JavaFX - 为什么会抛出 java.lang.NullPointerException？
JavaFX - Why does this throw a java.lang.NullPointerException?
我有一个载入 MainView.fxml 的舞台。此 MainView.fxml 包括其他三个视图。在这些其他视图之一中，我有一些按钮，我可以毫无问题地对其进行完全修改。
这是我的 MainView.fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.layout.*?>
<BorderPane minHeight="-Infinity" minWidth="-Infinity" prefHeight="600.0" prefWidth="1000.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="controller.MainController">
<left>
<Pane prefHeight="800.0" prefWidth="300.0" BorderPane.alignment="CENTER">
<children>
<fx:include fx:id="ControlsView" source="ControlsView.fxml" />
<fx:include fx:id="ParametersView" source="ParametersView.fxml" />
</children>
</Pane>
</left>
<center>
<fx:include fx:id="CashRegisterView" source="CashRegisterView.fxml" />
</center>
</BorderPane>
例如，在 ControlsController 的控制器中，我有一个修改按钮的方法，效果很好：
@FXML
private void btStartActionEventHandler(MouseEvent event){
if(controlsModel.getBtStartValue() == ControlsModel.buttonStates.Start){
StartSuperSim();
controlsModel.setBtStartValue(ControlsModel.buttonStates.Pause);
btStart.setText(controlsModel.getBtStartValue().toString());
btStop.setDisable(false);
}
}
你可以清楚地看到我修改了 btStart 和 btStop 的属性。
但是当我尝试修改来自 ParametersView.fxml 的任何内容时，它会抛出 java.lang.reflect.InvocationTargetException、java.lang.reflect.InvocationTargetException 和 java.lang.NullPointerException。如完整 stackTrace 中所示 here。
这里是有问题的代码片段：
public class CashRegisterController extends BaseController{
@FXML
private Pane pCashRegister;
@FXML
public void CreateCashRegisters(){
Pane pane = new Pane();
pane.setStyle("-fx-background-color: black;");
this.pCashRegister.getChildren().add(0, pane);
}
}
我没有创建 pCashRegister 的实例，因为我也没有在我的 ControlsController 中这样做。但是当我这样做时，它工作正常但它不会将 pane 添加到我的视图中。
@FXML
private Button btStart;
@FXML
private Button btStop;
最后我的 CashRegisterView.fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.layout.Pane?>
<Pane fx:id="pCashRegister" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="600.0" prefWidth="700.0" xmlns="http://javafx.com/javafx/8.0.102" xmlns:fx="http://javafx.com/fxml/1" fx:controller="controller.CashRegisterController">
有人可以解释一下这是如何工作的以及这里发生了什么吗？我就是想不通。我只是认为无论出于何种原因 CashRegisterView.fxml 都不会 link 我的 CashRegisterController 即使我指定了 fx:controller="controller.CashRegisterController".
编辑：
StartSuperSim()方法：
private void StartSuperSim(){
getCashRegisterController().CreateCashRegisters();
seconds = 0;
setSuperSim(new Timeline(new KeyFrame(Duration.seconds((1 / controlsModel.getAcceleration())), new EventHandler<ActionEvent>() {
@Override
public void handle(ActionEvent event) {
seconds++;
//System.out.println(seconds);
if((seconds % (int)controlsModel.getParametersModel().getTimeBetweenCustomers()) == 0){
//System.out.println("Fired");
}
}
})));
getSuperSim().setCycleCount(Timeline.INDEFINITE);
getSuperSim().play();
}
还有我的MainController.java：
package controller;
public class MainController extends BaseController{
private ControlsController controlsController;
private ParametersController parametersController;
private CashRegisterController cashRegisterController;
public MainController() {
controlsController = Controller.getInstance().getControlsController();
parametersController = Controller.getInstance().getParametersController();
cashRegisterController = Controller.getInstance().getCashRegisterController();
}
}
还有我用来传递实例的 Controller.java class：
package controller;
public class Controller {
private final static Controller instance = new Controller();
public static Controller getInstance() {
return instance;
}
private ControlsController controlsController = new ControlsController();
private ParametersController parametersController = new ParametersController();
private CashRegisterController cashRegisterController = new CashRegisterController();
public ControlsController getControlsController() {
return controlsController;
}
public ParametersController getParametersController() {
return parametersController;
}
public CashRegisterController getCashRegisterController() {
return cashRegisterController;
}
}
最后是完整的堆栈跟踪：
