Java 如何修复应用程序构造函数中的异常
我是Javafx新手,我刚刚下载了JDK12并遵循了一个教程,它对我有效,但对我不起作用(我使用模块要求Javafx.controls) 代码如下: 在我的主课上: 我在SOFlow尝试了很多解决方案,但没有结果,我尝试了: 1) 将公共关键字添加到我的类 2) 删除了主方法 还没有工作帮助吗Java 如何修复应用程序构造函数中的异常,java,javafx,Java,Javafx,我是Javafx新手,我刚刚下载了JDK12并遵循了一个教程,它对我有效,但对我不起作用(我使用模块要求Javafx.controls) 代码如下: 在我的主课上: 我在SOFlow尝试了很多解决方案,但没有结果,我尝试了: 1) 将公共关键字添加到我的类 2) 删除了主方法 还没有工作帮助吗 package com.teachersdunet.hellojavafx; import javafx.application.Application; import javafx.stage.Sta
package com.teachersdunet.hellojavafx;
import javafx.application.Application;
import javafx.stage.Stage;
public class HelloApp extends Application {
public static void main(String[] args) {
Application.launch(args);
}
@Override
public void start(Stage primaryStage) throws Exception {
}
}
下面是执行后的错误:
Exception in Application constructor
Exception in thread "main" 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:567)
at java.base/sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:1051)
Caused by: java.lang.RuntimeException: Unable to construct Application instance: class com.teachersdunet.hellojavafx.HelloApp
at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:890)
at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:195)
at java.base/java.lang.Thread.run(Thread.java:835)
Caused by: java.lang.IllegalAccessException: class com.sun.javafx.application.LauncherImpl (in module javafx.graphics) cannot access class com.teachersdunet.hellojavafx.HelloApp (in module com.teachersdunet.hellojavafx) because module com.teachersdunet.hellojavafx does not export com.teachersdunet.hellojavafx to module javafx.graphics
at java.base/jdk.internal.reflect.Reflection.newIllegalAccessException(Reflection.java:376)
at java.base/java.lang.reflect.AccessibleObject.checkAccess(AccessibleObject.java:639)
at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:490)
at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$8(LauncherImpl.java:802)
at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:455)
at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:428)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:389)
at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$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.gtk.GtkApplication._runLoop(Native Method)
at javafx.graphics/com.sun.glass.ui.gtk.GtkApplication.lambda$runLoop$11(GtkApplication.java:277)
... 1 more
stacktrace中几乎提到了解决方案;问题的范围缩小到可以告诉您缺少的导出:
...
Caused by: java.lang.IllegalAccessException: class com.sun.javafx.application.LauncherImpl (in module javafx.graphics) cannot access class com.teachersdunet.hellojavafx.HelloApp (in module com.teachersdunet.hellojavafx) because module com.teachersdunet.hellojavafx does not export com.teachersdunet.hellojavafx to module javafx.graphics
...
将以下行添加到com.teachersdunet.hellojavafx
模块:
module com.teachersdunet.hellojavafx {
...
exports com.teachersdunet.hellojavafx;
}
或者仅授予对单个模块的访问权限:
module com.teachersdunet.hellojavafx {
...
exports com.teachersdunet.hellojavafx to javafx.graphics;
}
您会遇到这样的错误,因为您没有在start方法中调用任何东西。您必须设置
场景
,并提供FXML
文件的目录
我已经更正了你的代码
package com.teachersdunet.hellojavafx;
import javafx.application.Application;
import javafx.stage.Stage;
public class HelloApp extends Application {
@Override
public void start(Stage primaryStage) throws Exception {
try {
Parent root = FXMLLoader.load(getClass().getResource("directory_of_your_fxml_file"));
Scene scene = new Scene(root);
primaryStage.setScene(scene);
primaryStage.show();
} catch(Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
}
我希望这会有所帮助。请参阅仅在显示任何内容时有所帮助,前提是他/她正在使用fxml和合适的控制器。无法解决由于项目设置不正确而引发的错误。有关修复方法,请参阅。次要挑剔:严格来说,class.getResource的参数是一个包名(绝对或相对解析),而不是一个目录名。