JavaFX ComboBox
Jakob Jenkov |
The JavaFX ComboBox control enables users to choose an option from a predefined list of choices, or type in another
value if none of the predefined choices matches what the user want to select. The
JavaFX ComboBox control is represented by the class javafx.scene.control.ComboBox
. This
JavaFX ComboBox tutorial will explain how to use the ComboBox
class.
Creating a ComboBox
You create a ComboBox
simply by creating a new instance of the ComboBox
class.
Here is a JavaFX ComboBox
instantiation example:
ComboBox comboBox = new ComboBox();
Adding Choices to a ComboBox
You can add choices to a ComboBox
by obtaining its item collection and add items to it.
Here is an example that adds choices to a JavaFX ComboBox
:
comboBox.getItems().add("Choice 1"); comboBox.getItems().add("Choice 2"); comboBox.getItems().add("Choice 3");
Adding a ComboBox to the Scene Graph
To make a ComboBox
visible you must add it to the scene graph. This means that you must add
the ComboBox
to a Scene
object or to some layout component which is then attached
to the Scene
object.
Here is an example showing how to add a JavaFX ComboBox
to the scene graph:
package com.jenkov.javafx.controls; import javafx.application.Application; import javafx.scene.Scene; import javafx.scene.control.ComboBox; import javafx.scene.layout.HBox; import javafx.stage.Stage; public class ComboBoxExperiments extends Application { @Override public void start(Stage primaryStage) throws Exception { primaryStage.setTitle("ComboBox Experiment 1"); ComboBox comboBox = new ComboBox(); comboBox.getItems().add("Choice 1"); comboBox.getItems().add("Choice 2"); comboBox.getItems().add("Choice 3"); HBox hbox = new HBox(comboBox); Scene scene = new Scene(hbox, 200, 120); primaryStage.setScene(scene); primaryStage.show(); } public static void main(String[] args) { Application.launch(args); } }
The application resulting from running this example would look similar to this:
Making the ComboBox Editable
A ComboBox
is not editable by default. That means, that by default the user cannot enter anything
themselves, but only choose from the predefined list of options. To make a ComboBox
editable you
must call the setEditable()
method of the ComboBox
. Here is an example making a
JavaFX ComboBox
editable:
comboBox.setEditable(true);
Once the ComboBox
is editable the user can type in values into the ComboBox
.
The entered value is also read via the getValue()
method as explained earlier.
The following screenthot shows a JavaFX ComboBox
which is editable, and with a custom value
entered:
Reading the Selected Value
You can read the selected value of a ComboBox
via its getValue()
method. If no
choice is selected, the getValue()
method returns null
. Here is an example of calling
getValue()
:
String value = (String) comboBox.getValue();
Listening for Selection
It is possible to listen for selection changes in a JavaFX ComboBox by setting an action listener on the
ComboBox via its setOnAction()
method. Here is an example of setting an action listener on a ComboBox
which reads what value was selected in the ComboBox:
ComboBox comboBox = new ComboBox(); comboBox.getItems().add("Choice 1"); comboBox.getItems().add("Choice 2"); comboBox.getItems().add("Choice 3"); comboBox.setOnAction((event) -> { int selectedIndex = comboBox.getSelectionModel().getSelectedIndex(); Object selectedItem = comboBox.getSelectionModel().getSelectedItem(); System.out.println("Selection made: [" + selectedIndex + "] " + selectedItem); System.out.println(" ComboBox.getValue(): " + comboBox.getValue()); });
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Jakob Jenkov |