"D:\Program Files\Java\jdk1.8.0_102\bin\java" -Didea.launcher.port=7534 "-Didea.launcher.bin.path=D:\Program Files (x86)\JetBrains\IntelliJ IDEA 2016.2.5\bin" -Dfile.encoding=UTF-8 -classpath "D:\Program Files\Java\jdk1.8.0_102\jre\lib\charsets.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\deploy.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\access-bridge-64.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\cldrdata.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\dnsns.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\jaccess.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\jfxrt.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\localedata.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\nashorn.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\sunec.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\sunjce_provider.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\sunmscapi.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\sunpkcs11.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\zipfs.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\javaws.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\jce.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\jfr.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\jfxswt.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\jsse.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\management-agent.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\plugin.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\resources.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\rt.jar;D:\This PC\Documents\Projects\Java\SuperSim\out\production\SuperSim;D:\Program Files (x86)\JetBrains\IntelliJ IDEA 2016.2.5\lib\idea_rt.jar" com.intellij.rt.execution.application.AppMain Main
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1774)
at javafx.fxml.FXMLLoader$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.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$ClickGenerator.postProcess(Scene.java:3470)
at javafx.scene.Scene$ClickGenerator.access00(Scene.java:3398)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3766)
at javafx.scene.Scene$MouseHandler.access00(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:380)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:294)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent4(GlassViewEventHandler.java:416)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:415)
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$null8(WinApplication.java:191)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
... 31 more
Caused by: java.lang.NullPointerException
at controller.CashRegisterController.CreateCashRegisters(CashRegisterController.java:26)
at controller.ControlsController.StartSuperSim(ControlsController.java:95)
at controller.ControlsController.btStartActionEventHandler(ControlsController.java:69)
... 41 more
您在 Controller 单例中创建和存储的 CashRegisterController 实例与 FXMLLoader 在加载 CashRegisterView.fxml 时创建的实例不同。当然，FXMLLoader 在它创建的实例上初始化 @FXML 注释字段（它无法访问存储在单例中的实例，除非你有一个非常复杂的控制器工厂你没有'未显示）。
您应该使用嵌套控制器技术 shown in the documentation 来访问包含的 FXML 文件的控制器。简而言之，在您的 MainController 中，您可以：
package controller;
public class MainController extends BaseController{
// field names are formed by appending "Controller" to the fx:id attribute value:
@FXML
private ControlsController ControlsViewController;
@FXML
private ParametersController ParametersViewController;
@FXML
private CashRegisterController CashRegisterViewController;
// Remove this constructor:
// public MainController() {
//controlsController = Controller.getInstance().getControlsController();
//parametersController = Controller.getInstance().getParametersController();
//cashRegisterController = Controller.getInstance().getCashRegisterController();
// }
public void initialize() {
// give ControlsViewController access to CashRegisterViewController:
ControlsViewController.setCashRegisterViewController(CashRegisterViewController);
}
}
然后在ControlsController中定义明显的注入方法：
public class ControlsController {
private CashRegisterController cashRegisterController ;
public void setCashRegisterViewController(CashRegisterController cashRegisterController) {
this.cashRegisterController = cashRegisterController ;
}
// existing code...
private void StartSuperSim(){
// getCashRegisterController().CreateCashRegisters();
cashRegisterController.CreateCashRegisters();
seconds = 0;
setSuperSim(new Timeline(new KeyFrame(Duration.seconds((1 / controlsModel.getAcceleration())), new EventHandler<ActionEvent>() {
@Override
public void handle(ActionEvent event) {
seconds++;
//System.out.println(seconds);
if((seconds % (int)controlsModel.getParametersModel().getTimeBetweenCustomers()) == 0){
//System.out.println("Fired");
}
}
})));
getSuperSim().setCycleCount(Timeline.INDEFINITE);
getSuperSim().play();
}
// ...
