问将ComboBox设置为只读，而不禁用使用JavaFX的ComboBox

EN

public class ReadonlyComboSelection extends Application {
    StringProperty fixedValue;
    BooleanProperty readonly;
    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("Read Only ComboBox");

        ObservableList<String> strings = FXCollections.observableArrayList();
        for (int i = 0; i <= 10; i++)
            strings.add("Item " + i);

        // Create the ComboBox with the data
        ComboBox<String> comboBox = new ComboBox<>(strings);
        // initialize the fixed selection
        fixedValue = new SimpleStringProperty(strings.get(3));
        readonly = new SimpleBooleanProperty() {

            @Override
            protected void invalidated() {
                if (get()) {
                    comboBox.valueProperty().bind(fixedValue);
                } else {
                    comboBox.valueProperty().unbind();
                }
                comboBox.getSelectionModel().select(comboBox.getValue());
            }

        };
        readonly.set(true);

        // make sure the selection in the popup is showing the value
        comboBox.setOnShowing(e -> {
            if (comboBox.valueProperty().isBound()) {
                comboBox.getSelectionModel().select(comboBox.getValue());
                if (comboBox.getSkin() instanceof ComboBoxListViewSkin skin) {
                    ListView<String> list = (ListView<String>) skin.getPopupContent();
                    list.getSelectionModel().select(comboBox.getValue());
                }
            }
        });

        // just for fun: dynamically change the readonly state
        CheckBox check = new CheckBox("selection is readonly");
        check.selectedProperty().bindBidirectional(readonly);

        HBox layout = new HBox(10, comboBox, check);

        Scene scene = new Scene(layout, 300, 250);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}

//Value to track read only mode
Boolean readOnlyMode = true;

//Values to help revert the selection
int defaultSelection = 3;
//We use a flag so that the message is not displayed twice when we reset the selection
//You can remove then need for this by checking the item that was selected instead and only show the message if it was not te default item
boolean flagToggle = false;

//Add an event to revert the selection and show a message
comboBox.setOnAction((ActionEvent t) ->
{
    if(readOnlyMode){
        //Code here to show a message and revert the selection
        if(!flagToggle){
            //Replace this line with your pop up dialogue, etc
            System.out.println("The application is in Read Only mode");
            //flip the flag for displaying the message
            flagToggle = true;
        }
        //restore the flag
        else{
            flagToggle = false;
        }

        //reset the selection to default, if the selection is already back to the default then this will not trigger another selection event
        comboBox.getSelectionModel().select(defaultSelection);
    }
    else{
        System.out.println("The application is in Edit mode. Item "+ comboBox.getValue() + " selected.");
        //perform normal actions
        //call some method here?
    }
});

import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.collections.FXCollections;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.ButtonType;
import javafx.scene.control.ComboBox;
import javafx.scene.control.SingleSelectionModel;
import javafx.stage.Stage;

public class ApplicationMain extends Application {

    @Override
    public void start(Stage stage) throws Exception {
        ComboBox<String> combo = new ComboBox<>(FXCollections.observableArrayList("First",
                                                                                  "Second",
                                                                                  "Third",
                                                                                  "Fourth",
                                                                                  "Last"));
        SingleSelectionModel<String> selectionModel = combo.getSelectionModel();
        selectionModel.select(0);
        selectionModel.selectedItemProperty().addListener(new ChangeListener<String>() {
            boolean flag = true;
            @Override
            public void changed(ObservableValue<? extends String> observable, String oldValue, String newValue) {
                if (flag) {
                    flag = false;
                    selectionModel.select(oldValue);
                    flag = true;
                    Alert alert = new Alert(AlertType.WARNING, "Read only mode.", ButtonType.CLOSE);
                    alert.setHeaderText(null);
                    alert.showAndWait();
                }
            }
        });
        Group root = new Group(combo);
        Scene scene = new Scene(root, 250.0D, 60.0D);
        stage.setTitle("Example");
        stage.setScene(scene);
        stage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}