无法构造javafx.application.Application实例

Question

我正在尝试来自Oracle站点fxml tutorial的JavaFX教程。

package fxml;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

class Main extends Application {

    public Main() {}

    @Override
    public void start(Stage stage) throws Exception {
        Parent root = FXMLLoader.load(getClass().getResource("welcome.fxml"));

        Scene scene = new Scene(root);

        stage.setTitle("FXML UI");
        stage.setScene(scene);
        stage.show();
    }

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

}

这是我不断得到的例外。应用程序不会显示在屏幕上。我从另一个堆栈溢出答案中执行了非args Main()构造函数，但它没有修复它。

Exception in Application constructor
Exception in thread "main" java.lang.RuntimeException: Unable to construct Application instance: class fxml.Main
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:884)
    at com.sun.javafx.application.LauncherImpl.access$000(LauncherImpl.java:56)
    at com.sun.javafx.application.LauncherImpl$1.run(LauncherImpl.java:158)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalAccessException: Class com.sun.javafx.application.LauncherImpl$7 can not access a member of class fxml.Main with modifiers "public"
    at sun.reflect.Reflection.ensureMemberAccess(Reflection.java:101)
    at java.lang.reflect.AccessibleObject.slowCheckMemberAccess(AccessibleObject.java:295)
    at java.lang.reflect.AccessibleObject.checkAccess(AccessibleObject.java:287)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:398)
    at com.sun.javafx.application.LauncherImpl$7.run(LauncherImpl.java:791)
    at com.sun.javafx.application.PlatformImpl$7.run(PlatformImpl.java:335)
    at com.sun.javafx.application.PlatformImpl$6$1.run(PlatformImpl.java:301)
    at com.sun.javafx.application.PlatformImpl$6$1.run(PlatformImpl.java:298)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl$6.run(PlatformImpl.java:298)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)

Answer 1

class Main extends Application缺少初始public关键字。

此外，public Main() {}也是不必要的。