java - 调用方法时出错 - 尝试部署 Javafx 应用程序时无法启动 JVM

Question

我使用 javafx 构建了一个简单的程序，并且已经开始部署应用程序以在 intelliJ(社区版)之外使用。我似乎无法弄清楚为什么当我尝试在 IDE 之外启动 exe 时该方法没有被调用。它显示两个警报框，第一个显示“调用方法时出错”，第二个显示“在我尝试打开 JVM 后无法启动 JVM”来自资源管理器的 exe。

    package sample;
    import javafx.application.Application;
    import javafx.event.ActionEvent;
    import javafx.event.EventHandler;
    import javafx.geometry.Insets;
    import javafx.geometry.Pos;
    import javafx.scene.Scene;
    import javafx.scene.control.Label;
    import javafx.scene.control.PasswordField;
    import javafx.scene.control.TextField;
    import javafx.scene.layout.GridPane;
    import javafx.scene.layout.HBox;
    import javafx.scene.layout.StackPane;
    import javafx.scene.control.Button;
    import javafx.scene.paint.Color;
    import javafx.scene.text.Font;
    import javafx.scene.text.FontWeight;
    import javafx.scene.text.Text;
    import javafx.stage.Stage;

    public class Main extends Application {
        public static void main(String[] args) {
            launch(args);
        }

        @Override
        public void start(Stage primaryStage) throws Exception{
            primaryStage.setTitle("Welcome");
            primaryStage.setResizable(false);


         primaryStage.show();
            GridPane grid = new GridPane();
            grid.setAlignment(Pos.CENTER);
            grid.setHgap(10);
            grid.setVgap(10);
            grid.setPadding(new Insets(25, 25, 25, 25));
            //Adding text labels and text fields
            Text sceneTitle = new Text("Welcome");
            sceneTitle.setId("welcome-text");
            grid.add(sceneTitle, 0, 0,2, 1);
            TextField userTextField = new TextField();
            grid.add(userTextField, 1,1);
            Label userName = new Label("User Name: ");
            grid.add(userName, 0 ,1);
            Label pw = new Label("Password: ");
            grid.add(pw, 0,2);
            PasswordField pwBox = new PasswordField();
            grid.add(pwBox,1,2);
            //grid lines for debugging
            grid.setGridLinesVisible(false);
            //grid lines for debugging
            Button btn = new Button("Sign In");
            HBox hbBtn = new HBox(10);
            hbBtn.setAlignment(Pos.BOTTOM_RIGHT);
            hbBtn.getChildren().add(btn);
            grid.add(hbBtn, 1,4);
            final Text actionTarget = new Text();
            grid.add(actionTarget,1,6);
            btn.setOnAction(e -> {actionTarget.setText("Sign In button 
Pressed");});
        actionTarget.setId("actiontarget");
        Scene scene = new Scene(grid, 300, 275);
        primaryStage.setScene(scene);
        //Initialize sytlesheets variable
        scene.getStylesheets().add(Main.class.getResource("Login.css").toExternalForm());
        primaryStage.show();
    }
}

这是我的 Controller 类(笑)

    package sample;

    public class Controller {
    }

最后......我的fxml

<?import javafx.geometry.Insets?>
<?import javafx.scene.layout.GridPane?>

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<GridPane fx:controller="sample.Controller"
          xmlns:fx="http://javafx.com/fxml" alignment="center" hgap="10" vgap="10">
</GridPane>

我要帮忙的最后一件事是这里，但我不知道如何阅读它以了解问题的根源......

C:\Users\Joop\IdeaProjects\Hello\out\artifacts\JavaFXApp\bundles>java -jar "JavaFXApp.jar"
Exception in Application start method
java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
        at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at sun.launcher.LauncherHelper$FXHelper.main(Unknown Source)
Caused by: java.lang.RuntimeException: Exception in Application start method
        at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
        at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$154(LauncherImpl.java:182)
        at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NullPointerException
        at sample.Main.start(Main.java:64)
        at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(LauncherImpl.java:863)
        at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$174(PlatformImpl.java:326)
        at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
        at java.security.AccessController.doPrivileged(Native Method)
        at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
        at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
        at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
        at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
        ... 1 more
Exception running application sample.Main

Answer 1

im not sure how to read it to get to the base of the issue...

关键部分是这样的:

Caused by: java.lang.NullPointerException
    at sample.Main.start(Main.java:64)

这表明 Main.java 第 64 行抛出了一个 NullPointerException。因此，由于以下行而引发异常:

scene.getStylesheets().add(Main.class.getResource("Login.css").toExternalForm());

具体来说，Main.class.getResource("Login.css") 很可能返回 null。这是因为它找不到 Login.css，几乎可以肯定是因为您没有将其包含在构建中(因此您无法在 IDE 之外成功运行它。)