JavaFX ComboBox setItems 触发 onAction 事件

Question

我有一个 FXML 编辑器和一个 Controller ，它在 TreeView 中选择时设置域对象。因此，每次在 TreeView 中选择一个新对象时， Controller 都会解除编辑器中所有控件与前一个对象的绑定(bind)，并绑定(bind)到新域对象的属性。这包括使用 setItems 从 ComboBox 中的域对象设置值。问题在于 setItems 会为项目列表中的每个项目触发 ComboBox 的 onAction 事件处理程序。根据我的理解，onAction 应该定义当用户从 ComboBox 中选择一个条目时触发的代码，而不是当加载 ComboBox 时触发的代码？!
我可以通过使用鼠标释放事件或在 setItems 期间禁用 actionevent 的 bool 信号量来解决此问题。但是，由于我找不到其他人提出这个要求，我想知道是否有更普遍的问题，我最好问问社区。
我在我的 OnAction 事件处理程序中创建了一个异常来打印堆栈跟踪——这帮助我理解了我上面解释的内容。也许这个堆栈跟踪可以帮助您了解发生了什么/出了什么问题。第一行是在 FXML 中链接到 onActionEvent 的方法，堆栈跟踪中的最后一行是 ComboBox 的 setItems 调用:

at com.agiletunes.EditorCtrl.versionSelection(EditorCtrl.java:173)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at sun.reflect.misc.Trampoline.invoke(Unknown Source)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at sun.reflect.misc.MethodUtil.invoke(Unknown Source)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Node.fireEvent(Node.java:8413)
    at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin.handleControlPropertyChanged(ComboBoxListViewSkin.java:179)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase.lambda$registerChangeListener$61(BehaviorSkinBase.java:197)
    at com.sun.javafx.scene.control.MultiplePropertyChangeListenerHandler$1.changed(MultiplePropertyChangeListenerHandler.java:55)
    at javafx.beans.value.WeakChangeListener.changed(WeakChangeListener.java:89)
    at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:361)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
    at javafx.beans.property.ObjectPropertyBase.fireValueChangedEvent(ObjectPropertyBase.java:105)
    at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:112)
    at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:146)
    at javafx.scene.control.ComboBoxBase.setValue(ComboBoxBase.java:150)
    at javafx.scene.control.ComboBox.updateValue(ComboBox.java:463)
    at javafx.scene.control.ComboBox.access$200(ComboBox.java:192)
    at javafx.scene.control.ComboBox$3.changed(ComboBox.java:446)
    at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:361)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
    at javafx.beans.property.ReadOnlyObjectPropertyBase.fireValueChangedEvent(ReadOnlyObjectPropertyBase.java:74)
    at javafx.beans.property.ReadOnlyObjectWrapper.fireValueChangedEvent(ReadOnlyObjectWrapper.java:102)
    at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:112)
    at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:146)
    at javafx.scene.control.SelectionModel.setSelectedItem(SelectionModel.java:102)
    at javafx.scene.control.ComboBox$ComboBoxSelectionModel.lambda$new$154(ComboBox.java:494)
    at com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:137)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
    at javafx.beans.property.ReadOnlyIntegerPropertyBase.fireValueChangedEvent(ReadOnlyIntegerPropertyBase.java:72)
    at javafx.beans.property.ReadOnlyIntegerWrapper.fireValueChangedEvent(ReadOnlyIntegerWrapper.java:102)
    at javafx.beans.property.IntegerPropertyBase.markInvalid(IntegerPropertyBase.java:113)
    at javafx.beans.property.IntegerPropertyBase.set(IntegerPropertyBase.java:147)
    at javafx.scene.control.SelectionModel.setSelectedIndex(SelectionModel.java:68)
    at javafx.scene.control.SingleSelectionModel.updateSelectedIndex(SingleSelectionModel.java:215)
    at javafx.scene.control.SingleSelectionModel.clearSelection(SingleSelectionModel.java:68)
    at javafx.scene.control.SingleSelectionModel.select(SingleSelectionModel.java:144)
    at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin.lambda$createListView$323(ComboBoxListViewSkin.java:484)
    at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:349)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
    at javafx.beans.property.ReadOnlyIntegerPropertyBase.fireValueChangedEvent(ReadOnlyIntegerPropertyBase.java:72)
    at javafx.beans.property.ReadOnlyIntegerWrapper.fireValueChangedEvent(ReadOnlyIntegerWrapper.java:102)
    at javafx.beans.property.IntegerPropertyBase.markInvalid(IntegerPropertyBase.java:113)
    at javafx.beans.property.IntegerPropertyBase.set(IntegerPropertyBase.java:147)
    at javafx.scene.control.SelectionModel.setSelectedIndex(SelectionModel.java:68)
    at javafx.scene.control.MultipleSelectionModelBase.clearSelection(MultipleSelectionModelBase.java:682)
    at javafx.scene.control.ListView$ListViewBitSetSelectionModel.updateDefaultSelection(ListView.java:1481)
    at javafx.scene.control.ListView$ListViewBitSetSelectionModel.updateItemsObserver(ListView.java:1459)
    at javafx.scene.control.ListView$ListViewBitSetSelectionModel.access$1200(ListView.java:1167)
    at javafx.scene.control.ListView$ListViewBitSetSelectionModel$1.invalidated(ListView.java:1197)
    at javafx.beans.WeakInvalidationListener.invalidated(WeakInvalidationListener.java:83)
    at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:349)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
    at javafx.beans.property.ObjectPropertyBase.fireValueChangedEvent(ObjectPropertyBase.java:105)
    at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:112)
    at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:146)
    at javafx.scene.control.ListView.setItems(ListView.java:390)
    at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin.updateListViewItems(ComboBoxListViewSkin.java:222)
    at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin.lambda$new$322(ComboBoxListViewSkin.java:119)
    at javafx.beans.WeakInvalidationListener.invalidated(WeakInvalidationListener.java:83)
    at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:349)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
    at javafx.beans.property.ObjectPropertyBase.fireValueChangedEvent(ObjectPropertyBase.java:105)
    at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:112)
    at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:146)
    at javafx.scene.control.ComboBox.setItems(ComboBox.java:286)
    at com.agiletunes.EditorCtrl.setHierarchicalElement(EditorCtrl.java:120)

提前致谢!

Answer 1

来自Javadoc of onAction

The ComboBox action, which is invoked whenever the ComboBox value property is changed. This may be due to the value property being programmatically changed [or ...]

替换 items 会导致 value 被设置为 null，这可能会导致 onAction 被触发。

您可以在替换 items 时简单地删除 onAction 事件处理程序以防止它被触发或使用您的 bool 方法之一。

EventHandler<ActionEvent> handler = comboBox.getOnAction();
comboBox.setOnAction(null);
comboBox.setItems(FXCollections.observableArrayList("4", "5", "6"));
comboBox.setOnAction(handler);