Dustin Gibson

Favors App (Java, Python, SQL)

Favors is a service classifieds mobile app based on user’s location. Users can register or login for the service and post or respond to service classifieds. Users can also approve or disapprove applicants as well as send instant messages.

Code samples are posted at the bottom of this page

Git Link
Latest Android APK (not signed) June 8th, 2016
Client: Java
Server: Python (Django Framework and Twisted), SQL (postgreSQL), Linux

In Progress:

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Server My server hosted using Linux (Ubuntu 12.04). The webserver I used is NGINX with Gunicorn. The backend is built using Django. The messaging uses Python’s Twisted library for sending and receiving TCP packets. Data is stored using the PostgreSQL database.

Data Model (click to enlarge)

Code Details

Object Oriented – My design philosophy for this particular application is to take advantage of design patterns and build code based on re-usability and easy modification. Through out the code base you’ll see numerous design patters such as Singleton, Adapter, Factory, and Facade.

ORM

Async - The application is designed to handle multiple tasks at once. Android provides a very nice thread-safe async package. For an example: the application is able to update a listview while checking for any incoming messages without running into concurrency issues.
Fragments and Activities - The application have two activities: home and user activity. The home activity is bound to the menu object and everywhere else uses the user activity. Inside each activity are fragments. The home activity, for an example, have nearby favors and asssigned favors fragment. Each fragment and activity represents a single class.
Messaging - Due to the demanding nature of instant messaging, the app uses TCP as opposed to HTTP to send and receive instant messages. Having a delay in response or racking up a sizable amount of limited mobile data is unacceptable for a mobile application. The amount of overhead for a HTTP message is large compared to a TCP packet. Sending and receiving messages from a TCP packet is considerably less expensive.

Challenges and Lessons Learned

Since I lack any formal information systems formal training, putting together the server was incredibly difficult.
Resigning the code to go from using a HTTP based messaging model to a TCP based messaging model.
Understanding the lifecycle of fragment and activities as well as how events work in Android.
I professionally use Oracle SQL and used MySQL at school. PostgreSQL had a lot of noticeable differences.
Mobile UI design was a lot more complicated than I thought. I had to constantly redesign the UI to make the application more user friendly.

Code Samples:

Get Favors List (Python)

			
				

def get_favors_list(request):
	json_message = []
	if request.method == 'GET':
		if request.user.is_authenticated():
			try:
				location_zip = request.COOKIES.get('zip')
				session = Session.objects.get(session_key=request.session.session_key)
				user_id = session.get_decoded().get('_auth_user_id')
				existing_user = User.objects.get(pk=user_id)
				existing_profile = models.UserProfile.objects.filter(ldap_user=existing_user)[0]
				nearby_locations = models.LocationDistance.objects.filter(from_location_fk_id=location_zip).order_by('distance')
				onlocation_favors = models.Favor.objects.filter(location_fk_id=location_zip).exclude(creator_fk=existing_profile)
				for nearby_location in nearby_locations:
					try:
						current_city = models.PresetLocation.objects.filter(presetlocation_id=nearby_location.to_location_fk_id)[0]
						current_favors = models.Favor.objects.filter(location_fk_id=nearby_location.to_location_fk).exclude(creator_fk=existing_profile)
						for current_favor in current_favors:
							thumb_images = models.FavorImage.objects.filter(favor_fk=current_favor)
							current_candidate = models.Candidate.objects.filter(favor_fk=current_favor,candidate_fk=existing_profile)
							if thumb_images.exists():
								thumb_image = thumb_images[0]
							else:
								thumb_image = None
							favors_dump = {}
							favors_dump['favorid'] = str(current_favor.favor_id)
							favors_dump['title'] = current_favor.title
							favors_dump['zip'] = str(current_favor.location_fk_id)
							favors_dump['city'] = current_city.city
							favors_dump['state'] = current_city.state
							favors_dump['distance'] = str(nearby_location.distance)
							if current_candidate.exists():
								favors_dump['status'] = current_candidate[0].status
							else:
								favors_dump['status'] = 'None'
							if thumb_image == None:
								favors_dump['thumb'] = 'None'
							else:
								favors_dump['thumb'] = thumb_image.image_path
							favors_dump['date'] = current_favor.date_created.strftime('%B %d, %Y %I:%M %p')
							favors_dump['deadline'] = current_favor.deadline.strftime('%m/%d/%Y %I:%M %p')
							json_message.append(favors_dump)
					except:
						print "ERROR WITH FAVOR LIST"
						traceback.print_exc()
						return HttpResponse("Issue retrieving data")
				current_city = models.PresetLocation.objects.filter(presetlocation_id=location_zip)[0]
				for onlocation_favor in onlocation_favors:
					thumb_images = models.FavorImage.objects.filter(favor_fk=onlocation_favor)
					current_candidate = models.Candidate.objects.filter(favor_fk=onlocation_favor,candidate_fk=existing_profile)
					if thumb_images.exists():
						thumb_image = thumb_images[0]
					else:
						thumb_image = None
					favors_dump = {}
					favors_dump['favorid'] = str(onlocation_favor.favor_id)
					favors_dump['title'] = onlocation_favor.title
					favors_dump['zip'] = str(onlocation_favor.location_fk_id)
					favors_dump['city'] = current_city.city
					favors_dump['state'] = current_city.state
					favors_dump['distance'] = '0'
					if thumb_image == None:
						favors_dump['thumb'] = 'None'
					else:
						favors_dump['thumb'] = thumb_image.image_path
					if current_candidate.exists():
						favors_dump['status'] = current_candidate[0].status
					else:
						favors_dump['status'] = 'None'
					favors_dump['date'] = onlocation_favor.date_created.strftime('%B %d, %Y %I:%M %p')
					favors_dump['deadline'] = onlocation_favor.deadline.strftime('%m/%d/%Y %I:%M %p')
					json_message.append(favors_dump)
				return HttpResponse(json.dumps(json_message))
			except:
				traceback.print_exc()
				return HttpResponse("Issue getting location")
		else:
			return HttpResponse("User not logged in")
	else:
		return HttpResponse("Wrong method")

