在JavaFx中，我向ComboBox對象添加操作後，如何使我的ComboBox可編輯

在JavaFx中，如何在將操作添加到ComboBox對象後使我的ComboBox可編輯。當我這樣做，但我得到一個錯誤，但我得到一個錯誤是缺少的東西。我仍然是Javafx的新手。這裏是代碼。在JavaFx中，我向ComboBox對象添加操作後，如何使我的ComboBox可編輯

我想要做的就是給用戶一些固定的項目來選擇，但首先如果用戶從組合框中選擇其他，組合框然後變得可編輯。從按鈕設置可編輯的combobox工作得很好。我甚至提出了一種方法來影響組合框。如果你瞭解JAVA，請仔細閱讀代碼。

import javafx.application.Application; 
import javafx.geometry.Insets; 
import javafx.scene.Scene; 
import javafx.scene.control.Button; 
import javafx.scene.control.ComboBox; 
import javafx.scene.control.Label; 
import javafx.scene.layout.VBox; 
import javafx.stage.Stage; 

public class main extends Application{ 

    ComboBox<String> cb = new ComboBox<>(); 

    public static void main(String[] args) { 

     launch(args); 
    } 

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

     Button b = new Button("GOOWE"); 

     Label choice = new Label("What type of Vehicle do you drive"); 
     cb.getItems().addAll("Car","Jeep","Bus","Other"); 

     cb.setPromptText("Select your Vehicle"); 

     cb.setOnAction(e ->{ 

      if (cb.getValue().equals("Other")){ 
       //Both the editable and cb.setEditable still give error in the terminal 
       editable(cb); 
       //cb.setEditable(true); 
      } 

     }); 
     VBox layout = new VBox(10); 

     layout.setPadding(new Insets(10,10,10,10)); 
     layout.getChildren().addAll(choice,cb,b); 

     b.setOnAction(e -> { 

     cb.setEditable(true); 

     }); 

     Scene sc = new Scene(layout,200,400); 

     stage.setScene(sc); 

     stage.show(); 

    } 

    private void editable(ComboBox<String> cb2) { 

      cb2.setEditable(true); 

    } 

}

這是錯誤

Exception in thread "JavaFX Application Thread" java.lang.NullPointerException 
    at pk8.main.lambda$0(main.java:44) 
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86) 
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238) 
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191) 
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59) 
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58) 
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) 
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56) 
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) 
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56) 
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) 
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74) 
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49) 
    at javafx.event.Event.fireEvent(Event.java:198) 
    at javafx.scene.Node.fireEvent(Node.java:8413) 
    at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin.handleControlPropertyChanged(ComboBoxListViewSkin.java:179) 
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase.lambda$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.ComboBox.lambda$new$153(ComboBox.java:269) 
    at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:349) 
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81) 
    at javafx.beans.property.BooleanPropertyBase.fireValueChangedEvent(BooleanPropertyBase.java:103) 
    at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:110) 
    at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:144) 
    at javafx.scene.control.ComboBoxBase.setEditable(ComboBoxBase.java:164) 
    at pk8.main.editable(main.java:78) 
    at pk8.main.lambda$0(main.java:46) 
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86) 
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238) 
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191) 
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59) 
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58) 
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) 
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56) 
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) 
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56) 
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) 
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74) 
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49) 
    at javafx.event.Event.fireEvent(Event.java:198) 
    at javafx.scene.Node.fireEvent(Node.java:8413) 
    at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin.handleControlPropertyChanged(ComboBoxListViewSkin.java:179) 
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase.lambda$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.select(SingleSelectionModel.java:149) 
    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.select(MultipleSelectionModelBase.java:404) 
    at javafx.scene.control.MultipleSelectionModelBase.clearAndSelect(MultipleSelectionModelBase.java:356) 
    at javafx.scene.control.ListView$ListViewBitSetSelectionModel.clearAndSelect(ListView.java:1403) 
    at com.sun.javafx.scene.control.behavior.CellBehaviorBase.simpleSelect(CellBehaviorBase.java:256) 
    at com.sun.javafx.scene.control.behavior.CellBehaviorBase.doSelect(CellBehaviorBase.java:220) 
    at com.sun.javafx.scene.control.behavior.CellBehaviorBase.mousePressed(CellBehaviorBase.java:150) 
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:95) 
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89) 
    at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218) 
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80) 
    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.EventUtil.fireEventImpl(EventUtil.java:74) 
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54) 
    at javafx.event.Event.fireEvent(Event.java:198) 
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3757) 
    at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485) 
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762) 
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494) 
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:381) 
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295) 
    at java.security.AccessController.doPrivileged(Native Method) 
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:417) 
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389) 
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:416) 
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555) 
    at com.sun.glass.ui.View.notifyMouse(View.java:937) 
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method) 
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191) 
    at java.lang.Thread.run(Thread.java:748) 
Exception in thread "JavaFX Application Thread" java.lang.IndexOutOfBoundsException 
    at com.sun.javafx.scene.control.ReadOnlyUnbackedObservableList.subList(ReadOnlyUnbackedObservableList.java:136) 
    at javafx.collections.ListChangeListener$Change.getAddedSubList(ListChangeListener.java:242) 
    at com.sun.javafx.scene.control.behavior.ListViewBehavior.lambda$new$177(ListViewBehavior.java:269) 
    at javafx.collections.WeakListChangeListener.onChanged(WeakListChangeListener.java:88) 
    at com.sun.javafx.collections.ListListenerHelper$Generic.fireValueChangedEvent(ListListenerHelper.java:329) 
    at com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(ListListenerHelper.java:73) 
    at com.sun.javafx.scene.control.ReadOnlyUnbackedObservableList.callObservers(ReadOnlyUnbackedObservableList.java:75) 
    at javafx.scene.control.MultipleSelectionModelBase.clearAndSelect(MultipleSelectionModelBase.java:378) 
    at javafx.scene.control.ListView$ListViewBitSetSelectionModel.clearAndSelect(ListView.java:1403) 
    at com.sun.javafx.scene.control.behavior.CellBehaviorBase.simpleSelect(CellBehaviorBase.java:256) 
    at com.sun.javafx.scene.control.behavior.CellBehaviorBase.doSelect(CellBehaviorBase.java:220) 
    at com.sun.javafx.scene.control.behavior.CellBehaviorBase.mousePressed(CellBehaviorBase.java:150) 
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:95) 
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89) 
    at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218) 
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80) 
    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.EventUtil.fireEventImpl(EventUtil.java:74) 
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54) 
    at javafx.event.Event.fireEvent(Event.java:198) 
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3757) 
    at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485) 
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762) 
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494) 
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:381) 
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295) 
    at java.security.AccessController.doPrivileged(Native Method) 
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:417) 
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389) 
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:416) 
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555) 
    at com.sun.glass.ui.View.notifyMouse(View.java:937) 
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method) 
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191) 
    at java.lang.Thread.run(Thread.java:748)

