使用 Scene Builder 8.0 在 JavaFX 中使用 setCenter() 方法获取空指针异常
Getting Null Pointer Exception with setCenter() method in JavaFX with Scene Builder 8.0
我创建了一个小程序来重现我在实际项目中遇到的错误。我有一个名为 MainWindow.java 的控制器 class，它负责两个 .fxml 文件：MainWindow.fxml 和 AnchorTest.fxml.
控制器代码 class:
package projecterror.controller;
import java.io.IOException;
import javafx.application.Application;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.geometry.Rectangle2D;
import javafx.scene.Scene;
import javafx.scene.control.Menu;
import javafx.scene.control.MenuItem;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;
import javafx.stage.Screen;
import javafx.stage.Stage;
public class MainWindow extends Application {
private Stage primaryStage;
private BorderPane mainWindow;
@FXML
Menu menuFile, menuAnalysis;
@FXML
MenuItem menuNew;
@FXML
private void initialize() {
menuNew.setOnAction((event) -> {
try {
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("../view/AnchorTest.fxml"));
AnchorPane anchorTest = (AnchorPane) loader.load();
mainWindow.setCenter(anchorTest);
} catch (IOException e) {
e.printStackTrace();
}
});
}
@Override
public void start(Stage primaryStage) throws Exception {
this.primaryStage = primaryStage;
this.primaryStage.setTitle("Test Project");
initMainWindow();
}
public void initMainWindow() {
try {
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("../view/MainWindow.fxml"));
mainWindow = (BorderPane) loader.load();
Scene scene = new Scene(mainWindow);
primaryStage.setScene(scene);
//Fullscreen
Screen screen = Screen.getPrimary();
Rectangle2D bounds = screen.getVisualBounds();
primaryStage.setX(bounds.getMinX());
primaryStage.setY(bounds.getMinY());
primaryStage.setWidth(bounds.getWidth());
primaryStage.setHeight(bounds.getHeight());
primaryStage.setResizable(false);
primaryStage.show();
} catch (IOException e) {
e.printStackTrace();
}
}
}
MainWindow.fxml 是一个 BorderPane，它在 top 上有一个 MenuBar。
代码：
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Menu?>
<?import javafx.scene.control.MenuBar?>
<?import javafx.scene.control.MenuItem?>
<?import javafx.scene.control.SeparatorMenuItem?>
<?import javafx.scene.layout.BorderPane?>
<BorderPane style="-fx-background-color: #DCDCDC;" xmlns="http://javafx.com/javafx/9.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="projecterror.controller.MainWindow">
<top>
<MenuBar BorderPane.alignment="CENTER">
<menus>
<Menu fx:id="menuFile" mnemonicParsing="false" text="File">
<items>
<Menu fx:id="menuAnalysis" mnemonicParsing="false" text="Analysis">
<items>
<MenuItem fx:id="menuNew" mnemonicParsing="false" text="New" />
</items>
</Menu>
</items>
</Menu>
</menus>
</MenuBar>
</top>
</BorderPane>
AnchorTest.fxml 是一个 AnchorPane，它有两个 AnchorPane。
代码：
<?xml version="1.0" encoding="UTF-8"?>
<?import java.lang.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane xmlns:fx="http://javafx.com/fxml/1">
<children>
<AnchorPane layoutX="6.0" layoutY="450.0" />
<AnchorPane layoutX="6.0" layoutY="569.0" prefHeight="116.0" prefWidth="730.0">
<Button layoutX="6.0" layoutY="26.0" mnemonicParsing="false" prefHeight="25.0" prefWidth="102.0" text="Button 1" />
<Button layoutX="115.0" layoutY="26.0" mnemonicParsing="false" prefWidth="102.0" text="Button 2" />
<Button layoutX="226.0" layoutY="26.0" mnemonicParsing="false" prefWidth="102.0" text="Button 3" />
<Button layoutX="115.0" layoutY="75.0" mnemonicParsing="false" prefWidth="102.0" text="Button 4" />
<Button layoutX="383.0" layoutY="26.0" mnemonicParsing="false" prefWidth="102.0" text="Button 5" />
<Button layoutX="491.0" layoutY="26.0" mnemonicParsing="false" prefWidth="102.0" text="Button 6" />
<Button layoutX="600.0" layoutY="26.0" mnemonicParsing="false" prefWidth="102.0" text="Button 7" />
<Button layoutX="491.0" layoutY="75.0" mnemonicParsing="false" prefWidth="102.0" text="Button 8" />
