JavaFX web部署: FXMLLoader NullPointerException

Question

我想尝试JavaFX web浏览器部署，因此我使用IntelliJ社区版14.0.2 JavaFX应用程序模板启动了一个非常简单的测试项目。下面是代码：(没有插件、外部库或maven)

Main.java

@Override
public void start(Stage primaryStage) throws Exception{
    Parent root = FXMLLoader.load(getClass().getResource("sample.fxml"));
    primaryStage.setTitle("Hello World");
    primaryStage.setScene(new Scene(root, 300, 275));
    primaryStage.show();
}


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

Controller.java (附在sample.fxml上)

@FXML
private TextField textField;

@FXML
private Label label;

@FXML
private void setLabelText() {
    label.setText(textField.getText());
}

sample.fxml (布局文件)

<VBox alignment="TOP_CENTER" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity"
      prefHeight="400.0" prefWidth="600.0" spacing="20.0" xmlns="http://javafx.com/javafx/8"
      xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller">
   <padding>
      <Insets bottom="20.0" left="20.0" right="20.0" top="20.0"/>
   </padding>
   <TextField fx:id="textField" onAction="#setLabelText"/>
   <Label fx:id="label" text="Label">
      <font>
         <Font size="96.0"/>
      </font>
   </Label>
</VBox>

现在，当我将应用程序构建为JAR时，它没有任何问题地运行。但是，当我使用预定义的"JavaFXApp“工件构建它时，它会生成一个html、一个jnlp和一个jar。当我在我的web浏览器(Firefox Nightle64bit)中打开html时，它会给出以下错误：

java.lang.NullPointerException: Location is required.
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml.FXMLLoader.load(Unknown Source)
    at sample.Main.start(Main.java:13)
    at com.sun.javafx.applet.FXApplet2$2.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$null$164(Unknown Source)
    at com.sun.javafx.application.PlatformImpl$$Lambda$45/1838209255.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$165(Unknown Source)
    at com.sun.javafx.application.PlatformImpl$$Lambda$44/1604839423.run(Unknown Source)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(Unknown Source)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$141(Unknown Source)
    at com.sun.glass.ui.win.WinApplication$$Lambda$36/982109627.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.NullPointerException: Location is required.
    at com.sun.javafx.applet.FXApplet2$2.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$null$164(Unknown Source)
    at com.sun.javafx.application.PlatformImpl$$Lambda$45/1838209255.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$165(Unknown Source)
    at com.sun.javafx.application.PlatformImpl$$Lambda$44/1604839423.run(Unknown Source)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(Unknown Source)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$141(Unknown Source)
    at com.sun.glass.ui.win.WinApplication$$Lambda$36/982109627.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NullPointerException: Location is required.
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml.FXMLLoader.load(Unknown Source)
    at sample.Main.start(Main.java:13)
    ... 11 more

相关代码行似乎是

Parent root = FXMLLoader.load(getClass().getResource("sample.fxml"));

然而，这一行代码在构建并作为单个独立JAR打开时工作得很好！知道错误发生的原因或如何修复吗？

Answer 1

这个错误有点神秘，但可以理解。您正在获得一个带有本地化消息"Location“的空指针，表明您没有设置查找FXML的位置。

getClass().getResource("sample.fxml")返回null，因此FXMLLoader抛出一个空指针。检查fxml的路径，您可能希望在它前面加上一个'/'，比如"/sample.fxml“。