; 
import java.net.URL; 

public class HttpHandler { 

    private static final String TAG = HttpHandler.class.getSimpleName(); 

    public HttpHandler() { 
    } 

    public String makeServiceCall(String reqUrl) { 
     String response = null; 
     try { 
      URL url = new URL(reqUrl); 
      HttpURLConnection conn = (HttpURLConnection) url.openConnection(); 
      conn.setRequestMethod("GET"); 
      // read the response 
      InputStream in = new BufferedInputStream(conn.getInputStream()); 
      response = convertStreamToString(in); 
     } catch (MalformedURLException e) { 
      Log.e(TAG, "MalformedURLException: " + e.getMessage()); 
     } catch (ProtocolException e) { 
      Log.e(TAG, "ProtocolException: " + e.getMessage()); 
     } catch (IOException e) { 
      Log.e(TAG, "IOException: " + e.getMessage()); 
     } catch (Exception e) { 
      Log.e(TAG, "Exception: " + e.getMessage()); 
     } 
     return response; 
    } 

    private String convertStreamToString(InputStream is) { 
     BufferedReader reader = new BufferedReader(new InputStreamReader(is)); 
     StringBuilder sb = new StringBuilder(); 

     String line; 
     try { 
      while ((line = reader.readLine()) != null) { 
       sb.append(line).append('\n'); 
      } 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } finally { 
      try { 
       is.close(); 
      } catch (IOException e) { 
       e.printStackTrace(); 
      } 
     } 

     return sb.toString(); 
    } 
}  

Answer 1

あなたはJSONコンテンツを受信する必要がありますが、サーバーがHTMLコンテンツを返しています。

は、サーバーを変更して、コンテンツタイプとしてapplication/jsonを追加します。

Content-type:application/json