小程序EDT中运行I/O的问题答案

【问题标题】：Problems in running I/O in EDT of applet小程序EDT中运行I/O的问题
【发布时间】：2012-11-20 09:02:06
【问题描述】：

我们的小程序源代码有点像意大利面条（写于 2000 年，当时是 Java 1.3），我们希望将其重新编译为 Java 1.6 或 1.7。

当我测试它时，大部分 Swing 都可以，但过了一段时间，出现了 Exception，这是 EDT 异常。具体来说，当拖动事件完成时，会出现一系列 EDT 异常。

这与在ActionListeners 中对 I/O 部分进行编码有关吗？因为我已经读到在动作侦听器中编写 I/O 操作是不好的，EDT 在执行动作时执行该操作。

编辑：

这是反复出现的异常

Exception in thread "AWT-EventQueue-3" java.lang.NullPointerException
    at javax.swing.BufferStrategyPaintManager.flushAccumulatedRegion(Unknown Source)
    at javax.swing.BufferStrategyPaintManager.copyArea(Unknown Source)
    at javax.swing.RepaintManager.copyArea(Unknown Source)
    at javax.swing.JViewport.blitDoubleBuffered(Unknown Source)
    at javax.swing.JViewport.windowBlitPaint(Unknown Source)
    at javax.swing.JViewport.setViewPosition(Unknown Source)
    at javax.swing.plaf.basic.BasicScrollPaneUI$Handler.vsbStateChanged(Unknown Source)
    at javax.swing.plaf.basic.BasicScrollPaneUI$Handler.stateChanged(Unknown Source)
    at javax.swing.DefaultBoundedRangeModel.fireStateChanged(Unknown Source)
    at javax.swing.DefaultBoundedRangeModel.setRangeProperties(Unknown Source)
    at javax.swing.DefaultBoundedRangeModel.setValue(Unknown Source)
    at javax.swing.JScrollBar.setValue(Unknown Source)
    at javax.swing.plaf.basic.BasicScrollBarUI$TrackListener.setValueFrom(Unknown Source)
    at javax.swing.plaf.basic.BasicScrollBarUI$TrackListener.mouseDragged(Unknown Source)
    at java.awt.Component.processMouseMotionEvent(Unknown Source)
    at javax.swing.JComponent.processMouseMotionEvent(Unknown Source)
    at java.awt.Component.processEvent(Unknown Source)
    at java.awt.Container.processEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(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.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue$2.run(Unknown Source)
    at java.awt.EventQueue$2.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)

【问题讨论】：

这很可能是由于非 EDT 线程访问 UI 代码。 UI 代码只能由 EDT 访问。关于 IO，EDT 应该很少这样做 - 查看SwingWorker 的 IO 代码。
拖动操作如何导致 I/O？如果是为了“拖动时显示的图标”之类的东西，那么应该在启动时加载图标。
异常是由拖动滚动条或使用拖动动作调整表格列大小引起的...我添加了异常堆栈..谢谢
这是不是和jar包没有打包的applet有关..因为我们所做的就是将class文件直接嵌入到html文件中

标签： java swing io applet event-dispatch-thread

【解决方案1】：

我猜这与java插件的版本有关。在 java 1.6_10 中，这个插件的新版本发布了，我只是禁用了控制面板中的 java 中的选项进阶->Java插件->启用下一代Java插件

当我禁用它时，这个没有明显行为的重复错误不再出现。

我想这也与我们在 Java 1.3 时代编写的代码有关。

【讨论】：