JavaFX 2 ComboBox setValue() does not set CB text

问题

My problem is that the selected ComboBox item text is not visible on the screen after selecting it with setValue(). Here are some details: Adding items to my CB:

combo.getItems().add("a");
combo.getItems().add("b");
combo.getItems().add("c");
combo.getItems().add("d");

Afterwards, when Button A is pushed:

combo.setValue(null);

When Button B is pushed:

combo.setValue("a");

Now, if I push Button B first, "a" is shown, thats OK. After that if I push Button A, no text is shown on the ComboBox, thats OK. Then I push B, and the value did not change on the screen. However, if I click on the CB, the row for "a" is highlighted, and combo.getValue() returns "a".

Any suggestions how to handle this?

回答1:

I have the same problem. It looks like a bug. Here is a full working example with a ComboBox that contains Locales:

package org.example;

import java.util.Arrays;
import java.util.List;
import java.util.Locale;

import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ComboBox;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;
import javafx.util.StringConverter;

public final class ComboBoxTest extends Application {
    @Override
    public void start(final Stage stage) throws Exception {
        // Initialize UI
        stage.setTitle("ComboBox Test");
        final HBox root = new HBox(5.0f);
        final ComboBox<Locale> cbLocales = new ComboBox<>();
        cbLocales.setConverter(new StringConverter<Locale>() {
            @Override
            public String toString(final Locale locale) {
                return locale.getDisplayName();
            }

            @Override
            public Locale fromString(String string) {
                throw new UnsupportedOperationException();
            }
        });
        cbLocales.setPrefWidth(250);
        HBox.setMargin(cbLocales, new Insets(10));
        root.getChildren().add(cbLocales);
        final Button btnFill = new Button("Fill");
        HBox.setMargin(btnFill, new Insets(10));
        root.getChildren().add(btnFill);
        final Scene scene = new Scene(root);
        stage.setScene(scene);

        btnFill.setOnMouseClicked(new EventHandler<MouseEvent>() {
            @Override
            public void handle(final MouseEvent event) {
                // Fill with content
                final List<Locale> locales = Arrays.asList(Locale.ENGLISH,
                        Locale.GERMAN, Locale.FRENCH);
                final Locale defaultLocale = locales.get(1);
                // cbLocales.getItems.setAll(locales) doesn't work
                cbLocales.getItems().clear();
                cbLocales.getItems().addAll(locales);
                // Set default locale
                cbLocales.setValue(defaultLocale);
                cbLocales.setPromptText(cbLocales.getConverter().toString(
                        cbLocales.getValue()));
            }
        });

        stage.show();
    }

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

When the ComboBox filled for the first time, all works fine: The ComboBox contains all 3 Locales and the second Locale is set.

After filling a second time, ComboxBox.setValue doesn't work: The ComboBox contains all 3 Locales but the second Locale is not set. No item is selected an no prompt is shown.

I fixed the prompt problem with

// Set default locale
cbLocales.setValue(defaultLocale);
cbLocales.setPromptText(cbLocales.getConverter().toString(
        cbLocales.getValue()));

but it doesn't select the item in the list:

A work around is that:

cbLocales.getSelectionModel().select(defaultLocale);
cbLocales.setPromptText(cbLocales.getConverter().toString(cbLocales.getValue()));

To select the item and set the prompt. But I don't know, if there are athor problems with that (tool tips or similar)

回答2:

When creating a combo box, you must instantiate the ComboBox class and define the items as an observable list, just like other UI controls such as ChoiceBox, ListView, and TableView.

Sample Code :

ObservableList<String> options = 
    FXCollections.observableArrayList("A","B","C","D");

combo.setItems(options);

now results should be as u expected :) (tested on my local machine)

Reference : Combo Box

回答3:

I recognized a strange behavior. It looks like the setItems() should not be done before you set your "value"... Here's some code which works for me:

 ComboBox<String> editableComboBox = new ComboBox<String>(); // <- setting the items here 
                                                             // brings the "bug"
    editableComboBox.setId("combobox_fields" + i);
    String desciption = pair.getDescription();
    editableComboBox.setValue(desciption);
    editableComboBox.setEditable(true); 
    editableComboBox.setItems(FieldType.FIELD_TYPES); // <- here we go!

And here the values..

public static final ObservableList<String> FIELD_TYPES =
            FXCollections.observableArrayList("A", "B", "C",
                                              "D", "E", "F",
                                              "G", "H", "I");

来源：https://stackoverflow.com/questions/13483025/javafx-2-combobox-setvalue-does-not-set-cb-text

标签

java

combobox

javafx-2