public class MainActivity extends AppCompatActivity {

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

}

public void userReg(View view){
    startActivity(new Intent(this, Register.class));

}

public void userLogin(View view){

    }
}

public class Register extends Activity {

    EditText etName, etUsername, etPassword;
    String name, user_name, user_pass;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_register);

        etName = (EditText)findViewById(R.id.name);
        etUsername = (EditText)findViewById(R.id.new_user_name);
        etPassword = (EditText)findViewById(R.id.new_user_pass);
    }

    public void userReg(View view){

        name = etName.getText().toString();
        user_name = etUsername.getText().toString();
        user_pass = etPassword.getText().toString();

        String method = "register";
        BackgroundTask backgroundTask = new BackgroundTask(this);
        backgroundTask.execute(method,name,user_name,user_pass);
        finish();

    }
}

public class BackgroundTask extends AsyncTask<String, Void, String> {

    Context ctx;
    BackgroundTask(Context ctx){
        this.ctx = ctx;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected String doInBackground(String... params) {

        String reg_url = "http://10.0.2.2/webapp/register.php";
        String login_url = "http://10.0.2.2/webapp/login.php";
        String method = params[0];
        if (method.equals("register")) {
            String name = params[1];
            String user_name = params[2];
            String user_pass = params[3];
            try {
                URL url = new URL(reg_url);
                HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
                httpURLConnection.setRequestMethod("POST");
                httpURLConnection.setDoOutput(true);
                //httpURLConnection.setDoInput(true);
                OutputStream OS = httpURLConnection.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(OS, "UTF-8"));
                String data = URLEncoder.encode("user", "UTF-8") + "=" + URLEncoder.encode(name, "UTF-8") + "&" +
                        URLEncoder.encode("user_name", "UTF-8") + "=" + URLEncoder.encode(user_name, "UTF-8") + "&" +
                        URLEncoder.encode("user_pass", "UTF-8") + "=" + URLEncoder.encode(user_pass, "UTF-8");
                bufferedWriter.write(data);
                bufferedWriter.flush();
                bufferedWriter.close();
                OS.close();
                InputStream IS = httpURLConnection.getInputStream();
                IS.close();
                //httpURLConnection.connect();
                httpURLConnection.disconnect();
                return "Registration Success...";
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

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

    @Override
    protected void onPostExecute(String result) {
        Toast.makeText(ctx,result,Toast.LENGTH_LONG).show();
    }
}