<Button layoutX="600.0" layoutY="75.0" mnemonicParsing="false" prefWidth="102.0" text="Button 9" />
<TextField alignment="TOP_CENTER" layoutX="341.0" layoutY="26.0" prefHeight="25.0" prefWidth="28.0" text="10" />
</AnchorPane>
</children>
</AnchorPane>
在 MainWindow.fxml 上，单击菜单 File > Analysis > New 后，它应该将 AnchorTest.fxml 内容置于 MainWindow.fxml 中心。但是，我收到以下堆栈跟踪错误：
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at projecterror.controller.MainWindow.lambda[=13=](MainWindow.java:35)
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.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
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.control.MenuItem.fire(MenuItem.java:462)
at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.doSelect(ContextMenuContent.java:1405)
at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.lambda$createChildren3(ContextMenuContent.java:1358)
at com.sun.javafx.event.CompositeEventHandler$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.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)
标记 NPE 的行是：
mainWindow.setCenter(anchorTest);
我读过其他类似的问题，但大多数问题都与 fxml 文件的路径有关。我坚信这不是问题，因为在我的实际项目中，我对其他视图使用相同的 type 路径，到目前为止我没有遇到问题。
我已经上传了项目 here 以防有人想要 运行 该程序。
项目结构如下：
提前致谢，如有任何帮助，我们将不胜感激！
当您启动一个 JavaFX 应用程序时，您的应用程序实例 class 被创建，并且（在发生的其他事情中）， start() 方法被调用 Application FX 应用程序线程上的实例。
加载 FXML 文件时，如果 FXML 文件指定了一个控制器 class，则会创建该控制器的一个实例 class，@FXML-注释字段将被注入该实例，并调用 initialize() 方法。所有这一切都发生在调用 FXMLLoader.load().
期间
因此，在您的代码中，您最终得到 MainWindow 的两个不同实例。 start() 方法在一个实例上调用，它初始化 mainWindow 字段，initialize() 方法在另一个实例上调用。由于 mainWindow 从未在第二个实例中初始化，因此当您尝试在 initialize() 方法中取消引用它时会出现空指针异常。
将控制器 class 与 Application class 分开。 Application class 除了管理整个应用程序的生命周期外什么都不做（通常，它应该实现启动应用程序所需的代码）：
package projecterror.controller;
import java.io.IOException;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.geometry.Rectangle2D;
import javafx.scene.Scene;
import javafx.scene.layout.BorderPane;
import javafx.stage.Screen;
import javafx.stage.Stage;
public class MainWindow extends Application {
@Override
public void start(Stage primaryStage) throws Exception {
primaryStage.setTitle("Test Project");
initMainWindow(primaryStage);
}
public void initMainWindow(Stage primaryStage) {
try {
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("../view/MainWindow.fxml"));
BorderPane mainWindow = loader.load();
Scene scene = new Scene(mainWindow);
primaryStage.setScene(scene);
//Fullscreen
Screen screen = Screen.getPrimary();
Rectangle2D bounds = screen.getVisualBounds();
primaryStage.setX(bounds.getMinX());
primaryStage.setY(bounds.getMinY());
primaryStage.setWidth(bounds.getWidth());
primaryStage.setHeight(bounds.getHeight());
primaryStage.setResizable(false);
primaryStage.show();
} catch (IOException e) {
e.printStackTrace();
}
}
}
package projecterror.controller;
import java.io.IOException;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.control.Menu;
import javafx.scene.control.MenuItem;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;
public class MainWindowController {
@FXML
private BorderPane mainWindow;
@FXML
Menu menuFile, menuAnalysis;
@FXML
MenuItem menuNew;
@FXML
private void initialize() {
menuNew.setOnAction((event) -> {
try {
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("../view/AnchorTest.fxml"));
AnchorPane anchorTest = (AnchorPane) loader.load();
mainWindow.setCenter(anchorTest);
} catch (IOException e) {
e.printStackTrace();
}
});
}
}
为了让控制器访问 BorderPane，您需要从 FXML 中注入它（注意上面控制器代码中的注解）。在 FXML 文件中的元素中添加一个 fx:id：
<BorderPane style="-fx-background-color: #DCDCDC;" fx:id="mainWindow"
xmlns="http://javafx.com/javafx/9.0.1" xmlns:fx="http://javafx.com/fxml/1"
fx:controller="projecterror.controller.MainWindowController">
我创建了一个小程序来重现我在实际项目中遇到的错误。我有一个名为 MainWindow.java 的控制器 class，它负责两个 .fxml 文件：MainWindow.fxml 和 AnchorTest.fxml.
