ANDROID、WebサーバーからJSONデータを解析してListViewに表示

Question

JSON URLリンクからJSON結果を表示しようとしています。現在、ロードすると何も表示されず、空白のページしか表示されません。 This is the source where I got information about JSON。

この

は私のコードです：

public class DVLAresult extends AppCompatActivity { 


    public class DVLAlist extends ListActivity { 

     @Override 
     protected void onCreate(Bundle savedInstanceState) { 

      super.onCreate(savedInstanceState); 
      setContentView(R.layout.content_dvlaresult); 


      setListAdapter(new ArrayAdapter(
        this,android.R.layout.simple_list_item_2, 
        this.populate())); 
     } 


     private ArrayList<String> populate() { 
      ArrayList<String> items = new ArrayList<String>(); 

      TextView newtext = (TextView) findViewById(R.id.view_number); 

      try { 
       URL url = new URL 
         ("https://dvlasearch.appspot.com/DvlaSearch?licencePlate=mt09nks&apikey=DvlaSearchDemoAccount"); 
       HttpURLConnection urlConnection = 
         (HttpURLConnection) url.openConnection(); 
       urlConnection.setRequestMethod("GET"); 
       urlConnection.connect(); 
       // gets the server json data 
       BufferedReader bufferedReader = 
         new BufferedReader(new InputStreamReader(
           urlConnection.getInputStream())); 
       String next; 
       while ((next = bufferedReader.readLine()) != null) { 
        JSONArray ja = new JSONArray(next); 

        for (int i = 0; i < ja.length(); i++) { 
         JSONObject jo = (JSONObject) ja.get(i); 
         items.add(jo.getString("text")); 
        } 
       } 
      } catch (MalformedURLException e) { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      } catch (IOException e) { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      } catch (JSONException e) { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      } 
      return items; 
     } 
    } 
} 

そして、これは私のXMLファイルsimple_list_2.xml

<?xml version="1.0" encoding="utf-8"?> 

<TwoLineListItem xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:minHeight="?attr/listPreferredItemHeight" 
    android:mode="twoLine" 
    android:paddingStart="?attr/listPreferredItemPaddingStart" 
    android:paddingEnd="?attr/listPreferredItemPaddingEnd"> 

    <TextView android:id="@id/text1" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_marginTop="8dp" 
     android:textAppearance="?attr/textAppearanceListItem" /> 

    <TextView android:id="@id/text2" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_below="@id/text1" 
     android:layout_alignStart="@id/text1" 
     android:textAppearance="?attr/textAppearanceListItemSecondary" /> 

    <TextView android:id="@id/text3" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_below="@id/text2" 
     android:layout_alignStart="@id/text2" 
     android:textAppearance="?attr/textAppearanceListItemSecondary" /> 

... Continue up to text18, because I have 18 fields. 

</TwoLineListItem> 

であり、これは私が似て発生したために起こる主なXMLのリストビュー

<ListView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:id="@+id/list" 
     android:layout_alignParentRight="true" 
     android:layout_alignParentEnd="true" 
     android:layout_above="@+id/button2" 
     android:layout_below="@+id/view_number" /> 

Answer 1

です問題。解決策を見つけるのに役立つコードは次のとおりです。これがあなたを助けることを願っています。エミュレータ上

activity_main.xml

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:paddingLeft="@dimen/activity_horizontal_margin" 
    android:paddingRight="@dimen/activity_horizontal_margin" 
    android:paddingTop="@dimen/activity_vertical_margin" 
    android:paddingBottom="@dimen/activity_vertical_margin" 
    tools:context=".MainActivity"> 


    <Button 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="SEND GET REQUEST" 
     android:id="@+id/sendGet" 
     android:onClick="sendGetRequest" 
     android:layout_alignParentStart="true" /> 

    <ScrollView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:id="@+id/scrollView" 
     android:layout_below="@+id/sendGet" 
     android:layout_centerHorizontal="true"> 

     <TextView 
      android:layout_width="fill_parent" 
      android:layout_height="wrap_content" 
      android:text="Response ....." 
      android:id="@+id/showOutput" 
      android:layout_alignEnd="@+id/scrollView" 
      android:layout_marginEnd="34dp" /> 

    </ScrollView> 

</RelativeLayout> 

MainActivity.javaは

import android.app.ProgressDialog; 
import android.content.Context; 
import android.net.Uri; 
import android.os.AsyncTask; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.TextView; 

import com.google.android.gms.appindexing.Action; 

