Displaying json data into two adjacent listview

Question

I have an app that should parse a json object from a URL and display it into two adjacent listview (the json object itself is a result of a query of MySQL database ) .

I tried with the following code but it seems that I need to AsyncTask class to accomplish this task .

Could someone helps me to write the corresponding AsyncTask class, by guiding me what to write in doinbackground, onPreExecute() ,onPostExecute.

MainActivity

public class MainActivity extends Activity
{


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

    private void connect() 
    {

      String data;
      List<String> r = new ArrayList<String>();

      ArrayAdapter<String>adapter=new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1,r);
      ListView list=(ListView)findViewById(R.id.leftListView);
      ListView list2=(ListView)findViewById(R.id.rightListView);
      list2.setBackgroundColor(Color.BLUE);

        try 

        {
            DefaultHttpClient client = new DefaultHttpClient();
            HttpGet request = new HttpGet("http://192.168.1.16:89/Derdeery/Zaki.php");
            HttpResponse response = client.execute(request);
            HttpEntity entity=response.getEntity();
            data=EntityUtils.toString(entity);
            Log.e("STRING", data);


            try {


       JSONArray json=new JSONArray(data);

       for(int i=0;i<json.length(); i++)
       {

        JSONObject obj=json.getJSONObject(i);
        String name=obj.getString("Part_NAME");
        String id = obj.getString("Part_ID") ;
        Log.e("name", name);
        r.add(name+"-"+id);

        list.setAdapter(adapter);

          }

           } catch (JSONException e) {
       // TODO Auto-generated catch block
       e.printStackTrace();
      }

        } catch (ClientProtocolException e) {
            Log.d("HTTPCLIENT", e.getLocalizedMessage());
        } catch (IOException e) {
            Log.d("HTTPCLIENT", e.getLocalizedMessage());
        }


    }
}

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal">

    <ListView
        android:id="@+id/leftListView"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_margin="2dp"
        android:layout_weight=".75" />

    <ListView
        android:id="@+id/rightListView"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_margin="2dp"
        android:layout_weight=".25" />

</LinearLayout>

Edit: I tried with this code but I get unfortunately app has stopped error.

  public class MainActivity extends Activity {
    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    new GetData().execute();

}


private class GetData extends AsyncTask<Void, Void, Void> 
{
    ProgressDialog progressDialog;
    String data;
    List<String> r = new ArrayList<String>();
    ArrayAdapter<String>adapter=new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1,r);    
    ListView list =  (ListView)findViewById(R.id.right);
    ListView list2= (ListView)findViewById(R.id.left);

    public GetData()
    {


    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        progressDialog = new ProgressDialog(MainActivity.this);


        progressDialog.setCancelable(false);
        if (!progressDialog.isShowing()) {
            progressDialog.show();
        }

    }



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

    {
        DefaultHttpClient client = new DefaultHttpClient();
        HttpGet request = new HttpGet("http://192.168.1.5:89/Derdeery/Zaki.php");
        HttpResponse response = client.execute(request);
        HttpEntity entity=response.getEntity();
        data=EntityUtils.toString(entity);
        Log.e("STRING", data);

    } 
    catch (ClientProtocolException e) 
    {
        Log.d("HTTPCLIENT", e.getLocalizedMessage());
    }
    catch (IOException e) 
    {
        Log.d("HTTPCLIENT", e.getLocalizedMessage());
    }
        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        super.onPostExecute(result);
         try {

        if (progressDialog.isShowing()) {
            progressDialog.dismiss();
        }
           JSONArray json=new JSONArray(data);

           for(int i=0;i<json.length(); i++)
           {

            JSONObject obj=json.getJSONObject(i);
            String name=obj.getString("Part_NAME");
            String id = obj.getString("Part_ID") ;
            Log.e("name", name);
            r.add(name+"-"+id);



            }
            adapter.notifyDataSetChanged();


        } catch (JSONException e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
         }


      }}


         }

Answer 1

Try like This

private class GetData extends AsyncTask<Void, Void, Void> {
    ProgressDialog progressDialog;
    public GetData() {


    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        progressDialog = new ProgressDialog(getActivity());
        progressDialog.setTitle(getResources().getString(
                R.string.progress_title));
        progressDialog.setMessage(getResources().getString(
                R.string.progress_message));
        progressDialog.setCancelable(false);
        if (!progressDialog.isShowing()) {
            progressDialog.show();
        }

    }

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

    {
        DefaultHttpClient client = new DefaultHttpClient();
        HttpGet request = new HttpGet("http://192.168.1.16:89/Derdeery/Zaki.php");
        HttpResponse response = client.execute(request);
        HttpEntity entity=response.getEntity();
        data=EntityUtils.toString(entity);
        Log.e("STRING", data);

    } catch (ClientProtocolException e) {
        Log.d("HTTPCLIENT", e.getLocalizedMessage());
    } catch (IOException e) {
        Log.d("HTTPCLIENT", e.getLocalizedMessage());
    }
        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        super.onPostExecute(result);
         try {

        if (progressDialog.isShowing()) {
            progressDialog.dismiss();
        }
           JSONArray json=new JSONArray(data);

           for(int i=0;i<json.length(); i++)
           {

            JSONObject obj=json.getJSONObject(i);
            String name=obj.getString("Part_NAME");
            String id = obj.getString("Part_ID") ;
            Log.e("name", name);
            r.add(name+"-"+id);



            }
            adapter.notifyDataSetChanged();


        } catch (JSONException e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
         }

    }

Answer 2

I can give you a rough idea:

1.) Perform the network operation i.e. fetching the data from your database (on server side, converting it into json etc) inside doInBackGround().

2.) The doInBackground() will return a result, which will be received by onPostExecute(), inside onPostExecute, set that result on the 2 listviews.

3.) The onPreExecute() will contain the progress dialog logic which will be shown when doInBackground will be running.

Hope you can try once. Let me know otherwise, I will help you further.