}
您定义的 Controller 单例 class 不会做任何有用的事情，因为它存储的控制器实例不是连接到相应 FXML 文件的控制器实例。因此，这些控制器实例不能做任何影响显示的 UI 的事情（例如，将初始化其 @FXML 注释字段的 none）。您应该删除 class 和所有对它的引用。
其他一些注意事项：首先，控制器以您在此处尝试执行的方式和我展示的方式相互访问并不是很好的做法。使用 MVC/MVP 类型设计可能更好（您有视图和控制器，但任何地方都没有模型）。然后所有的控制器只共享一个模型实例，并访问和观察其中的相同数据。看看 的一个简单例子。
最后请用proper naming conventions。它使其他人更容易阅读和理解您的代码，syntax-highlighting 软件（例如本网站使用的软件）将更好地解析您的代码并正确突出显示它。
我有一个载入 MainView.fxml 的舞台。此 MainView.fxml 包括其他三个视图。在这些其他视图之一中，我有一些按钮，我可以毫无问题地对其进行完全修改。
这是我的 MainView.fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.layout.*?>
<BorderPane minHeight="-Infinity" minWidth="-Infinity" prefHeight="600.0" prefWidth="1000.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="controller.MainController">
<left>
<Pane prefHeight="800.0" prefWidth="300.0" BorderPane.alignment="CENTER">
<children>
<fx:include fx:id="ControlsView" source="ControlsView.fxml" />
<fx:include fx:id="ParametersView" source="ParametersView.fxml" />
</children>
</Pane>
</left>
<center>
<fx:include fx:id="CashRegisterView" source="CashRegisterView.fxml" />
</center>
</BorderPane>
例如，在 ControlsController 的控制器中，我有一个修改按钮的方法，效果很好：
@FXML
private void btStartActionEventHandler(MouseEvent event){
if(controlsModel.getBtStartValue() == ControlsModel.buttonStates.Start){
StartSuperSim();
controlsModel.setBtStartValue(ControlsModel.buttonStates.Pause);
btStart.setText(controlsModel.getBtStartValue().toString());
btStop.setDisable(false);
}
}
你可以清楚地看到我修改了 btStart 和 btStop 的属性。
但是当我尝试修改来自 ParametersView.fxml 的任何内容时，它会抛出 java.lang.reflect.InvocationTargetException、java.lang.reflect.InvocationTargetException 和 java.lang.NullPointerException。如完整 stackTrace 中所示 here。
这里是有问题的代码片段：
public class CashRegisterController extends BaseController{
@FXML
private Pane pCashRegister;
@FXML
public void CreateCashRegisters(){
Pane pane = new Pane();
pane.setStyle("-fx-background-color: black;");
this.pCashRegister.getChildren().add(0, pane);
}
}
我没有创建 pCashRegister 的实例，因为我也没有在我的 ControlsController 中这样做。但是当我这样做时，它工作正常但它不会将 pane 添加到我的视图中。
@FXML
private Button btStart;
@FXML
private Button btStop;
最后我的 CashRegisterView.fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.layout.Pane?>
<Pane fx:id="pCashRegister" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="600.0" prefWidth="700.0" xmlns="http://javafx.com/javafx/8.0.102" xmlns:fx="http://javafx.com/fxml/1" fx:controller="controller.CashRegisterController">
有人可以解释一下这是如何工作的以及这里发生了什么吗？我就是想不通。我只是认为无论出于何种原因 CashRegisterView.fxml 都不会 link 我的 CashRegisterController 即使我指定了 fx:controller="controller.CashRegisterController".
编辑：
StartSuperSim()方法：
private void StartSuperSim(){
getCashRegisterController().CreateCashRegisters();
seconds = 0;
setSuperSim(new Timeline(new KeyFrame(Duration.seconds((1 / controlsModel.getAcceleration())), new EventHandler<ActionEvent>() {
@Override
public void handle(ActionEvent event) {
seconds++;
//System.out.println(seconds);
if((seconds % (int)controlsModel.getParametersModel().getTimeBetweenCustomers()) == 0){
//System.out.println("Fired");
}
}
})));
getSuperSim().setCycleCount(Timeline.INDEFINITE);
getSuperSim().play();
}
还有我的MainController.java：
package controller;
public class MainController extends BaseController{
private ControlsController controlsController;
private ParametersController parametersController;
private CashRegisterController cashRegisterController;
public MainController() {
controlsController = Controller.getInstance().getControlsController();
parametersController = Controller.getInstance().getParametersController();
cashRegisterController = Controller.getInstance().getCashRegisterController();
}
}
还有我用来传递实例的 Controller.java class：
package controller;
public class Controller {
private final static Controller instance = new Controller();
public static Controller getInstance() {
return instance;
}
private ControlsController controlsController = new ControlsController();
private ParametersController parametersController = new ParametersController();
private CashRegisterController cashRegisterController = new CashRegisterController();
public ControlsController getControlsController() {
return controlsController;
}
public ParametersController getParametersController() {
return parametersController;
}
public CashRegisterController getCashRegisterController() {
return cashRegisterController;
}
}
最后是完整的堆栈跟踪：