來源

2017-10-18 Jeb Eb

的可能的複製[什麼是一個NullPointerException，以及如何解決它？]（https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it） –

似乎是一個錯誤在fx8，工作正常fx9 – kleopatra

我會升級並看到變化。謝謝@ kleopatra –

基本上，它是在FX8的錯誤：幾乎所有selectionModels受到嚴重破損。對於NPE在你的代碼拋出的確切原因有兩方面：

操作處理程序被調用兩次，在第一次調用組合的價值是「其他」在第二它爲空（榮譽給@M leRutte尋找它） - 這是在外匯中的錯誤
的NPE發生的第二次左右，如您認爲該值不爲空與if (cb.getValue().equals("Other")) - 這種檢查能更好地處理倒過來，就是if ("Other".equals(cb.getValue()))

但是：即使使用反轉檢查，設置可編輯性也會在帶有IndexOutOfBounds的fx8中拋出。原因是嚴重的MultipleSelectionModelBase的破壞實現（在fx9中改進）。如果可能，升級。

如果不可能，即使在fx8中也有辦法解決：只有在彈出窗口打開時修改editable屬性時纔會出現錯誤。所以我改變了邏輯

聽取組合的valueProperty和更新編輯只有當沒有顯示
安裝一個事件處理程序，以onHidden來檢查值，並將編輯

仍然有輕微的毛刺：

transfering聚焦到輸入字段需要調整內部
標記v ALUE（AKS「其他」）未在文本框所示，懶得進一步挖掘，可能與該值爲空temporariy

修改後的示例：

public class ComboBoxActionEditable extends Application{ 

    ComboBox<String> cb = new ComboBox<>(); 

    /** 
    * Sets the combo's editable if given value equals the marker. 
    * @param nv the value to test 
    */ 
    protected void updateEditable(String nv) { 
     if ("Other".equals(nv)) { 
      cb.setEditable(true); 
      FakeFocusTextField textField = (FakeFocusTextField) cb.getEditor(); 
      textField.requestFocus(); 
      textField.setFakeFocus(true); 
     } 
    } 

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

     Button b = new Button("GOOWE"); 

     Label choice = new Label("What type of Vehicle do you drive"); 
     cb.getItems().addAll("Car","Jeep","Bus","Other"); 

     cb.setPromptText("Select your Vehicle"); 

     cb.valueProperty().addListener((src, ov, nv) -> { 
      // fx8 bug: internals blow up when changing editable while showing 
      if (cb.isShowing() || cb.isEditable()) return; 
      updateEditable(nv); 
     }); 

     // hack around fx8 bug: 
     cb.setOnHidden(e -> { 
      if (cb.isEditable()) return; 
      updateEditable(cb.getValue()); 

     }); 

     // to see that editable is switched and textField focused 
     // when changing the value programmatically 
     b.setOnAction(e -> { 
      cb.setValue("Other"); 
     }); 

     VBox layout = new VBox(10); 
     layout.setPadding(new Insets(10,10,10,10)); 
     layout.getChildren().addAll(choice,cb,b); 
     Scene sc = new Scene(layout,200,400); 
     stage.setScene(sc); 
     stage.setTitle(FXUtils.version()); 
     stage.show(); 

    } 

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

來源

2017-10-18 12:35:17 kleopatra

的主要錯誤是隻更改組合框爲可編輯的同時價值被設置active.Thanks這麼多@kleopatra。 –

在JavaFx中，我向ComboBox對象添加操作後，如何使我的ComboBox可編輯

回答

相關問題