Question

我遇到了一个问题，当我运行我的应用程序并单击JMenuBar时，我得到以下异常，我不确定为什么因为异常指向我的代码没有行，这些行都来自JavaLibraries。事件处理程序/ Dispatche上的异常点...所以我猜可能我没有在JMenuBar，JMenu和JMenuItem上设置配置。

基本上是我的代码：

    menubarsita = new JMyMenuBar(); // Instanciate the JMenuBar
    session.buildMenu(menubarsita,this); //Add the JMenu and the JMenuItems
    this.setJMenuBar(menubarsita); // Add the menu bar to the JFrame

添加JMenu和菜单项的代码：

    JMenu archivo = new JMenu(); //Instanciate the JMenu
    archivo.setText("archivo"); // Set Text
    MenuItem arch = new JMenuItem(); //Instanciate the JMenuItem
    arch.setText("lala"); // Set Text
    arch.addActionListener(frame); //Adding the action listener.
    archivo.add(arch); // Adding JMenuItem To JMenu
    menubar.add(archivo);  // Adding JMenu to JMenuBar

异常详细信息：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at        javax.swing.plaf.basic.BasicMenuBarUI$Handler.stateChanged(BasicMenuBarUI.java:176)
at javax.swing.DefaultButtonModel.fireStateChanged(DefaultButtonModel.java:333)
at javax.swing.DefaultButtonModel.setSelected(DefaultButtonModel.java:215)
at javax.swing.JMenu.setSelected(JMenu.java:294)
at javax.swing.JMenu.menuSelectionChanged(JMenu.java:1175)
at javax.swing.MenuSelectionManager.setSelectedPath(MenuSelectionManager.java:100)
at javax.swing.plaf.basic.BasicMenuUI$Handler.mousePressed(BasicMenuUI.java:434)
at java.awt.Component.processMouseEvent(Component.java:6285)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
at java.awt.Component.processEvent(Component.java:6053)
at java.awt.Container.processEvent(Container.java:2041)
at java.awt.Component.dispatchEventImpl(Component.java:4651)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4481)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4577)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4235)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
at java.awt.Container.dispatchEventImpl(Container.java:2085)
at java.awt.Window.dispatchEventImpl(Window.java:2478)
at java.awt.Component.dispatchEvent(Component.java:4481)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:643)
at java.awt.EventQueue.access$000(EventQueue.java:84)
at java.awt.EventQueue$1.run(EventQueue.java:602)
at java.awt.EventQueue$1.run(EventQueue.java:600)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)
at java.awt.EventQueue$2.run(EventQueue.java:616)
at java.awt.EventQueue$2.run(EventQueue.java:614)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:613)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

更新

如果添加JMenu和Menu项的代码重新排列如下，则不会出现异常：

JMenu archivo = new JMenu();
JMenuItem arch = new JMenuItem();
archivo.setText("archivo");
arch.setText("lala");
arch.addActionListener(frame);
archivo.add(arch);
menubar.add(archivo);

线程“AWT-EventQueue-0”中的异常java.lang.NullPointerException

0 个答案: