public class MainActivity extends AppCompatActivity {
Button loginBtn, registerBtn;
EditText usernameET, passwordET;
TextView forgotTV;
String works = "";

String username, password;

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

    usernameET = (EditText) findViewById(R.id.usernameET);
    passwordET = (EditText) findViewById(R.id.passwordET);


    loginBtn = (Button) findViewById(R.id.loginBtn);
    loginBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            username = usernameET.getText().toString();
            password = passwordET.getText().toString();
            String method = "login";

            BackgroundTask backgroundTask = new
            BackgroundTask(MainActivity.this);
            backgroundTask.execute(method, username, password);

            if(true) {
                Intent intent = new Intent(MainActivity.this, Home.class);
                startActivity(intent);
            }

        }
    });

    registerBtn = (Button) findViewById(R.id.registerBtn);
    registerBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            startActivity(new Intent(MainActivity.this, Register.class));
        }
    });

    forgotTV = (TextView) findViewById(R.id.forgotBtn);
    forgotTV.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            startActivity(new Intent(MainActivity.this,
            ForgotPassword.class));
        }
    });
}

public class BackgroundTask extends AsyncTask<String, Void, String> {
Context context;
AlertDialog alertDialog;

BackgroundTask(Context ctx) {
    context = ctx;
}

@Override
protected String doInBackground(String... params) {
    String registrationURL = "http://192.168.0.15:8080/imo/register.php";
    String loginURL = "http://192.168.0.15:8080/imo/login.php";
    String postURL = "http://192.168.0.15:8080/imo/postbox.php";

    String line = "";
    String result = "";


    String type = params[0];

    if (type.equals("login")) {
        String username = params[1];
        String password = params[2];

        try {
            URL url = new URL(loginURL);
            HttpURLConnection httpURLConnection = (HttpURLConnection)
            url.openConnection();
            httpURLConnection.setRequestMethod("POST");
            httpURLConnection.setDoOutput(true);
            httpURLConnection.setDoInput(true);
            OutputStream OS = httpURLConnection.getOutputStream();
            BufferedWriter writer = new BufferedWriter(new
            OutputStreamWriter(OS, "UTF-8"));
            String postData = URLEncoder.encode("username", "UTF-8") + "=" +
            URLEncoder.encode(username, "UTF-8") + "&"
                    + URLEncoder.encode("password", "UTF-8") + "=" +
            URLEncoder.encode(password, "UTF-8");
            writer.write(postData);
            writer.flush();
            writer.close();
            OS.close();
            InputStream IS = httpURLConnection.getInputStream();
            BufferedReader reader = new BufferedReader(new
            InputStreamReader(IS, "iso-8859-1"));
            while ((line = reader.readLine()) != null) {
                result += line;
            }
            reader.close();
            IS.close();
            httpURLConnection.disconnect();
            return result;

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    } else if (type.equals("register")) {
        String username = params[1];
        String password = params[2];
        String email = params[3];

        try {
            URL url = new URL(registrationURL);
            HttpURLConnection httpURLConnection = (HttpURLConnection)
            url.openConnection();
            httpURLConnection.setRequestMethod("POST");
            httpURLConnection.setDoOutput(true);
            httpURLConnection.setDoInput(true);
            OutputStream OS = httpURLConnection.getOutputStream();
            BufferedWriter writer = new BufferedWriter(new
            OutputStreamWriter(OS, "UTF-8"));
            String postData = URLEncoder.encode("username", "UTF-8") + "=" +
            URLEncoder.encode(username, "UTF-8") + "&"
                    + URLEncoder.encode("password", "UTF-8") + "=" +
            URLEncoder.encode(password, "UTF-8") + "&"
                    + URLEncoder.encode("email", "UTF-8") + "=" +
            URLEncoder.encode(email, "UTF-8");
            writer.write(postData);
            writer.flush();
            writer.close();
            OS.close();
            InputStream IS = httpURLConnection.getInputStream();
            BufferedReader reader = new BufferedReader(new
            InputStreamReader(IS, "iso-8859-1"));
            while ((line = reader.readLine()) != null) {
                result += line;
            }
            reader.close();
            IS.close();
            httpURLConnection.disconnect();
            return result;

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    else if(type.equals("postbox")){
        String body = params[1];

        try {
            URL url = new URL(postURL);
            HttpURLConnection httpURLConnection = (HttpURLConnection)
            url.openConnection();
            httpURLConnection.setRequestMethod("POST");
            httpURLConnection.setDoOutput(true);
            httpURLConnection.setDoInput(true);
            OutputStream OS = httpURLConnection.getOutputStream();
            BufferedWriter writer = new BufferedWriter(new
            OutputStreamWriter(OS, "UTF-8"));
            String postData = URLEncoder.encode("body", "UTF-8") + "=" +
            URLEncoder.encode(body, "UTF-8");
            writer.write(postData);
            writer.flush();
            writer.close();
            OS.close();
            InputStream IS = httpURLConnection.getInputStream();
            BufferedReader reader = new BufferedReader(new
            InputStreamReader(IS, "iso-8859-1"));
            while ((line = reader.readLine()) != null) {
                result += line;
            }
            reader.close();
            IS.close();
            httpURLConnection.disconnect();
            return result;

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    return null;
}


    @Override
    protected void onPreExecute () {
        alertDialog = new AlertDialog.Builder(context).create();
        alertDialog.setTitle("LOG");
    }

    @Override
    protected void onPostExecute (String result){
        alertDialog.setMessage(result);
        alertDialog.show();

    }

    @Override
    protected void onProgressUpdate (Void...values){
        super.onProgressUpdate(values);
    }
}