控制器代码 class:
package projecterror.controller;
import java.io.IOException;
import javafx.application.Application;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.geometry.Rectangle2D;
import javafx.scene.Scene;
import javafx.scene.control.Menu;
import javafx.scene.control.MenuItem;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;
import javafx.stage.Screen;
import javafx.stage.Stage;
public class MainWindow extends Application {
private Stage primaryStage;
private BorderPane mainWindow;
@FXML
Menu menuFile, menuAnalysis;
@FXML
MenuItem menuNew;
@FXML
private void initialize() {
menuNew.setOnAction((event) -> {
try {
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("../view/AnchorTest.fxml"));
AnchorPane anchorTest = (AnchorPane) loader.load();
mainWindow.setCenter(anchorTest);
} catch (IOException e) {
e.printStackTrace();
}
});
}
@Override
public void start(Stage primaryStage) throws Exception {
this.primaryStage = primaryStage;
this.primaryStage.setTitle("Test Project");
initMainWindow();
}
public void initMainWindow() {
try {
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("../view/MainWindow.fxml"));
mainWindow = (BorderPane) loader.load();
Scene scene = new Scene(mainWindow);
primaryStage.setScene(scene);
//Fullscreen
Screen screen = Screen.getPrimary();
Rectangle2D bounds = screen.getVisualBounds();
primaryStage.setX(bounds.getMinX());
primaryStage.setY(bounds.getMinY());
primaryStage.setWidth(bounds.getWidth());
primaryStage.setHeight(bounds.getHeight());
primaryStage.setResizable(false);
primaryStage.show();
} catch (IOException e) {
e.printStackTrace();
}
}
}
MainWindow.fxml 是一个 BorderPane，它在 top 上有一个 MenuBar。
代码：
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Menu?>
<?import javafx.scene.control.MenuBar?>
<?import javafx.scene.control.MenuItem?>
<?import javafx.scene.control.SeparatorMenuItem?>
<?import javafx.scene.layout.BorderPane?>
<BorderPane style="-fx-background-color: #DCDCDC;" xmlns="http://javafx.com/javafx/9.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="projecterror.controller.MainWindow">
<top>
<MenuBar BorderPane.alignment="CENTER">
<menus>
<Menu fx:id="menuFile" mnemonicParsing="false" text="File">
<items>
<Menu fx:id="menuAnalysis" mnemonicParsing="false" text="Analysis">
<items>
<MenuItem fx:id="menuNew" mnemonicParsing="false" text="New" />
</items>
</Menu>
</items>
</Menu>
</menus>
</MenuBar>
</top>
</BorderPane>
AnchorTest.fxml 是一个 AnchorPane，它有两个 AnchorPane。
代码：
<?xml version="1.0" encoding="UTF-8"?>
<?import java.lang.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane xmlns:fx="http://javafx.com/fxml/1">
<children>
<AnchorPane layoutX="6.0" layoutY="450.0" />
<AnchorPane layoutX="6.0" layoutY="569.0" prefHeight="116.0" prefWidth="730.0">
<Button layoutX="6.0" layoutY="26.0" mnemonicParsing="false" prefHeight="25.0" prefWidth="102.0" text="Button 1" />
<Button layoutX="115.0" layoutY="26.0" mnemonicParsing="false" prefWidth="102.0" text="Button 2" />
<Button layoutX="226.0" layoutY="26.0" mnemonicParsing="false" prefWidth="102.0" text="Button 3" />
<Button layoutX="115.0" layoutY="75.0" mnemonicParsing="false" prefWidth="102.0" text="Button 4" />
<Button layoutX="383.0" layoutY="26.0" mnemonicParsing="false" prefWidth="102.0" text="Button 5" />
<Button layoutX="491.0" layoutY="26.0" mnemonicParsing="false" prefWidth="102.0" text="Button 6" />
<Button layoutX="600.0" layoutY="26.0" mnemonicParsing="false" prefWidth="102.0" text="Button 7" />
<Button layoutX="491.0" layoutY="75.0" mnemonicParsing="false" prefWidth="102.0" text="Button 8" />
<Button layoutX="600.0" layoutY="75.0" mnemonicParsing="false" prefWidth="102.0" text="Button 9" />
