Question

我现在正在学习Java 3周，我想知道如何通过使用Listener来获得没有lambdas的ChoiceBox所选项目（只是字符串）的值。我不使用lambdas因为我想了解它背后的内容。我得到了以下代码：

public class Main extends Application {     

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

    @Override                                                  
    public void start(Stage stage) throws Exception {     

        //BAUSTEINE:
        ChoiceBox<String> choiceBox = new ChoiceBox<String>();          
        choiceBox.getItems().addAll("item1", "item2", "item3");     
        choiceBox.setValue("item1");                                    

        choiceBox.getSelectionModel().selectedItemProperty().addListener()

        //THIS IS THE PLACE FOR THE LISTENER CODE WHICH I NEED ;)


        //LAYOUT:
        VBox vBox = new VBox();
        vBox.setPadding(new Insets(20,20,20,20));
        vBox.setSpacing(10);
        vBox.getChildren().addAll(choiceBox);                   

        //EIGENSCHAFTEN DER SCENE:
        Scene scene = new Scene(vBox, 300, 250);

        //EIGENSCHAFTEN DER STAGE:
        stage.setScene(scene);

        //PROGRAMMSTART:
        stage.show();                                     
    }
}

Answer 1

这三者完全相同：

  choiceBox.getSelectionModel().selectedItemProperty().addListener(new ChangeListener<String>()
  {
     @Override
     public void changed(ObservableValue<? extends String> observable, String oldValue, String newValue)
     {
        System.out.println(observable + oldValue + newValue);
     }
  });

  choiceBox.getSelectionModel().selectedItemProperty().addListener((observable, oldValue, newValue) -> {
     System.out.println(observable + oldValue + newValue);
  });

  choiceBox.getSelectionModel().selectedItemProperty().addListener((observable, oldValue, newValue) -> System.out.println(observable + oldValue + newValue));

JavaFX - 获取没有Lambdas的ChoiceBox的值

1 个答案: