如何从ObservableValue获得呼叫者舞台？扩展Boolean＆gt;在焦点更改听众

Question

我想将焦点侦听器作为传递静态方法的静态变量，其功能是关闭一个丢失该阶段的阶段。

我有代码：

主类

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception {
        FXMLLoader loader = new FXMLLoader(getClass().getResource("sample.fxml"));
        Scene scene = new Scene(loader.load(), 565, 551);
        primaryStage.setScene(scene);
        Controller controller = loader.getController();
        primaryStage.show();
        controller.setStage1InitOwner();
    }

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

控制器类

 public class Controller implements Initializable {
    @FXML
    private AnchorPane anchorPane;

    // stage1 suppose to be a small dialogs
    private final Stage stage1 = new Stage();

    @Override
    public void initialize(URL url, ResourceBundle resourceBundle) {
        stage1.setScene(new Scene(new Pane(new Label("a Dialog")), 200, 200));

        // giving the listener to stage1 from static method
        stage1.focusedProperty().addListener(Prepare.getFocusListener());
        stage1.initStyle(StageStyle.TRANSPARENT);
    }

    public void setStage1InitOwner() {
        stage1.initOwner(anchorPane.getScene().getWindow());
        stage1.show();
    }
}

准备类（内部的静态方法和变量）

  public class Prepare  {
    public static ChangeListener<Boolean> focusListener = new ChangeListener<Boolean>() {
        @Override
        public void changed(ObservableValue<? extends Boolean> observableValue, Boolean aBoolean, Boolean t1) {
            if (!t1) ;
            // get the stage from observableValue and close it when focus is lost.
        }
    };
    public static ChangeListener<Boolean> getFocusListener()
    {
        return focusListener;
    }
}

FXML文件

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.layout.*?>

<AnchorPane fx:id="anchorPane" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="551.0" prefWidth="565.0" style="-fx-background-color: #fffe00;" xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller">
   <children>
   </children>
</AnchorPane>

现在我想从ChangElistener内的可观察值获得呼叫者阶段。 我试图将其施放到布尔普洛蒂（BooleanProperty），然后使用getBean（）

 if (!t1) {
            BooleanProperty booleanProperty = (BooleanProperty) observableValue;
            Stage stage = (Stage) booleanProperty.getBean();
            stage.close();
        }

，但是我得到了以下错误：

    Exception in thread "JavaFX Application Thread" java.lang.ClassCastException: class javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl cannot be cast to class javafx.beans.property.BooleanProperty (javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl and javafx.beans.property.BooleanProperty are in module javafx.base of loader 'app')
    at sample.Prepare$1.changed(Prepare.java:13)
    at sample.Prepare$1.changed(Prepare.java:9)
    at javafx.base/com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:360)
    at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
    at javafx.base/javafx.beans.property.ReadOnlyBooleanPropertyBase.fireValueChangedEvent(ReadOnlyBooleanPropertyBase.java:78)
    at javafx.base/javafx.beans.property.ReadOnlyBooleanWrapper.fireValueChangedEvent(ReadOnlyBooleanWrapper.java:103)
    at javafx.base/javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:111)
    at javafx.base/javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:145)
    at javafx.graphics/javafx.stage.Window.setFocused(Window.java:678)
    at javafx.graphics/javafx.stage.Window$1.setFocused(Window.java:150)
    at javafx.graphics/com.sun.javafx.stage.WindowHelper.setFocused(WindowHelper.java:112)
    at javafx.graphics/com.sun.javafx.stage.WindowPeerListener.changedFocused(WindowPeerListener.java:64)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:126)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:40)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassWindowEventHandler.lambda$handleWindowEvent$4(GlassWindowEventHandler.java:178)
    at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:424)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassWindowEventHandler.handleWindowEvent(GlassWindowEventHandler.java:176)
    at javafx.graphics/com.sun.glass.ui.Window.handleWindowEvent(Window.java:1336)
    at javafx.graphics/com.sun.glass.ui.Window.notifyFocus(Window.java:1315)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:184)
    at java.base/java.lang.Thread.run(Thread.java:833)
Exception in thread "JavaFX Application Thread" java.lang.ClassCastException: class javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl cannot be cast to class javafx.beans.property.BooleanProperty (javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl and javafx.beans.property.BooleanProperty are in module javafx.base of loader 'app')
    at sample.Prepare$1.changed(Prepare.java:13)
    at sample.Prepare$1.changed(Prepare.java:9)
    at javafx.base/com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:360)
    at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
    at javafx.base/javafx.beans.property.ReadOnlyBooleanPropertyBase.fireValueChangedEvent(ReadOnlyBooleanPropertyBase.java:78)
    at javafx.base/javafx.beans.property.ReadOnlyBooleanWrapper.fireValueChangedEvent(ReadOnlyBooleanWrapper.java:103)
    at javafx.base/javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:111)
    at javafx.base/javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:145)
    at javafx.graphics/javafx.stage.Window.setFocused(Window.java:678)
    at javafx.graphics/javafx.stage.Window$1.setFocused(Window.java:150)
    at javafx.graphics/com.sun.javafx.stage.WindowHelper.setFocused(WindowHelper.java:112)
    at javafx.graphics/com.sun.javafx.stage.WindowPeerListener.changedFocused(WindowPeerListener.java:64)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:126)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:40)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassWindowEventHandler.lambda$handleWindowEvent$4(GlassWindowEventHandler.java:178)
    at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:424)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassWindowEventHandler.handleWindowEvent(GlassWindowEventHandler.java:176)
    at javafx.graphics/com.sun.glass.ui.Window.handleWindowEvent(Window.java:1336)
    at javafx.graphics/com.sun.glass.ui.Window.notifyFocus(Window.java:1315)
    at javafx.graphics/com.sun.glass.ui.win.WinWindow._close(Native Method)
    at javafx.graphics/com.sun.glass.ui.Window.close(Window.java:352)
    at javafx.graphics/com.sun.glass.ui.win.WinWindow.close(WinWindow.java:316)
    at javafx.graphics/com.sun.javafx.tk.quantum.WindowStage.lambda$close$4(WindowStage.java:824)
    at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithRenderLock(QuantumToolkit.java:442)
    at javafx.graphics/com.sun.javafx.tk.quantum.WindowStage.close(WindowStage.java:817)
    at javafx.graphics/javafx.stage.Window$12.invalidated(Window.java:1157)
    at javafx.base/javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:110)
    at javafx.base/javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:145)
    at javafx.graphics/javafx.stage.Window.setShowing(Window.java:1190)
    at javafx.graphics/javafx.stage.Window.hide(Window.java:1215)
    at javafx.graphics/com.sun.javafx.stage.WindowCloseRequestHandler.dispatchBubblingEvent(WindowCloseRequestHandler.java:45)
    at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
    at javafx.graphics/com.sun.javafx.stage.WindowPeerListener.closing(WindowPeerListener.java:93)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:147)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:40)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassWindowEventHandler.lambda$handleWindowEvent$4(GlassWindowEventHandler.java:178)
    at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:424)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassWindowEventHandler.handleWindowEvent(GlassWindowEventHandler.java:176)
    at javafx.graphics/com.sun.glass.ui.Window.handleWindowEvent(Window.java:1336)
    at javafx.graphics/com.sun.glass.ui.Window.notifyClose(Window.java:1241)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:184)
    at java.base/java.lang.Thread.run(Thread.java:833)

那是什么问题，什么是获得舞台的最佳方法。

预先感谢Stackoverflow团队。

Answer 1

错误告诉您有什么问题：

  java.lang.classcastException：javafx.beans.beans.property.readonlybooleanwrapper $ readonlypropertyimpl不能被施加到类中。
 

您正在尝试将readonlybooleanproperty实例施加到booleanproperty，这显然是不可能的。但是您实际上不需要处理这种“狭窄”的实现。您所关心的只是获得“ bean”，只需要类型为a readonlyproperty＆lt;？＆gt; （哪个是属性类层次结构的顶部）。

ChangeListener<Boolean> listener = (obs, wasFocused, isFocused) -> {
  if (!isFocused) {
    var property = (ReadOnlyProperty<?>) obs;
    var stage = (Stage) property.getBean();
    stage.close();
  }
};

