Unhandled event loop exception

Question

org.eclipse.swt.SWTException: Widget is disposed
 at org.eclipse.swt.SWT.error(SWT.java:3884)
 at org.eclipse.swt.SWT.error(SWT.java:3799)
 at org.eclipse.swt.SWT.error(SWT.java:3770)
 at org.eclipse.swt.widgets.Widget.error(Widget.java:450)
 at org.eclipse.swt.widgets.Widget.checkWidget(Widget.java:388)
 at org.eclipse.swt.widgets.Composite.setFocus(Composite.java:1249)
 at org.eclipse.compare.CompareViewerSwitchingPane.setFocus(CompareViewerSwitchingPane.java:363)
 at org.eclipse.compare.CompareEditorInput.setFocus2(CompareEditorInput.java:860)
 at org.eclipse.compare.internal.CompareEditor.setFocus(CompareEditor.java:499)
 at org.eclipse.ui.internal.PartPane.setFocus(PartPane.java:332)
 at org.eclipse.ui.internal.EditorPane.setFocus(EditorPane.java:127)
 at org.eclipse.ui.internal.presentations.PresentablePart.setFocus(PresentablePart.java:190)
 at org.eclipse.ui.internal.presentations.util.TabbedStackPresentation$1.handleEvent(TabbedStackPresentation.java:94)
 at org.eclipse.ui.internal.presentations.util.AbstractTabFolder.fireEvent(AbstractTabFolder.java:270)
 at org.eclipse.ui.internal.presentations.util.AbstractTabFolder.fireEvent(AbstractTabFolder.java:275)
 at org.eclipse.ui.internal.presentations.util.AbstractTabFolder.handleMouseDown(AbstractTabFolder.java:345)
 at org.eclipse.ui.internal.presentations.util.AbstractTabFolder$3.mouseDown(AbstractTabFolder.java:79)
 at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:179)
 at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
 at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1176)
 at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3493)
 at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3112)
 at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2405)
 at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2369)
 at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2221)
 at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:500)
 at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
 at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:493)
 at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
 at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:113)
 at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:194)
 at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
 at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
 at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:368)
 at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:597)
 at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:559)
 at org.eclipse.equinox.launcher.Main.basicRun(Main.java:514)
 at org.eclipse.equinox.launcher.Main.run(Main.java:1311)

Answer 1

Seems that you made widget.setFocus(..) over a widget variable referencing a previously dispatched widget (widget.dispose())... Check what you are assigning to the var...