<TextField alignment="TOP_CENTER" layoutX="341.0" layoutY="26.0" prefHeight="25.0" prefWidth="28.0" text="10" />
</AnchorPane>
</children>
</AnchorPane>
在 MainWindow.fxml 上，单击菜单 File > Analysis > New 后，它应该将 AnchorTest.fxml 内容置于 MainWindow.fxml 中心。但是，我收到以下堆栈跟踪错误：
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at projecterror.controller.MainWindow.lambda[=13=](MainWindow.java:35)
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.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
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.control.MenuItem.fire(MenuItem.java:462)
at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.doSelect(ContextMenuContent.java:1405)
at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.lambda$createChildren3(ContextMenuContent.java:1358)
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$MouseHandler.access00(Scene.java:3485)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
at javafx.scene.Scene$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)
标记 NPE 的行是：
mainWindow.setCenter(anchorTest);
我读过其他类似的问题，但大多数问题都与 fxml 文件的路径有关。我坚信这不是问题，因为在我的实际项目中，我对其他视图使用相同的 type 路径，到目前为止我没有遇到问题。
我已经上传了项目 here 以防有人想要 运行 该程序。
项目结构如下：
提前致谢，如有任何帮助，我们将不胜感激！
当您启动一个 JavaFX 应用程序时，您的应用程序实例 class 被创建，并且（在发生的其他事情中）， start() 方法被调用 Application FX 应用程序线程上的实例。
加载 FXML 文件时，如果 FXML 文件指定了一个控制器 class，则会创建该控制器的一个实例 class，@FXML-注释字段将被注入该实例，并调用 initialize() 方法。所有这一切都发生在调用 FXMLLoader.load().
因此，在您的代码中，您最终得到 MainWindow 的两个不同实例。 start() 方法在一个实例上调用，它初始化 mainWindow 字段，initialize() 方法在另一个实例上调用。由于 mainWindow 从未在第二个实例中初始化，因此当您尝试在 initialize() 方法中取消引用它时会出现空指针异常。
将控制器 class 与 Application class 分开。 Application class 除了管理整个应用程序的生命周期外什么都不做（通常，它应该实现启动应用程序所需的代码）：
package projecterror.controller;
import java.io.IOException;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.geometry.Rectangle2D;
import javafx.scene.Scene;
import javafx.scene.layout.BorderPane;
import javafx.stage.Screen;
import javafx.stage.Stage;
public class MainWindow extends Application {
@Override
public void start(Stage primaryStage) throws Exception {
primaryStage.setTitle("Test Project");
initMainWindow(primaryStage);
}
public void initMainWindow(Stage primaryStage) {
try {
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("../view/MainWindow.fxml"));
BorderPane mainWindow = loader.load();
Scene scene = new Scene(mainWindow);
primaryStage.setScene(scene);
//Fullscreen
Screen screen = Screen.getPrimary();
Rectangle2D bounds = screen.getVisualBounds();
primaryStage.setX(bounds.getMinX());
primaryStage.setY(bounds.getMinY());
primaryStage.setWidth(bounds.getWidth());
primaryStage.setHeight(bounds.getHeight());
primaryStage.setResizable(false);
primaryStage.show();
} catch (IOException e) {
e.printStackTrace();
}
}
}
package projecterror.controller;
import java.io.IOException;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.control.Menu;
import javafx.scene.control.MenuItem;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;
public class MainWindowController {
@FXML
private BorderPane mainWindow;
@FXML
Menu menuFile, menuAnalysis;
@FXML
MenuItem menuNew;
@FXML
private void initialize() {
menuNew.setOnAction((event) -> {
try {
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("../view/AnchorTest.fxml"));
AnchorPane anchorTest = (AnchorPane) loader.load();
mainWindow.setCenter(anchorTest);
} catch (IOException e) {
e.printStackTrace();
}
});
}
}
为了让控制器访问 BorderPane，您需要从 FXML 中注入它（注意上面控制器代码中的注解）。在 FXML 文件中的元素中添加一个 fx:id：
<BorderPane style="-fx-background-color: #DCDCDC;" fx:id="mainWindow"
xmlns="http://javafx.com/javafx/9.0.1" xmlns:fx="http://javafx.com/fxml/1"
fx:controller="projecterror.controller.MainWindowController">