Register Fragment (Java)

					
package favorsapp.favors.com.favors;

import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.graphics.Color;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentTransaction;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.AutoCompleteTextView;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import favorsapp.favors.com.favors.sync.GetAutoLocationSync;
import favorsapp.favors.com.favors.sync.RegisterSync;

public class RegisterFragment extends Fragment implements OnTaskCompleted {

    private String descriptionText;
    public RegisterSync RegSync;
    private OnFragmentInteractionListener mListener;
    private OnTaskCompleted onTaskCompletedListener;
    private String autoZip;
    private GetAutoLocationSync autoLocationSync;
    protected ArrayAdapter autoAdapter;
    protected AutoCompleteTextView autoLocationText;
    public static HomeActivity.RootFragmentListener rootFragmentListener;
    public String sessionKey;
    public SharedPreferences loginPrefs;

    public static RegisterFragment newInstance() {
        RegisterFragment fragment = new RegisterFragment();
        Bundle args = new Bundle();
        fragment.setArguments(args);
        return fragment;
    }

    public RegisterFragment() {
        onTaskCompletedListener = this;
    }

    public static RegisterFragment newInstance(HomeActivity.RootFragmentListener fl) {
        rootFragmentListener = fl;
        RegisterFragment fragment = new RegisterFragment();
        return fragment;
    }


    private int registerUser() {
        EditText usernameWidget = (EditText) getView().findViewById(R.id.usernameText);
        EditText verifyPasswordWidget = (EditText) getView().findViewById(R.id.verifyPasswordText);
        EditText passwordWidget = (EditText) getView().findViewById(R.id.passwordText);
        EditText emailWidget = (EditText) getView().findViewById(R.id.emailText);
        EditText zipWidget = (EditText) getView().findViewById(R.id.zipcodeText);
        String verifyPasswordText = verifyPasswordWidget.getText().toString();
        String passwordText = passwordWidget.getText().toString();
        String usernameText = usernameWidget.getText().toString();
        String emailText = emailWidget.getText().toString();
        String zipText = zipWidget.getText().toString();
        if ( !(zipWidget.length() < 6 || zipWidget.length() > 6) )
            return PostStatus("Invalid location");
        else if (!(passwordText.length() <= 30))
            return PostStatus("Password must be no more than 30 characters");
        else if(!(usernameText.length() <= 30))
            return PostStatus("Username must be no more than 30 characters");
        else if (!(usernameText.length() >= 4))
            return PostStatus("Username must be more than 4 characters");
        else if(!(passwordText.length() >= 6))
            return PostStatus("Passwords must have 6 or more characters");
        else if(!passwordText.equals(verifyPasswordText))
            return PostStatus("Password do not match");
        Button registerButton = (Button) getView().findViewById(R.id.registerButton);
        registerButton.setEnabled(false);
        registerButton.setText("Sending...");
        RegSync = new RegisterSync(onTaskCompletedListener);
        RegSync.execute(usernameText, passwordText, emailText, zipText);
        return 1;
    }

    public void goBackHome() {
        FragmentActivity fragActivity = this.getActivity();
        FeedsFragment feedsFragment = (FeedsFragment) fragActivity.getSupportFragmentManager().findFragmentById(R.id.HomeFragment);
        if( feedsFragment == null ) {
           feedsFragment = new FeedsFragment();
            FragmentTransaction feedsTransaction = fragActivity.getSupportFragmentManager().beginTransaction();
            feedsTransaction.replace(R.id.container,feedsFragment);
            feedsTransaction.commit();
        }
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setRetainInstance(true);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View fragmentView = inflater.inflate(R.layout.fragment_register, container, false);
        Button registerButton = (Button) fragmentView.findViewById(R.id.registerButton);
        Button cancelButton = (Button) fragmentView.findViewById(R.id.cancelButton);
        autoLocationText = (AutoCompleteTextView) fragmentView.findViewById(R.id.zipcodeText);
        loginPrefs = getActivity().getSharedPreferences("loginPrefs", Context.MODE_PRIVATE);
        sessionKey = loginPrefs.getString("sessionKey", null);
        registerButton.setOnClickListener (
                new Button.OnClickListener() {
                    public void onClick(View view) {
                        registerUser();
                    }
                });
        cancelButton.setOnClickListener(
                new Button.OnClickListener() {
                    public void onClick(View view) {
                        getActivity().onBackPressed();
                    }
                });
        autoLocationText.addTextChangedListener(new TextWatcher() {
            @Override
            public void afterTextChanged(Editable s) {}

