public class RegistrationActivity extends AppCompatActivity {

    private EditText editEmailRegistration, editPassRegistration;
    private Button сheck_in, cancel;
    DBHelper dbHelper;

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

        final Intent intentLogin = new Intent(this, LoginActivity.class);

        dbHelper = new DBHelper(this);
        final SQLiteDatabase datebase = dbHelper.getWritableDatabase();
        final ContentValues contentValues = new ContentValues();

        сheck_in = (Button) findViewById(R.id.сheck_in);
        cancel = (Button) findViewById(R.id.cancel);

        editEmailRegistration = (EditText) findViewById(R.id.editEmailRegistration);
        editPassRegistration = (EditText) findViewById(R.id.editPassRegistration);

        cancel.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(intentLogin);
            }
        });


        сheck_in.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (editEmailRegistration.getText().toString().isEmpty()
                        || editPassRegistration.getText().toString().isEmpty()) {
                    throw new IllegalArgumentException("nothing ");
                } else {
                    Cursor cursor = datebase.query(DBHelper.TABLE_CONTACT, null, null, null, null, null, null);
                    contentValues.put(DBHelper.KEY_LOGIN, editEmailRegistration.getText().toString());
                    contentValues.put(DBHelper.KEY_PASS, editPassRegistration.getText().toString());
                    long rowID = datebase.insert(DBHelper.TABLE_CONTACT, null, contentValues);
                    Log.d(DBHelper.DATEBASE_NAME, "row inserted, ID = " + rowID);

                    datebase.insert(DBHelper.TABLE_CONTACT, null, contentValues);
                    cursor.close();
                }

            }
        });

    }

}