"D:\Program Files\Java\jdk1.8.0_102\bin\java" -Didea.launcher.port=7534 "-Didea.launcher.bin.path=D:\Program Files (x86)\JetBrains\IntelliJ IDEA 2016.2.5\bin" -Dfile.encoding=UTF-8 -classpath "D:\Program Files\Java\jdk1.8.0_102\jre\lib\charsets.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\deploy.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\access-bridge-64.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\cldrdata.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\dnsns.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\jaccess.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\jfxrt.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\localedata.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\nashorn.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\sunec.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\sunjce_provider.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\sunmscapi.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\sunpkcs11.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\ext\zipfs.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\javaws.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\jce.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\jfr.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\jfxswt.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\jsse.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\management-agent.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\plugin.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\resources.jar;D:\Program Files\Java\jdk1.8.0_102\jre\lib\rt.jar;D:\This PC\Documents\Projects\Java\SuperSim\out\production\SuperSim;D:\Program Files (x86)\JetBrains\IntelliJ IDEA 2016.2.5\lib\idea_rt.jar" com.intellij.rt.execution.application.AppMain Main
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1774)
at javafx.fxml.FXMLLoader$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.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$ClickGenerator.postProcess(Scene.java:3470)
at javafx.scene.Scene$ClickGenerator.access00(Scene.java:3398)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3766)
at javafx.scene.Scene$MouseHandler.access00(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:380)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:294)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent4(GlassViewEventHandler.java:416)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:415)
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$null8(WinApplication.java:191)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
... 31 more
Caused by: java.lang.NullPointerException
at controller.CashRegisterController.CreateCashRegisters(CashRegisterController.java:26)
at controller.ControlsController.StartSuperSim(ControlsController.java:95)
at controller.ControlsController.btStartActionEventHandler(ControlsController.java:69)
... 41 more
您在 Controller 单例中创建和存储的 CashRegisterController 实例与 FXMLLoader 在加载 CashRegisterView.fxml 时创建的实例不同。当然，FXMLLoader 在它创建的实例上初始化 @FXML 注释字段（它无法访问存储在单例中的实例，除非你有一个非常复杂的控制器工厂你没有'未显示）。
您应该使用嵌套控制器技术 shown in the documentation 来访问包含的 FXML 文件的控制器。简而言之，在您的 MainController 中，您可以：
package controller;
public class MainController extends BaseController{
// field names are formed by appending "Controller" to the fx:id attribute value:
@FXML
private ControlsController ControlsViewController;
@FXML
private ParametersController ParametersViewController;
@FXML
private CashRegisterController CashRegisterViewController;
// Remove this constructor:
// public MainController() {
//controlsController = Controller.getInstance().getControlsController();
//parametersController = Controller.getInstance().getParametersController();
//cashRegisterController = Controller.getInstance().getCashRegisterController();
// }
public void initialize() {
// give ControlsViewController access to CashRegisterViewController:
ControlsViewController.setCashRegisterViewController(CashRegisterViewController);
}
}
然后在ControlsController中定义明显的注入方法：
public class ControlsController {
private CashRegisterController cashRegisterController ;
public void setCashRegisterViewController(CashRegisterController cashRegisterController) {
this.cashRegisterController = cashRegisterController ;
}
// existing code...
private void StartSuperSim(){
// getCashRegisterController().CreateCashRegisters();
cashRegisterController.CreateCashRegisters();
seconds = 0;
setSuperSim(new Timeline(new KeyFrame(Duration.seconds((1 / controlsModel.getAcceleration())), new EventHandler<ActionEvent>() {
@Override
public void handle(ActionEvent event) {
seconds++;
//System.out.println(seconds);
if((seconds % (int)controlsModel.getParametersModel().getTimeBetweenCustomers()) == 0){
//System.out.println("Fired");
}
}
})));
getSuperSim().setCycleCount(Timeline.INDEFINITE);
getSuperSim().play();
}
// ...
}
您定义的 Controller 单例 class 不会做任何有用的事情，因为它存储的控制器实例不是连接到相应 FXML 文件的控制器实例。因此，这些控制器实例不能做任何影响显示的 UI 的事情（例如，将初始化其 @FXML 注释字段的 none）。您应该删除 class 和所有对它的引用。
其他一些注意事项：首先，控制器以您在此处尝试执行的方式和我展示的方式相互访问并不是很好的做法。使用 MVC/MVP 类型设计可能更好（您有视图和控制器，但任何地方都没有模型）。然后所有的控制器只共享一个模型实例，并访问和观察其中的相同数据。看看
最后请用proper naming conventions。它使其他人更容易阅读和理解您的代码，syntax-highlighting 软件（例如本网站使用的软件）将更好地解析您的代码并正确突出显示它。