Android and JSON --- simple example

use org.json.* package

Android Example - Names

Want to return the following JSON string from
A web request (you app must ask for Internet permission) for URL of JSON file (but, could be returned from a Web app)

[{"firstname":"Roger","lastname":"Whitney"},
{"firstname":"Robert","lastname":"Edwards"},
{"firstname":"Kris","lastname":"Stewart"}]

public class NameList extends ListActivity {
 	  public void onCreate(Bundle savedInstanceState) {
 	  super.onCreate(savedInstanceState);
 	  setContentView(R.layout.main);
 	  setListAdapter(new ArrayAdapter<String>(this,
 	  android.R.layout.simple_list_item_1, this.fetchNetworkData()));
 	  }


public ArrayList<String> fetchNetworkData() {
    ArrayList<String> names = new ArrayList<String>();
    try {
        URL dataSource = new URL("http://Server.com/names.json");       //REQUEST JSON FILE ACROSS WEB
        URLConnection dataConnection = dataSource.openConnection();
        BufferedReader in = new BufferedReader(new InputStreamReader(dataConnection.getInputStream()));
        String line = in.readLine();      //READ CONTENTS OF A LINE FROM THE JSON FILE
        
        JSONArray dataArray = new JSONArray(line);         //Convert the String to an org.json.JSONArray object 
        for (int k = 0; k < dataArray.length(); k++) {
            JSONObject name = (JSONObject) dataArray.get(k);
            names.add(name.getString("firstname") + " "+ name.getString("lastname"));
        }

    } catch (Exception e) { Log.e("rew", "error", e); }
     

    return names;//return the JSON Object
}

}




NOTE:  the mention of android.R.layout.simple_list_item_1  in the onCreate method above.   This is one of the many pre-built
layouts that come with Android.  It is used for displaying lists ---so you don't have to re-create it in xml.



 




NOTE: android.R.layout.simple_list_item_1 is

<TextView xmlns:android="http://schemas.android.com/apk/res/android" 
       android:id="@android:id/text1" 
       style="?android:attr/listItemFirstLineStyle" 
       android:paddingTop="2dip" 
       android:paddingBottom="3dip" 
       android:layout_width="fill_parent" 
       android:layout_height="wrap_content" /> 

android.R.layout.simple_list_item_2 is 
   
<TwoLineListItem xmlns:android="http://schemas.android.com/apk/res/ 
       android" 
       android:paddingTop="2dip" 
       android:paddingBottom="2dip" 
       android:layout_width="fill_parent" 
       android:layout_height="wrap_content"> 
        <TextView android:id="@android:id/text1" 
       android:layout_width="fill_parent" 
       android:layout_height="wrap_content" 
       style="?android:attr/listItemFirstLineStyle"/> 

        <TextView android:id="@android:id/text2" 
       android:layout_width="fill_parent" 
       android:layout_height="wrap_content" 
       android:layout_below="@android:id/text1" 
       style="?android:attr/listItemSecondLineStyle" /> 
</TwoLineListItem>

AndroidManifest.xml file (asks for Internet permission)    

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
       package="grewe.json_test"
       android:versionCode="1"
       android:versionName="1.0" >

  <uses-sdk android:minSdkVersion="14" />
  <uses-permission android:name="android.permission.INTERNET"/>


   <application
       android:icon="@drawable/ic_launcher"
       android:label="@string/app_name" >
     <activity
          android:label="@string/app_name"
          android:name=".AndroidJSONActivity" >
        <intent-filter >
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
     </activity>
   </application>

</manifest>

A special Note about URLConnection class ---- used above to connect to json file on web

Some people have experienced problems with Emulator and URLConnection class..........Here is a link to one such instance and solutions suggested.

i've had problems using URLConnection directly - with short transfers
i could reproducibly get "SOCKETLOG add_recv_stats 0" log error
messages, accompanied by nothing being delivered to the Android app.
i switched to using Socket or HttpClient, and everything worked fine.
URLConnection should work though IMHO.