但是，您根本不需要处理铸造。如果您的目标是简单地避免代码重复，则只需创建一个接受阶段的实用程序方法，然后将侦听器添加到其fosited属性中即可。

例如：

import javafx.beans.value.ChangeListener;
import javafx.stage.Stage;

public final class CloseOnFocusLost {

  private static final Object KEY = new Object();

  public static void installListener(Stage stage) {
    @SuppressWarnings("unchecked")
    var listener = (ChangeListener<Boolean>) stage.getProperties().get(KEY);
    if (listener == null) {
      listener = (obs, wasFocused, isFocused) -> {
        if (!isFocused) {
          stage.close();
        }
      };
      stage.getProperties().put(KEY, listener);
      stage.focusedProperty().addListener(listener):
    }
  }

  public static void uninstallListener(Stage stage) {
    @SuppressWarnings("unchecked")
    var listener = (ChangeListener<Boolean>) stage.getProperties().remove(KEY);
    if (listener != null) {
      stage.focusedProperty().removeListener(listener):
    }
  }

  // prevent instantiation of utility class
  private CloseOnFocusLost() {}
}

上面的代码具有一些优点：

• 它更加类型安全。
  • 您的代码很容易受到 second classcastException，因为可以将侦听器添加到不属于stage> stage的属性中。<<<<<<<<<<<<<<<< /li>
• 您无需处理铸造，因为您可以直接访问阶段实例。
• 它具有保障措施，以防止将多个侦听器添加到相同的copited属性。

如果您不在乎最后一点，并且永远不需要删除听众，那么您可以将代码简化为以下内容：

import javafx.stage.Stage;

public final class CloseOnFocusLost {

  public static void installListener(Stage stage) {
    stage.focusedProperty().addListener((obs, wasFocused, isFocused) -> {
      if (!isFocused) {
        stage.close();
      }
    });
  }

  // prevent instantiation of utility class
  private CloseOnFocusLost() {}
}

无论哪种情况，您都会添加带有封闭式的失调的听众：

CloseOnFocusLost.installListener(theStageInstance);

Answer 2

一个简单的可执行应用程序，该应用程序从

在此示例中，只有最后一个选项可以通过编程表明确保侦听器不会多次添加到同一阶段。

import javafx.application.Application;
import javafx.beans.property.ReadOnlyProperty;
import javafx.beans.value.ChangeListener;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.stage.Stage;

public class StageClosureApp extends Application {
    private static final ChangeListener<Boolean> CLOSE_ON_FOCUS_LOSS_USING_BEAN_LISTENER =
            (o, wasFocused, isFocused) -> {
                if (!isFocused) ((Stage) ((ReadOnlyProperty<?>) o).getBean()).close();
            };

    private static ChangeListener<Boolean> closeOnFocusLossListener(Stage stage) {
        return (o, wasFocused, isFocused) -> {
            if (!isFocused) stage.close();
        };
    }

    private static void closeOnFocusLoss(Stage stage) {
        stage.focusedProperty().removeListener(CLOSE_ON_FOCUS_LOSS_USING_BEAN_LISTENER);
        stage.focusedProperty().addListener(CLOSE_ON_FOCUS_LOSS_USING_BEAN_LISTENER);
    }

    @Override
    public void start(Stage stage) {
        // all options perform the same function (close the stage on losing focus).
        // when testing, only enable one option, commenting the others out.

        // option 1: use a closure to reference the stage in a lambda function defined inline.
        stage.focusedProperty().addListener((o, wasFocused, isFocused) -> {
            if (!isFocused) stage.close();
        });

        // option 2: pass the stage instance to a static listener generation function.
        stage.focusedProperty().addListener(closeOnFocusLossListener(stage));

        // option 3: get the stage from the bean in an inline lambda function.
        stage.focusedProperty().addListener((o, wasFocused, isFocused) -> {
            if (!isFocused) ((Stage) ((ReadOnlyProperty<?>) o).getBean()).close();
        });

        // option 4: use a single instance static change listener that get the stage from the bean.
        stage.focusedProperty().addListener(CLOSE_ON_FOCUS_LOSS_USING_BEAN_LISTENER);

        // option 5: update stage to add a focus loss listener when it is not focused (can safely be called multiple time for a stage)
        closeOnFocusLoss(stage);
            
        stage.setScene(new Scene(new Label("hello, world")));
        stage.show();
    }
    
    public static void main(String[] args) {
        launch();
    }
}

如果阶段失去焦点是应用程序中显示的唯一阶段（如在这些测试用例中），则默认情况下，该应用程序将自动关闭，根据应用程序生命周期，一旦关注阶段就丢失了。

我不确定这个示例会增加Slaw的答案，但这可能很有用，因此我将暂时保留该帖子。