javafx在string.equals（）中获取错误

在我的项目中，a遇到了一个问题

我在combobox中添加了一项：

@FXML
private ComboBox schedule;

我增加了价值

 schedule.getItems().add("Create a new Schedule"); 

现在我比较价值：

     String p= (String) schedule.getSelectionModel().getSelectedItem();

    System.out.println(p);
    if(p.equals("Create a new Schedule")){
     System.out.println("got it);
    }

我在网上出错了

     if(p.equals("Create a new Schedule")){

错误：

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1768)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1651)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
null
    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.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:204)
    at javafx.scene.Node.fireEvent(Node.java:8175)
    at javafx.scene.control.ComboBoxBase.valueInvalidated(ComboBoxBase.java:136)
    at javafx.scene.control.ComboBoxBase$2.invalidated(ComboBoxBase.java:161)
    at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:111)
    at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:145)
    at javafx.scene.control.ComboBoxBase.setValue(ComboBoxBase.java:167)
    at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin.setTextFromTextFieldIntoComboBoxValue(ComboBoxListViewSkin.java:512)
    at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin.access$200(ComboBoxListViewSkin.java:57)
    at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin$6.changed(ComboBoxListViewSkin.java:416)
    at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin$6.changed(ComboBoxListViewSkin.java:406)
    at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:347)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
    at javafx.beans.property.ReadOnlyBooleanPropertyBase.fireValueChangedEvent(ReadOnlyBooleanPropertyBase.java:72)
    at javafx.scene.Node$FocusedProperty.notifyListeners(Node.java:7486)
    at javafx.scene.Node.setFocused(Node.java:7537)
    at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin$FakeFocusTextField.setFakeFocus(ComboBoxListViewSkin.java:697)
    at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin$2.changed(ComboBoxListViewSkin.java:145)
    at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin$2.changed(ComboBoxListViewSkin.java:141)
    at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:347)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
    at javafx.beans.property.ReadOnlyBooleanPropertyBase.fireValueChangedEvent(ReadOnlyBooleanPropertyBase.java:72)
    at javafx.scene.Node$FocusedProperty.notifyListeners(Node.java:7486)
    at javafx.scene.Node.setFocused(Node.java:7537)
    at javafx.scene.Scene$KeyHandler.setWindowFocused(Scene.java:3918)
    at javafx.scene.Scene$KeyHandler$1.invalidated(Scene.java:3937)
    at com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:135)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
    at javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl.fireValueChangedEvent(ReadOnlyBooleanWrapper.java:178)
    at javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl.access$100(ReadOnlyBooleanWrapper.java:148)
    at javafx.beans.property.ReadOnlyBooleanWrapper.fireValueChangedEvent(ReadOnlyBooleanWrapper.java:144)
    at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:110)
    at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:143)
    at javafx.stage.Window.setFocused(Window.java:409)
    at com.sun.javafx.stage.WindowPeerListener.changedFocused(WindowPeerListener.java:59)
    at com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:89)
    at com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:39)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassWindowEventHandler.handleWindowEvent(GlassWindowEventHandler.java:130)
    at com.sun.glass.ui.Window.handleWindowEvent(Window.java:1235)
    at com.sun.glass.ui.Window.notifyFocus(Window.java:1210)
    at com.sun.glass.ui.win.WinWindow._setVisible(Native Method)
    at com.sun.glass.ui.Window.setVisible(Window.java:570)
    at com.sun.javafx.tk.quantum.WindowStage.setVisible(WindowStage.java:455)
    at javafx.stage.Window$9.invalidated(Window.java:776)
    at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:109)
    at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:143)
    at javafx.stage.Window.setShowing(Window.java:826)
    at javafx.stage.Window.hide(Window.java:851)
    at javafx.stage.Stage.close(Stage.java:1176)
    at schoolmanagement2.DashboardController.close(DashboardController.java:213)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1763)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1651)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.event.Event.fireEvent(Event.java:204)
    at javafx.scene.Scene$ClickGenerator.postProcess(Scene.java:3456)
    at javafx.scene.Scene$ClickGenerator.access$8300(Scene.java:3387)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3755)
    at javafx.scene.Scene$MouseHandler.access$1800(Scene.java:3471)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1695)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2486)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:314)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:243)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:345)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:526)
    at com.sun.glass.ui.View.notifyMouse(View.java:898)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.access$300(WinApplication.java:39)
    at com.sun.glass.ui.win.WinApplication$4$1.run(WinApplication.java:112)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1763)
    ... 110 more
Caused by: java.lang.NullPointerException
    at schoolmanagement2.ScheduleController.schedule(ScheduleController.java:462)

---

帮帮我。无法找到我出现此错误的原因。

从

选择模型的文档中，porperty:

所选项目为空，表示没有选择，或[…]

您可以通过使用
p
切换sting常量来修复代码：

if("Create a new Schedule".equals(p)){

我已经更新了代码，请跟踪<代码>我在线上遇到错误

正常。。但是错误是什么？

p

为空（即未选择任何内容）。请阅读有关此主题的许多问题中的任何一个：例如，否我选择了一个项目如果

ScheduleController

中的第462行是您显示的行（

if（p.equals（…）{

），则

p

必须是

null

。根据说明，如果没有选择的项目，这仅是

null

。