            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {}

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
                autoZip = autoLocationText.getText().toString();
                autoLocationSync = new GetAutoLocationSync(onTaskCompletedListener);
                autoLocationSync.execute(autoZip);
            }

        });
        return fragmentView;
    }

    public void onButtonPressed(Uri uri) {
        if (mListener != null) {
            mListener.onFragmentInteraction(uri);
        }
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            mListener = (OnFragmentInteractionListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }

    public interface OnFragmentInteractionListener {
        public void onFragmentInteraction(Uri uri);
    }

    @Override
    public void onStop() {
        super.onStop();
        if(RegSync != null)
            RegSync.cancel(true);
    }



    public int PostStatus(String status) {
        FragmentActivity currentActivity = this.getActivity();
        TextView descriptionTextView = (TextView)getView().findViewById(R.id.descriptionTextView);
        descriptionText = descriptionTextView.getText().toString();
        switch(status) {
            case "Email and/or Username Exists":
                descriptionText = "Email and/or Username Exists";
                break;

            case "Password Do Not Match":
                descriptionText = "Passwords do not match. Re-enter password...";
                break;

            case "Success":
                descriptionText = "Registered";
                ((UserActivity)this.getActivity()).switchToLogin();
                return 1;

            case "password less than 6 chars":
                descriptionText = "Your password has less than 6 characters. Enter a password 6 characters or more:";
                break;

            case "username less than 4 chars":
                descriptionText = "Your username has less than 4 characters. Enter a username with 4 characters or more:";
                break;

            case "username over 30 chars":
                descriptionText = "Your username has more than 30 characters. Enter a username with less than 30 characters:";
                break;

            case "password over 30 chars":
                descriptionText = "Your password has more than 30 characters. Enter a password with less than 30 characters:";
                break;

            default:
                descriptionText = "Something is wrong with server";
                break;
        }
        descriptionTextView.setTextColor(Color.RED);
        descriptionTextView.setText(descriptionText);
        return 0;
    }

    public void SetAutoComplete(String[] stringArray)
    {
        if(stringArray.length > 0) {
            autoAdapter = new ArrayAdapter(getActivity(),
                    R.layout.list_autolocation,
                    R.id.autolocationText,
                    stringArray);
            autoLocationText.setAdapter(autoAdapter);
            if (!autoLocationText.isPopupShowing())
                autoLocationText.showDropDown();
        }
    }

    public void UpdateUI(String status, String event) {
        PostStatus(status);
        Button registerButton = (Button)getView().findViewById(R.id.registerButton);
        registerButton.setEnabled(true);
        registerButton.setText("Register");
    }

}

Register Async (Java)

				

package favorsapp.favors.com.favors.sync;

import android.os.AsyncTask;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;

import favorsapp.favors.com.favors.OnTaskCompleted;

public class RegisterSync extends AsyncTask {

    protected String status;
    private OnTaskCompleted onTaskCompleted;

    public RegisterSync(OnTaskCompleted onTaskCompleted) {
        this.onTaskCompleted = onTaskCompleted;
    }

    @Override
    protected void onPreExecute() {
    }

    @Override
    protected String doInBackground(String... params) {
        status = "fail";
        try {
            URL registerURL = new URL("http://45.55.133.160/favors/registration.html");
            HttpURLConnection connection = (HttpURLConnection) registerURL.openConnection();
            connection.setDoOutput(true);
            connection.setRequestMethod("POST");
            connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            OutputStreamWriter outWriter = new OutputStreamWriter ( connection.getOutputStream());
            String modZip = params[3].toString().replace("(","").replace(")","").trim();
            modZip = modZip.substring(modZip.length()-5,modZip.length());
            String postString = "";
            postString += "username=" + URLEncoder.encode(params[0]) + "&";
            postString += "password=" + URLEncoder.encode(params[1]) + "&";
            postString += "email=" + URLEncoder.encode(params[2]) + "&";
            postString += "zipcode=" + URLEncoder.encode(modZip);
            outWriter.write(postString);
            outWriter.close();
            if( connection.getResponseCode() == HttpURLConnection.HTTP_OK) {
                BufferedReader br = new BufferedReader(new InputStreamReader(connection.getInputStream()));
                String line;
                while(((line = br.readLine()) != null)) {
                    status = line;
                    return line;
                }
            } else {
                return "fail";
            }
        } catch (MalformedURLException eURL) {
            return "fail";
        } catch (IOException e) {
            e.printStackTrace();
            return "fail";
        }
        return "fail";
    }

    @Override
    protected void onProgressUpdate(String... values) {

    }

    @Override
    protected void onPostExecute(String result) {
        onTaskCompleted.UpdateUI(status,"");
    }
}