Java - NullPointerException开始。Swing错误或错误的实现？
Java - NullPointerException开始。Swing错误或错误的实现？
提问于 2010-12-07 21:03:35
我正在为一家公司开发一个应用程序，该公司以各种方式管理oracle数据库。这个程序是用Java，NetBeans编写的，而且它变得很大。我不会说它写得很好，但我经常回到旧的糟糕的代码，并试图让它尽可能地可读性和oop。
我已经注意到，当我启动程序时，每10次中就有1次得到以下异常：(尽管程序启动并正常工作，即使这些时候也是如此)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.plaf.synth.SynthLabelUI.getMinimumSize(SynthLabelUI.java:199)
at javax.swing.JComponent.getMinimumSize(JComponent.java:1702)
at javax.swing.GroupLayout$ComponentSpring.calculateNonlinkedMinimumSize(GroupLayout.java:2933)
at javax.swing.GroupLayout$ComponentSpring.calculateMinimumSize(GroupLayout.java:2897)
at javax.swing.GroupLayout$Spring.getMinimumSize(GroupLayout.java:1315)
at javax.swing.GroupLayout$ComponentSpring.calculatePreferredSize(GroupLayout.java:2904)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1325)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1604)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1593)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1568)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1325)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1604)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1590)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1568)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1325)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1604)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1593)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1568)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1325)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1604)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1590)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1568)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1325)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1604)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1590)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1568)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1325)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1604)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1588)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1568)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1325)
at javax.swing.GroupLayout.calculateAutopadding(GroupLayout.java:1050)
at javax.swing.GroupLayout.prepare(GroupLayout.java:1037)
at javax.swing.GroupLayout.preferredLayoutSize(GroupLayout.java:857)
at java.awt.Container.preferredSize(Container.java:1599)
at java.awt.Container.getPreferredSize(Container.java:1584)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1624)
at javax.swing.GroupLayout$ComponentSpring.calculateNonlinkedPreferredSize(GroupLayout.java:2944)
at javax.swing.GroupLayout$ComponentSpring.calculateNonlinkedMinimumSize(GroupLayout.java:2930)
at javax.swing.GroupLayout$ComponentSpring.calculateMinimumSize(GroupLayout.java:2897)
at javax.swing.GroupLayout$Spring.getMinimumSize(GroupLayout.java:1315)
at javax.swing.GroupLayout$ComponentSpring.calculatePreferredSize(GroupLayout.java:2904)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1325)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1604)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1593)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1568)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1325)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1604)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1588)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1568)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1325)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1604)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1588)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1568)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1325)
at javax.swing.GroupLayout$SequentialGroup.setValidSize(GroupLayout.java:1972)
at javax.swing.GroupLayout$Group.setSize(GroupLayout.java:1553)
at javax.swing.GroupLayout.calculateAutopadding(GroupLayout.java:1058)
at javax.swing.GroupLayout.layoutContainer(GroupLayout.java:897)
at java.awt.Container.layout(Container.java:1421)
at java.awt.Container.doLayout(Container.java:1410)
at java.awt.Container.validateTree(Container.java:1507)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validate(Container.java:1480)
at java.awt.Window.dispatchEventImpl(Window.java:2473)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
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)我假设这是一个swing bug。这会是我的实现中的一个问题吗？为什么这种情况每10次中就有1次发生，而不是总是发生？我能做些什么来避免它吗？
回答 3
Stack Overflow用户
回答已采纳
发布于 2010-12-07 21:09:58
每10个人中就有1个听起来可能是某个地方的竞争状况。正如@willcodejavaforfood提到的，您需要确保所有GUI更改(包括启动)都在事件分派线程(EDT)上完成。
您可以使用SwingUtilities.invokeAndWait和SwingUtilities.invokeLater来确保代码在EDT上执行。
Stack Overflow用户
发布于 2010-12-07 21:13:58
在SynthDefaultLookup.java的第27行中有这样的内容：
public Object getDefault(JComponent c, ComponentUI ui, String key) {
if (!(ui instanceof SynthUI)) {
Object value = super.getDefault(c, ui, key);
return value;
}
SynthContext context = ((SynthUI)ui).getContext(c);
Object value = context.getStyle().get(context, key); // line 27
context.dispose();
return value;
}..。也许是componentUI的上下文？你有没有一些没有ComponentUI的特殊UI？
(好的，这不是一个答案，我道歉，但这也不是一个评论)
Stack Overflow用户
发布于 2010-12-07 21:09:29
它看起来像是UI提供了一个NullPointerException，但它并不只是在那里和在那里。UI使用的其他东西可能不能正常工作，或者类似的东西。你能在这里发布整个错误和导致它的代码片段吗？
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/4376858
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