Question

我正在为AP计算机科学决赛制作计算器。我使用Jigloo在Eclipse中构建了GUI，我很快就尝试了解Action Listeners，这样你就可以点击按钮来显示数字。当我开始输入实际代码进行计算时，问题就开始出现了。我一直收到以下错误：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at NewJFrame.<init>(NewJFrame.java:82)
at NewJFrame$1.run(NewJFrame.java:73)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$000(Unknown Source)
at java.awt.EventQueue$1.run(Unknown Source)
at java.awt.EventQueue$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

我对Java很陌生，我以前从未尝试过这样的项目。我很乐意，如果你们能帮助我解决这个问题。这是我的实际代码的链接，由于某种原因它不适合代码框：Link to code

Answer 1

在调用构造函数底部的initGUI()之前，不会分配按钮变量。所以，当你这样做时：

jButton3.addActionListener(new ListenToOne());

...... Java看到了这个：

null.addActionListener(new ListenToOne());

......这显然是一个问题。

“线程中的异常”AWT-EventQueue-0“java.lang.NullPointerException”。我不知道我做错了什么

1 个答案: