有人知道如何开始在 Java Swing 中调试这个错误吗？
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.BoxLayout.preferredLayoutSize(BoxLayout.java:282)
at java.awt.Container.preferredSize(Container.java:1599)
at java.awt.Container.getPreferredSize(Container.java:1584)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1636)
at java.awt.BorderLayout.layoutContainer(BorderLayout.java:804)
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.validate(Container.java:1480)
at javax.swing.plaf.basic.BasicTabbedPaneUI.ensureCurrentLayout(BasicTabbedPaneUI.java:1429)
at javax.swing.plaf.basic.BasicTabbedPaneUI.getTabBounds(BasicTabbedPaneUI.java:1449)
at javax.swing.plaf.synth.SynthTabbedPaneUI.setRolloverTab(SynthTabbedPaneUI.java:491)
at javax.swing.plaf.basic.BasicTabbedPaneUI$TabbedPaneLayout.layoutContainer(BasicTabbedPaneUI.java:2384)
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.validate(Container.java:1480)
at javax.swing.plaf.basic.BasicTabbedPaneUI.ensureCurrentLayout(BasicTabbedPaneUI.java:1429)
at javax.swing.plaf.basic.BasicTabbedPaneUI.getTabBounds(BasicTabbedPaneUI.java:1449)
at javax.swing.plaf.synth.SynthTabbedPaneUI.setRolloverTab(SynthTabbedPaneUI.java:498)
at javax.swing.plaf.basic.BasicTabbedPaneUI.setRolloverTab(BasicTabbedPaneUI.java:558)
at javax.swing.plaf.basic.BasicTabbedPaneUI.access$2000(BasicTabbedPaneUI.java:37)
at javax.swing.plaf.basic.BasicTabbedPaneUI$Handler.mouseMoved(BasicTabbedPaneUI.java:3645)
at java.awt.Component.processMouseMotionEvent(Component.java:6333)
at javax.swing.JComponent.processMouseMotionEvent(JComponent.java:3285)
at java.awt.Component.processEvent(Component.java:6057)
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:4251)
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)
它是从 BoxLayout 中的这个方法抛出的(行 size = ...)
public Dimension preferredLayoutSize(Container target) {
Dimension size;
synchronized(this) {
checkContainer(target);
checkRequests();
size = new Dimension(xTotal.preferred, yTotal.preferred);
}
最佳答案
扩展布局管理器以提供同步不太可能有效。确认所有 GUI 组件都是在 the event dispatch thread 上构建的.同样，验证 所有 数据模型是否已在 the event dispatch thread 上更新, 使用 invokeLater()或 SwingWorker .
关于java - BoxLayout 中的 NullPointerException，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/6709150/