Question

启动以下应用程序失败，并显示java.lang.NoSuchMethodException: dev.buildingdragons.dragon.Dragon$.<init>()（在下面找到完整的堆栈跟踪）。

在我看来，似乎缺少构造函数，但是哪一个呢？为什么？

我现在确实有像ScalaFX这样的项目，但是在使用它们之前，我想完全了解正在发生的事情，所以我真的想创建一个行走骨架。

环境：

Windows 10专业版
IntelliJ IDEA Ultimate 2019.1.2
OpenJDK 64位服务器VM Zulu11.2 + 3（内部版本11.0.1 + 13-LTS，混合模式）

Dragon.scala：

package dev.buildingdragons.dragon

import javafx.application.{Application, Platform}
import javafx.scene.Scene
import javafx.scene.control.Button
import javafx.stage.Stage

object Dragon extends Application {
  def main(args: Array[String]) = Application.launch(args: _*)

  override def start(stage: Stage): Unit = {
    val scene = new Scene(new Button("Test"))

    stage.setTitle("Hello, Dragon!")
    stage.setScene(scene)
    stage.showAndWait()

    Platform.exit()
  }
}

build.gradle：

plugins {
    id 'scala'
    id 'org.openjfx.javafxplugin' version '0.0.7'
}

compileScala.targetCompatibility = 1.8

// In this section you declare where to find the dependencies of your project
repositories {
    mavenCentral()
}

dependencies {
    compile 'org.scala-lang:scala-library:2.12.8'
    compile 'org.scalafx:scalafx_2.12:11-R16'
}

javafx {
    version = "11.0.2"
    modules = ['javafx.controls']
}

完整堆栈跟踪：

Exception in Application constructor
Exception in thread "main" java.lang.RuntimeException: Unable to construct Application instance: class dev.buildingdragons.dragon.Dragon$
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:890)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:195)
    at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: java.lang.NoSuchMethodException: dev.buildingdragons.dragon.Dragon$.<init>()
    at java.base/java.lang.Class.getConstructor0(Class.java:3350)
    at java.base/java.lang.Class.getConstructor(Class.java:2152)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$8(LauncherImpl.java:801)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:455)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:428)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:427)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:174)
    ... 1 more

编辑：如eugene-ryzhikov的建议，我修改了Dragon.scala：

package dev.buildingdragons.dragon

import javafx.application.{Application, Platform}
import javafx.scene.Scene
import javafx.scene.control.Button
import javafx.stage.Stage

class Dragon extends Application {
  override def start(stage: Stage): Unit = {
    val scene = new Scene(new Button("Test"))

    stage.setTitle("Hello, Dragon!")
    stage.setScene(scene)
    stage.showAndWait()

    Platform.exit()
  }
}

object Dragon {
  def main(args: Array[String]) = Application.launch(classOf[Dragon],  args: _*)
}

这解决了最初的问题，但是现在我遇到了我担心的问题：Java的Project Jigsaw：

Exception in Application start method
java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:464)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:363)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at java.base/sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:1051)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:900)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:195)
    at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: java.lang.IllegalAccessError: superclass access check failed: class com.sun.javafx.scene.control.ControlHelper (in unnamed module @0x4e08e183) cannot access class com.sun.javafx.scene.layout.RegionHelper (in module javafx.graphics) because module javafx.graphics does not export com.sun.javafx.scene.layout to unnamed module @0x4e08e183
    at java.base/java.lang.ClassLoader.defineClass1(Native Method)
    at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1016)
    at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:174)
    at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:802)
    at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:700)
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:623)
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
    at javafx.scene.control.Control.<clinit>(Control.java:86)
    at dev.buildingdragons.dragon.Dragon.start(Dragon.scala:10)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:846)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:455)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:428)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:427)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:174)
    ... 1 more
Exception running application dev.buildingdragons.dragon.Dragon

我认为这是由于Scala在编译时不强制执行模块限制，而JVM在运行时执行了模块限制。

Answer 1

该错误是对象中使用start方法造成的。使用Dragon对象中的main方法将其移动到新的Dragon类。还可以使用launch方法来传递应用程序类。

OpenJFX应用程序无法使用Scala启动

1 个答案: