JavaFX ContexMenu

阳光穿透心脏的1/2处 2023-10-15 16:43 4阅读 0赞

The *JavaFX* *ContextMenu* component provides a standard right click menu for JavaFX controls. The JavaFX ContextMenu is represented by the class `javafx.scene.control.ContextMenu`. You create a `ContextMenu` instance and attach it to the JavaFX control you want the `ContextMenu` to be active for. Here is a screenshot of a [JavaFX TextArea][] with a `ContextMenu` attached and shown:

![2ab85d9ae10d4344b2ab942b44ea3ddc.png][]

### Full ContextMenu Example ###

Here is a full JavaFX `ContextMenu` example to give you a quick overview of how using the `ContextMenu` looks

import javafx.application.Application;
    import javafx.scene.Scene;
    import javafx.scene.control.*;
    import javafx.scene.layout.VBox;
    import javafx.stage.Stage;
    
    public class ContextMenuExample extends Application {
    
        public static void main(String[] args) {
            launch(args);
        }
    
        public void start(Stage primaryStage) {
    
            ContextMenu contextMenu = new ContextMenu();
            MenuItem menuItem1 = new MenuItem("Choice 1");
            MenuItem menuItem2 = new MenuItem("Choice 2");
            MenuItem menuItem3 = new MenuItem("Choice 3");
    
            menuItem3.setOnAction((event) -> {
                System.out.println("Choice 3 clicked!");
            });
    
            contextMenu.getItems().addAll(menuItem1,menuItem2,menuItem3);
    
            TextArea textArea = new TextArea();
    
            textArea.setContextMenu(contextMenu);
    
            VBox vBox = new VBox(textArea);
            Scene scene = new Scene(vBox);
    
            primaryStage.setScene(scene);
            primaryStage.setTitle("JavaFX App");
    
            primaryStage.show();
        }
    }

### Create a ContextMenu ###

To use a JavaFX `ContextMenu` you must first create a `ContextMenu` instance. Here is an example of creating a JavaFX `ContextMenu`:

ContextMenu contextMenu = new ContextMenu();

### Add Menu Items to the ContextMenu ###

The `ContextMenu` needs one or more `MenuItem` instances which are displayed in the menu. To detect which menu item was clicked, you add listeners to the `MenuItem` instances. Here is an example of adding `MenuItem` instances to a `ContextMenu`:

ContextMenu contextMenu = new ContextMenu();
    
    MenuItem menuItem1 = new MenuItem("Choice 1");
    MenuItem menuItem2 = new MenuItem("Choice 2");
    MenuItem menuItem3 = new MenuItem("Choice 3");
    
    menuItem3.setOnAction((event) -> {
        System.out.println("Choice 3 clicked!");
    });
    
    contextMenu.getItems().addAll(menuItem1,menuItem2,menuItem3);

Notice how there is an `onAction` listener set on the third `MenuItem`, using `setOnAction()`, passing [Java Lambda Expression][] as listener. If this `MenuItem` is clicked, the action listener is executed.

### Add ContextMenu to JavaFX Control ###

A JavaFX `ContextMenu` needs to be attached to a JavaFX control to be active. You add a `ContextMenu` to a control via the `setContextMenu()` of a JavaFX control. Here is an example of adding a JavaFX `ContextMenu` to a JavaFX control:

TextArea textArea = new TextArea();
    textArea.setContextMenu(contextMenu);

[JavaFX TextArea]: https://jenkov.com/tutorials/javafx/textarea.html
[2ab85d9ae10d4344b2ab942b44ea3ddc.png]: https://img-blog.csdnimg.cn/2ab85d9ae10d4344b2ab942b44ea3ddc.png
[Java Lambda Expression]: https://jenkov.com/java/lambda-expressions.html