activity signup e controlli DB

[Chry1911]

Salve amici sto sviluppando un'app

ho problemi su database nel senso che riesco a registrare un utente al servizio ma non riesco a fare il controllo per vedere se esso è già registrato....ecco qui le due classi che sto usando per farlo:

/**
 * Created by christian on 27/01/2016.
 */
public class MySQLiteHelper extends SQLiteOpenHelper {
    //database version
    private static final int DATABASE_VERSION = 1;
    //database name
    private static final String DATABASE_NAME = "ToDoNotes";

    public MySQLiteHelper(Context context){
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    /**
     * Metodo per creare la tabella ToDoNotes_Users
     */

    public void onCreate(SQLiteDatabase db){
        String CREATE_TODONOTES_USERS = "CREATE TABLE ToDoNotes_Users (" +
                "name TEXT, "+
                "email TEXT PRIMARY KEY, "+
                "password TEXT)" ;


        db.execSQL(CREATE_TODONOTES_USERS);
    }

    @Override
    /**
     * Il metodo OnUpgrade elimina la tabella se già presente per crearne una nuova
     */

    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
        db.execSQL("DROP TABLE IF EXISTS ToDoNotes_Users");
        this.onCreate(db);
    }
    //Tabella Utenti
    public static final String TABLE_USERS = "ToDoNotes_Users";

    // Colonne tabella utenti
    private static final String name = "name";
    private static final String email = "email";
    private static final String password = "password";
    //private static final String code ="captcha";


    /**
     * Il metodo inserisce gli utenti nella tabella del database
     */
    public void addUser(User u){
    Log.d("Utenti", u.toString());

        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(name, u.getName());
        values.put(email, u.getEmail());
        values.put(password, u.getPassword());

        db.insert(TABLE_USERS, null, values);

        db.close();
    }

    public User ExistingUser(String mail){
        // metodo per vedere se un utente è già registrato
        Log.d("Verifica", email);

        SQLiteDatabase db = this.getReadableDatabase();
        //String sql = "SELECT email from ToDoNotes_Users Where email=?";
        Cursor cursor = db.query(TABLE_USERS, new String[]{name,email,password}, "email = ?", new String[]{mail}, null, null, null, null);
        if(cursor != null)
            cursor.moveToFirst();

        User user = new User();
        user.setName(cursor.getString(0));
        user.setEmail(cursor.getString(1));
        user.setPassword(cursor.getColumnName(2));

        Log.d("verifica", user.toString());
        return user;

    }
}

public class SignupActivity extends AppCompatActivity {
    private static final String TAG = "SignupActivity";

    public User u;
    public String nome, mail, password,conferma;
    EditText email;
    EditText pass;
    EditText name;
    Button button1;
    TextView text1;
    EditText confirm;


    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_signup);
        //ButterKnife.bind(this);

        final MySQLiteHelper db = new MySQLiteHelper(this);


        button1 = (Button) findViewById(R.id.btn_signup);
        text1 = (TextView) findViewById(R.id.link_login);
        email = (EditText) findViewById(R.id.input_email);
        pass = (EditText) findViewById(R.id.input_password);
        name = (EditText) findViewById(R.id.input_name);
        confirm = (EditText)findViewById(R.id.conf_password);



        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                nome = name.getText().toString();
                mail = email.getText().toString();
                password = pass.getText().toString();
                conferma = confirm.getText().toString();

                if (nome.equals("") || password.equals("") || conferma.equals("") || mail.equals("")) {
                    //Toast.makeText(getApplicationContext(), "Campo mancante, reinserire", Toast.LENGTH_LONG).show();
                    final ProgressDialog progressDialog = new ProgressDialog(SignupActivity.this, R.style.AppTheme_Dark_Dialog);
                    progressDialog.setIndeterminate(true);
                    progressDialog.setMessage("Campo mancante, Reinserire..");
                    progressDialog.show();
                    return;
                }

                if (!password.equals(conferma)) {
                    //Toast.makeText(getApplicationContext(), "Le password non coincidono", Toast.LENGTH_LONG).show();
                    final ProgressDialog progressDialog = new ProgressDialog(SignupActivity.this, R.style.AppTheme_Dark_Dialog);
                    progressDialog.setIndeterminate(true);
                    progressDialog.setMessage("Le password non coincidono, reinserire..");
                    progressDialog.show();
                    return;
                }





                else {
                    /*
                        db.ExistingUser(mail);
                        final ProgressDialog progressDialog = new ProgressDialog(SignupActivity.this, R.style.AppTheme_Dark_Dialog);
                        progressDialog.setIndeterminate(true);
                        progressDialog.setMessage("Email già in uso..");
                        progressDialog.show();
*/
                        // Save the Data in Database
                        db.addUser(new User(nome, mail, password));
                        //Toast.makeText(getApplicationContext(), "Account Creato Correttamente ", Toast.LENGTH_LONG).show();
                        final ProgressDialog progressDialog2 = new ProgressDialog(SignupActivity.this, R.style.AppTheme_Dark_Dialog);
                        progressDialog2.setIndeterminate(true);
                        progressDialog2.setMessage("Registrazione Effettuata..");
                        progressDialog2.show();

                }
            Intent intentLogin = new Intent(getApplicationContext(), LoginActivity.class);

            startActivity(intentLogin);
            // Register(context);
        }
        });

        text1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // Finish the registration screen and return to the Login activity
               // finish();

            }
        });


    }

    @Override
    protected void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();


    }

}

poi un'altra domanda....SendEmail che è una libreria java è supportata su android studio??
e poi come si crea un'altra tabella sqlite che usa la mia primary key come foreign key in un'altra tabella che mi servirà per le attivazioni della licenza mandate via mail??