如何在场景图的节点中侦听WindowEvent.WINDOW_SHON

Question

WindowEvent.WINDOW_SHOWN似乎从未被调度到场景图中的任何节点上，也没有（我能找到的）知道节点何时可见/渲染/显示。例如：

TestLauncher.java

package com.example.javafx.event;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class TestLauncher extends Application
{
    public static void main(String[] args)
    {
        Application.launch(TestLauncher.class, args);
    }
    @Override
    public void start(Stage stage) throws Exception
    {
        Parent root = FXMLLoader.load(TestController.class.getResource("TestView.fxml"));
        Scene scene = new Scene(root);
        stage.setScene(scene);
        stage.show();
    }
}

TestController.java

package com.example.javafx.event;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.event.EventHandler;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.Parent;
import javafx.scene.control.TextField;
import javafx.stage.WindowEvent;
public class TestController implements Initializable
{
    @FXML private Parent root;
    @FXML private TextField serverAddressInput;
    @FXML private TextField usernameInput;
    @Override
    public void initialize(URL url, ResourceBundle rb)
    {
        serverAddressInput.setText("127.0.0.1");
        //won't work because stage isn't visible yet
        trySetFocusOnUsernameInput1();
        //apparently Stage never passes on any WindowEvents to the children...
        trySetFocusOnUsernameInput2();
    }
    private void trySetFocusOnUsernameInput1()
    {
        usernameInput.requestFocus();
    }
    private void trySetFocusOnUsernameInput2()
    {
        root.addEventFilter(WindowEvent.WINDOW_SHOWN, new EventHandler<WindowEvent>()
        {
            @Override
            public void handle(WindowEvent window)
            {
                usernameInput.requestFocus();
            }
        });
        root.addEventHandler(WindowEvent.WINDOW_SHOWN, new EventHandler<WindowEvent>()
        {
            @Override
            public void handle(WindowEvent window)
            {
                usernameInput.requestFocus();
            }
        });
    }
    public void handleWindowShownEvent()
    {
        usernameInput.requestFocus();
    }
}

TestView.fxml

<?xml version="1.0" encoding="UTF-8"?>
<?import java.lang.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<VBox
    xmlns:fx="http://javafx.com/fxml"
    fx:id="root"
    fx:controller="com.example.javafx.event.TestController"
    prefHeight="150"
    prefWidth="200"
>
    <children>
        <TextField fx:id="serverAddressInput" />
        <TextField fx:id="usernameInput" />
    </children>
</VBox>

那么，实际上，节点如何才能意识到它是可见/呈现/显示的呢？

Answer 1

我想其中一个可能的解决方案是将以下方法添加到TestController.java

    public void handleWindowShownEvent()
    {
        usernameInput.requestFocus();
    }

然后将TestLauncher中的start方法更改为以下方法：

    @Override
    public void start(Stage stage) throws Exception
    {
        FXMLLoader loader = new FXMLLoader();
        Parent root = (Parent)loader.load(TestController.class.getResourceAsStream("TestView.fxml"));
        final TestController controller = (TestController)loader.getController();
        stage.addEventHandler(WindowEvent.WINDOW_SHOWN, new EventHandler<WindowEvent>()
        {
            @Override
            public void handle(WindowEvent window)
            {
                controller.handleWindowShownEvent();
            }
        });
        Scene scene = new Scene(root);
        stage.setScene(scene);
        stage.show();
    }

我真的很欢迎其他解决方案，因为这个方案看起来太笨重了。。。

Answer 2

另一个公认不太性感但将节点与应用程序解耦的解决方案：

root.sceneProperty().addListener(new ChangeListener<Scene>() {
  @Override
  public void changed(ObservableValue<? extends Scene> observable, Scene oldValue, Scene newValue) {
    newValue.windowProperty().addListener(new ChangeListener<Window>() {
      @Override
      public void changed(ObservableValue<? extends Window> observable, Window oldValue, Window newValue) {
        newValue.addEventHandler(WindowEvent.WINDOW_SHOWN, new EventHandler<WindowEvent>() {
          @Override
          public void handle(WindowEvent event) {
            usernameInput.requestFocus();
          }
        });
      }
    });
  }
});

对我来说更有意义。