Java从UserList和setItems ComboBox获取用户名

Question

I have this:

@FXML
private ChoiceBox<String> choiseData;

ObservableList<String> choiseUserList = FXCollections.observableArrayList();
ObservableList<User> userList = FXCollections.observableArrayList();    
AdminSQL sql = new AdminSQL();
userList = sql.getAllUser();

for (User u : userList)
choiseUserList.add(u.getUserLogin());
choiseData.setItems(choiseUserList);

I do not like the two list and the loop. I wonder if you can only download users' logins directly from the userList list and place them ChoiseBox

Class User:

private IntegerProperty userLp;
private StringProperty userLogin;
private StringProperty userRule;

Answer 1

Most probably, you don't want to have the ChoiceBox items as a list that's mapped once (somehow) from the real items because doing so comes with a handful of disadvantages:

• the two lists can get easily out off sync: when the users change or any its properties, the ChoiceBox is not updated
• when listening to fi selection changes in the ChoiceBox, the listener doesn't have the complete information about the user (from the selectedItem) but just one of its property values - if it wants to act on the user, it would have to look it up the info somewhere else, thus introducing (unwanted) coupling
• you are fighting the winds of fx, which has dedicated support to configure visual representations of any data object - in the case of a ChoiceBox you'd need a StringConverter

Example code snippet:

ChoiceBox<User> choiceBox =  new ChoiceBox<>(getUsers()); 
    // from your snippet, AdminSQL already returns the list as
    // an ObservableList, so you can set it directly as provided
    // new ChoiceBox<>(sql.getAllUsers()); 
StringConverter<User> converter = new StringConverter<>() {

    @Override
    public String toString(User user) {
        return user != null ? user.getUserLogin() : "";
    }

    @Override
    public User fromString(String userLogin) {
        // should never happen, choicebox is not editable
        throw new UnsupportedOperationException("back conversion not supported from " + userLogin);
    }

};
choiceBox.setConverter(converter);

Answer 2

使用Java 8流

choiseData.getItems().addAll(userList.stream().map(User::getUserLogin()));