해당 MemoActivity.java에서 onClicksave를 하면 MainActivity로 전환되야 하는데 되질 않네요..
finish()말고 intent 사용해서 넘겨야하나요..?
MemoActivity.java
public class MemoActivity extends AppCompatActivity {
    int year, month, date;
    String memo;
    @BindView(R.id.etMemo)
    EditText etMemo;
    @BindView(R.id.memo_save)
    Button memo_save;
    @OnClick(R.id.memo_save)
    public void onClickSave() {
        Calendar calendar = Calendar.getInstance();
        Memo memo = new Memo();
        memo.setYear(calendar.get(Calendar.YEAR));
        memo.setMonth(calendar.get(Calendar.MONTH));
        memo.setDate(calendar.get(Calendar.DATE));
        memo.setMemo(etMemo.getText().toString());
        Realm realm = Realm.getDefaultInstance();
        realm.beginTransaction();
        realm.copyToRealm(memo);
        realm.commitTransaction();
        realm.close();
        finish();
    }
    public static Intent newIntent(Context context, int year, int month, int date, String memo) {
        Intent intent = new Intent(context, MemoActivity.class);
        intent.putExtra("year", year);
        intent.putExtra("month", month);
        intent.putExtra("date", date);
        intent.putExtra("memo", memo);
        return intent;
    }
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_memo);
        Intent intent = getIntent();
        if (intent != null) {
            Calendar calendar = Calendar.getInstance();
            year = intent.getIntExtra( "year", calendar.get( Calendar.YEAR ) );
            month = intent.getIntExtra( "month", calendar.get( Calendar.MONTH ) );
            date = intent.getIntExtra( "date", calendar.get( Calendar.DATE ) );
            memo = intent.getStringExtra( "memo" );
            if (!TextUtils.isEmpty( memo ))
                etMemo.setText( memo );
        }
    }
}