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

import java.io.BufferedReader; 
import java.io.BufferedWriter; 
import java.io.DataOutputStream; 
import java.io.IOException; 
import java.io.InputStreamReader; 
import java.io.OutputStream; 
import java.io.OutputStreamWriter; 
import java.net.HttpURLConnection; 
import java.net.MalformedURLException; 
import java.net.URL; 

public class MainActivity extends AppCompatActivity { 

    private ProgressDialog progress; 
    /** 
    * ATTENTION: This was auto-generated to implement the App Indexing API. 
    * See https://g.co/AppIndexing/AndroidStudio for more information. 
    */ 
// private GoogleApiClient client; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     // ATTENTION: This was auto-generated to implement the App Indexing API. 
     // See https://g.co/AppIndexing/AndroidStudio for more information. 
    //  client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build(); 
    } 

    public void sendGetRequest(View View) { 
     new GetClass(this).execute(); 
    } 

    @Override 
    public void onStart() { 
     super.onStart(); 

     // ATTENTION: This was auto-generated to implement the App Indexing API. 
     // See https://g.co/AppIndexing/AndroidStudio for more information. 
//  client.connect(); 
     Action viewAction = Action.newAction(
       Action.TYPE_VIEW, // TODO: choose an action type. 
       "Main Page", // TODO: Define a title for the content shown. 
       // TODO: If you have web page content that matches this app activity's content, 
       // make sure this auto-generated web page URL is correct. 
       // Otherwise, set the URL to null. 
       Uri.parse("http://host/path"), 
       // TODO: Make sure this auto-generated app deep link URI is correct. 
       Uri.parse("android-app://com.example.gunawardena.get_post_demo/http/host/path") 
     ); 
//  AppIndex.AppIndexApi.start(client, viewAction); 
    } 

    @Override 
    public void onStop() { 
     super.onStop(); 

     // ATTENTION: This was auto-generated to implement the App Indexing API. 
     // See https://g.co/AppIndexing/AndroidStudio for more information. 
     Action viewAction = Action.newAction(
       Action.TYPE_VIEW, // TODO: choose an action type. 
       "Main Page", // TODO: Define a title for the content shown. 
       // TODO: If you have web page content that matches this app activity's content, 
       // make sure this auto-generated web page URL is correct. 
       // Otherwise, set the URL to null. 
       Uri.parse("http://host/path"), 
       // TODO: Make sure this auto-generated app deep link URI is correct. 
       Uri.parse("android-app://com.example.gunawardena.get_post_demo/http/host/path") 
     ); 
     // AppIndex.AppIndexApi.end(client, viewAction); 
     // client.disconnect(); 
    } 

    private class GetClass extends AsyncTask<String, Void, Void> { 

     private final Context context; 

     public GetClass(Context c) { 
      this.context = c; 
     } 

     protected void onPreExecute() { 
      progress = new ProgressDialog(this.context); 
      progress.setMessage("Loading Get Method....."); 
      progress.show(); 
     } 

     @Override 
     protected Void doInBackground(String... params) { 
      try { 

       final TextView outputView = (TextView) findViewById(R.id.showOutput); 
       URL url = new URL("https://dvlasearch.appspot.com/DvlaSearch?licencePlate=mt09nks&apikey=DvlaSearchDemoAccount"); 
       HttpURLConnection connection = (HttpURLConnection) url.openConnection(); 

       connection.setRequestMethod("GET"); 
       connection.setRequestProperty("USER-AGENT", "Mozilla/5.0"); 
       connection.setRequestProperty("ACCEPT-LANGUAGE", "en-US,en;0.5"); 

       int responseCode = connection.getResponseCode(); 

       final StringBuilder output = new StringBuilder("Request URL " + url); 
       output.append(System.getProperty("line.separator") + "Response Code " + responseCode); 
       output.append(System.getProperty("line.separator") + "Type " + "GET"); 
       BufferedReader br = new BufferedReader(new InputStreamReader(connection.getInputStream())); 
       String line = ""; 
       StringBuilder responseOutput = new StringBuilder(); 
       System.out.println("output===============" + br); 
       while ((line = br.readLine()) != null) { 
        responseOutput.append(line); 
       } 
       br.close(); 

       output.append(System.getProperty("line.separator") + "Response " + System.getProperty("line.separator") + System.getProperty("line.separator") + responseOutput.toString()); 

       MainActivity.this.runOnUiThread(new Runnable() { 

        @Override 
        public void run() { 
         outputView.setText(output); 
         progress.dismiss(); 

        } 
       }); 

      } catch (MalformedURLException e) { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      } catch (IOException e) { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      } 
      return null; 
     } 
    } 
} 

出力

HTH

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参考文献：

• How to send HTTP request GET/POST in Java
• Java HttpURLConnection Example to send HTTP GET/POST Requests
• Android POST and GET Request using HttpURLConnection Tutorial