[英]Discover Reason of NullPointerException in Java Native Classes, SynthTreeUI using LAF Nimbus
审阅者注意:这可能是NimbusLookAndFeel中的一个(可能是已知的)错误,并且(至今)尚未解决规范的NPE问题。
我有多个类,但是我不知道异常可能暗示其中的哪个类。
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.plaf.synth.SynthTreeUI.paint(SynthTreeUI.java:382)
at javax.swing.plaf.synth.SynthTreeUI.update(SynthTreeUI.java:269)
at javax.swing.JComponent.paintComponent(JComponent.java:780)
at javax.swing.JComponent.paint(JComponent.java:1056)
at javax.swing.JComponent.paintToOffscreen(JComponent.java:5210)
at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1579)
at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1502)
at javax.swing.RepaintManager.paint(RepaintManager.java:1272)
at javax.swing.JComponent._paintImmediately(JComponent.java:5158)
at javax.swing.JComponent.paintImmediately(JComponent.java:4969)
at javax.swing.RepaintManager$4.run(RepaintManager.java:831)
at javax.swing.RepaintManager$4.run(RepaintManager.java:814)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:814)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:789)
at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:738)
at javax.swing.RepaintManager.access$1200(RepaintManager.java:64)
at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1732)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
如您所见,该异常不会在任何地方链接我的代码。
对于创建最小,完整和可验证的示例,我无法通过我的所有项目,因为该项目很长,并且由于无法找到源代码,因此无法在其上添加任何代码。
我扩展:
从DefaultMutableTreeNode
为了
@Override public String toString()
从DefaultTreeCellRenderer
为了
@Override public Component getTreeCellRendererComponent(JTree tree, Object value, boolean selected, boolean expanded, boolean leaf, int row, boolean hasFocus)
现在的情况是:
//Fails
//javax.swing.UIManager.setLookAndFeel("javax.swing.plaf.nimbus.NimbusLookAndFeel");
//Works
//javax.swing.UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
//Works
//javax.swing.UIManager.setLookAndFeel("com.apple.laf.AquaLookAndFeel");
注意: 我不需要解决方案。 如果不提供代码,那将是不合逻辑的!!!
问题: 我应该在哪里特别寻找问题的根源?
我在JTree中也遇到类似的情况,我的问题的原因是(在线程内部更新JTree),救助是使用SwingWorker。 该解释是基于类似的帖子
https://www.javacodegeeks.com/2012/12/multi-threading-in-java-swing-with-swingworker.html
我不假装提供严格的功能性解决方案或代码,而只是给您一个解决问题的方法。
class SwingWorkerCustomDTO extends SwingWorker<Void, CustomDTO> {
@Override
protected Void doInBackground() throws Exception {
//Initialization and Iterative Operation over JTree
myJTree = new JTree(/**/); // or Set the Model
//someLongTask(arguments);
/*long time/delayed Task that he sometimes performs o operations on JTree.*/
return null;
}
@Override
protected void done() {
//reload or update JTree /*or what you imagine doing*/
//removeOrUpdateTask();
//example
DefaultTreeModel treeModel = ((DefaultTreeModel)myJTree.getModel());
DefaultMutableTreeNode rootTreeNode = (DefaultMutableTreeNode) treeModel.getRoot();
treeModel.reload(rootTreeNode);
}
@Override
protected void process(List<CustomDTO> chunks) {
for (final CustomDTO chunk : chunks) {
//The Operation (Add/Remove/Update) of JTree are performed here!.
switch (chunk.getOperarionType()) {
case ADD_CONSTANT: /*or what you define*/
//Add Node(Object or Objects[]) to Some JTree;
break;
case UPDATE_CONSTANT: /*or what you define*/
//Update Node(Object or Objects[]) to Some JTree;
break;
case REMOVE_CONSTANT:
//Remove Node(Object or Objects[]) from Some JTree;
break;
}
}
}
public void callPublish(CustomDTO customDTO) {
/*I expose a public method to pass arguments that make functionalities
(Add/Remove/Update Node) required in the JTree invoked externally.*/
publish(customDTO);
}
}
在外部,您可以调用自己的自定义课程
swingWorkerCustomDTO.callPublish(
new CustomDTO(int OperationType/*or what you define*/,
Object argument /*or Object[] arguments*/));
CustomDTO
是由您定义的类,其中包含操作(您要做什么),例如int属性,以及所需的另一个属性。
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