Android populating a ListView from content in a database

Question

I have this Android Activity code:

package com.problemio;

import java.io.InputStream;
import java.net.Authenticator;
import java.net.HttpURLConnection;
import java.net.PasswordAuthentication;
import java.net.URL;
import java.net.URLEncoder;
import java.util.List;

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

import com.problemio.LoginActivity.DownloadWebPageTask;

import android.app.Activity;
import android.app.ListActivity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.AsyncTask;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class MyProblemsActivity extends ListActivity 
{
    static final String[] COUNTRIES = new String[] {};

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.problem);

        setListAdapter(new ArrayAdapter<String>(this, R.layout.my_problems, COUNTRIES));

        ListView lv = getListView();
        lv.setTextFilterEnabled(true);

        lv.setOnItemClickListener(new OnItemClickListener() 
        {
            public void onItemClick(AdapterView<?> parent, View view,
                int position, long id) 
            {
              // When clicked, show a toast with the TextView text
              Toast.makeText(getApplicationContext(), (( TextView ) view).getText(),
                  Toast.LENGTH_SHORT).show();

              // For now just do something simple like display a responsive message
              Log.d( "MyProblemsActivity" , "A choice was made from the list");
            }
          });        

        // Check if person is logged in
        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences( MyProblemsActivity.this);
        final String user_id = prefs.getString( "user_id" , null ); 

        // If the user is not logged in, send them to log in
        if ( user_id == null )
        {
            Intent loginIntent = new Intent( MyProblemsActivity.this, LoginActivity.class);
            MyProblemsActivity.this.startActivity(loginIntent);         
        }        

        // Go to the database and display a list of problems, all clickable.
        sendFeedback( user_id );   
    }   

    public void sendFeedback(String user_id) 
    {  
        Log.d( "user_id in MyProblemsActivity" , user_id );

        String[] params = new String[] { "http://www.problemio.com/problems/get_users_problems_mobile.php", user_id };

        DownloadWebPageTask task = new DownloadWebPageTask();
        task.execute(params);        
    }              


    public void onItemClick(AdapterView<?> items, View v, int x, long y)
    {
        Log.d( "onItemClick: " , "In the onItemClick method of MyProblemsActivity" );

    }

    public class DownloadWebPageTask extends AsyncTask<String, Void, String> 
    {
        @Override
        protected String doInBackground(String... theParams) 
        {
            Log.d( "MyProblemsActivity" , "in doInBackground method." );

            String myUrl = theParams[0];
            final String user_id = theParams[1];

            Log.d( "Inner myURL: " , myUrl );
            Log.d( "user_id: " , user_id );

            String charset = "UTF-8";           
            String response = null;

            try 
            {               
                String query = String.format("user_id=%s", 
                         URLEncoder.encode(user_id, charset));

                final URL url = new URL( myUrl + "?" + query );

                final HttpURLConnection conn = (HttpURLConnection) url.openConnection();

                conn.setDoOutput(true); 
                conn.setRequestMethod("POST");

                conn.setDoOutput(true);
                conn.setUseCaches(false);

                conn.connect();

                final InputStream is = conn.getInputStream();
                final byte[] buffer = new byte[8196];
                int readCount;
                final StringBuilder builder = new StringBuilder();
                while ((readCount = is.read(buffer)) > -1) 
                {
                    builder.append(new String(buffer, 0, readCount));
                }

                response = builder.toString();      
                Log.d( "After call, response: " , " " + response);
            } 
            catch (Exception e) 
            {
                    Log.d( "Exception: " , "Yup");
                    e.printStackTrace();
            }

            return response;
        }

        @Override
        protected void onPostExecute(String result) 
        {
            Log.d( "Post execute: " , "In the post-execute method: " + result );
            //textView.setText(result);

            if ( result != null && result == "no_such_user")
            {
                Log.d( "Post execute: " , "NOOOT  OKKKK" ); 
                // Show the user a message that they did not enter the right login

                Toast.makeText(getApplicationContext(), "Your email and password do not match out records. Please try again or create and account.", Toast.LENGTH_LONG).show(); 

                //final TextView login_error = (TextView) findViewById(R.id.login_error);

                //textView.setText("My Text Hellosss - wrong login");            



            }
            else
            {
                Log.d( "Post execute: " , "OKKKK, result: " + result );       

                // Unwrap the stuff from the JSON string

                String problem_title = null;
                String problem_id = null;

                try
                {
                    JSONArray obj = new JSONArray(result);
                    JSONObject o = obj.getJSONObject(0);                    

                    Log.d( "Title: " , "" + o.getString("problem_title") );       
                    Log.d( "id: " , "" + o.getString("problem_id") );      

                    problem_title = o.getString("problem_title");
                    problem_id = o.getString("problem_id");
                }
                catch ( Exception e )
                {
                    Log.d( "JSON ERRORZ: " , "some crap happened " + e.getMessage() );
                }

                // Now not sure what to do :)

            }
        }        
    }
}

I am hoping to query a remote database, get a list of items and display them. But I am not sure how to update the screen with that information after I get it back my JSON from the remote server.

Also, my views xml file is this:

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

<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="10dp"
    android:textSize="16sp" >
</TextView>    

But I am not too sure how it needs to be for displaying a list of items that are dynamically fetched from the db.

Thanks!!

Answer 1

Each time you want to add some another data to your listview, use adapter's add method and then call notifyDataSetChanged() method of your adapter, in order to update the changes in UI.