尽管使用了自定义单元工厂，带有自定义对象的Javafx组合框仍显示对象地址 [英] Javafx combobox with custom object displays object address though custom cell factory is used

问题描述

我有一个组合框，其中显示 User 对象的列表。我已经为组合框编码了一个自定义单元工厂：

I have a combobox which shows list of User objects. I have coded a custom cell factory for the combobox:

@FXML ComboBox<User> cmbUserIds;
cmbUserIds.setCellFactory(new Callback<ListView<User>,ListCell<User>>(){
                @Override
                public ListCell<User> call(ListView<User> l){
                    return new ListCell<User>(){
                        @Override
                        protected void updateItem(Useritem, boolean empty) {
                            super.updateItem(item, empty);
                            if (item == null || empty) {
                                setGraphic(null);
                            } else {
                                setText(item.getId()+"    "+item.getName());
                            }
                        }
                    } ;
                }
            });

ListView显示一个字符串（id +名称），但是当我从listview中选择一个项目时，组合框显示toString（）方法的返回值，即对象的地址。
我无法覆盖toString（）方法，因为User域对象应该与服务器上的对象相同。
如何在组合框中显示ID？请建议

ListView is showing a string(id+name), but when I select an item from listview, Combobox is showing toString() method return value i.e address of object. I can't override toString() method, because the User domain object should be same as the one at server. How to display id in combobox? Please suggest

EDIT1

我尝试了以下代码。现在，当我从列表视图中选择一个值时，组合框显示id。

I tried below code. Now combo box shows id when I select a value from the listview.

cmbUserIds.setConverter(new StringConverter<User>() {
              @Override
              public String toString(User user) {
                if (user== null){
                  return null;
                } else {
                  return user.getId();
                }
              }

            @Override
            public User fromString(String id) {
                return null;
            }
        });

当失去控制焦点时，将清除组合框中的所选值。如何解决此问题？

The selected value in combo box is cleared when control focus is lost. How to fix this?

EDIT2：

@FXML AnchorPane root;
@FXML ComboBox<UserDTO> cmbUsers;
List<UserDTO> users;
public class GateInController implements Initializable {
@Override   
public void initialize(URL location, ResourceBundle resources) {
        users = UserService.getListOfUsers();
        cmbUsers.setItems(FXCollections.observableList(users));
        cmbUsers.getSelectionModel().selectFirst();
        // list of values showed in combo box drop down
        cmbUsers.setCellFactory(new Callback<ListView<UserDTO>,ListCell<UserDTO>>(){
            @Override
            public ListCell<UserDTO> call(ListView<UserDTO> l){
                return new ListCell<UserDTO>(){
                    @Override
                    protected void updateItem(UserDTO item, boolean empty) {
                        super.updateItem(item, empty);
                        if (item == null || empty) {
                            setGraphic(null);
                        } else {
                            setText(item.getUserId()+"    "+item.getUserNm());
                        }
                    }
                } ;
            }
        });
        //selected value showed in combo box
        cmbUsers.setConverter(new StringConverter<UserDTO>() {
              @Override
              public String toString(UserDTO user) {
                if (user == null){
                  return null;
                } else {
                  return user.getUserId();
                }
              }

            @Override
            public UserDTO fromString(String userId) {
                return null;
            }
        });
    }
}

推荐答案

创建并设置 CallBack 如下：

@FXML ComboBox<User> cmbUserIds;

Callback<ListView<User>, ListCell<User>> cellFactory = new Callback<ListView<User>, ListCell<User>>() {

    @Override
    public ListCell<User> call(ListView<User> l) {
        return new ListCell<User>() {

            @Override
            protected void updateItem(User item, boolean empty) {
                super.updateItem(item, empty);
                if (item == null || empty) {
                    setGraphic(null);
                } else {
                    setText(item.getId() + "    " + item.getName());
                }
            }
        } ;
    }
}

// Just set the button cell here:
cmbUserIds.setButtonCell(cellFactory.call(null));
cmbUserIds.setCellFactory(cellFactory);

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