如何解决小部件处置异常？

Question

In my view I have a selection listener when a window opens. (the view takes the selected project and displays some data according to that project).

The exception occurs when I close and reopen the view. The function that updates the view when a selection is changed in another window works but the view isn't updated after reopening the view.

I have a label with a setText method that gives me this widget disposed exception.

Is this a selection listener problem ? It is necessary to remove all listeners created during the execution when the view is disposed ?

EDIT:

Selection listener code:

final ISelectionListener selectionListener=(new ISelectionListener()
    {

        @Override
        public void selectionChanged(IWorkbenchPart part, ISelection selection) {
            // TODO Auto-generated method stub
            IProject project = null ;
            if(selection==null){
                try {
                    throw new ProjectNotSelected("No selection in Window");
                } catch (ProjectNotSelected e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
            }
            if(selection instanceof IStructuredSelection) {
                Object element = ((IStructuredSelection)selection).getFirstElement();

                if (element instanceof IResource) {
                    project= ((IResource)element).getProject();

                }
                else if (element instanceof IPackageFragmentRoot) {
                    IJavaProject jProject = ((IPackageFragmentRoot)element).getJavaProject();
                    project = jProject.getProject();
                }
                else if (element instanceof IJavaElement) {
                    IJavaProject jProject= ((IJavaElement)element).getJavaProject();
                    project = jProject.getProject();
                }
                else{

                    try {
                        throw new ProjectNotSelected("case 1");
                    } catch (ProjectNotSelected e1) {
                        // TODO Auto-generated catch block
                        e1.printStackTrace();
                    }

                }

            }
            else{
                try {
                    throw new ProjectNotSelected("case 2");
                } catch (ProjectNotSelected e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
            }
            if(project!=null)
            {


                String projectName=project.getName();
                projectNameLabel.setText("Project: "+projectName);



            }
        }
    });

Function that adds the selection listener:

public void newGetCurrentProject(final ISelectionListener selectionListener)
    {   

        IWorkbench workbench = PlatformUI.getWorkbench();

        final IWorkbenchWindow window =workbench.getActiveWorkbenchWindow() ;
        final IPartService pS=window.getPartService();


        pS.addPartListener(new IPartListener()
        {
            @Override
            public void partActivated(IWorkbenchPart part) {
                // TODO Auto-generated method stub              window.getSelectionService().addSelectionListener("org.eclipse.jdt.ui.PackageExplorer",selectionListener);  
            }
            @Override
            public void partBroughtToTop(IWorkbenchPart part) {
                // TODO Auto-generated method stub

            }

            @Override
            public void partClosed(IWorkbenchPart part) {
                // TODO Auto-generated method stub
                                window.getSelectionService().removeSelectionListener("org.eclipse.jdt.ui.PackageExplorer",selectionListener);

            }
        @Override
            public void partDeactivated(IWorkbenchPart part) {
                // TODO Auto-generated method stub


            }

            @Override
            public void partOpened(IWorkbenchPart part) {
                // TODO Auto-generated method stub
                window.getSelectionService().addSelectionListener("org.eclipse.jdt.ui.PackageExplorer",selectionListener);
                }

        });

Stack trace:

org.eclipse.swt.SWTException: Widget is disposed
    at org.eclipse.swt.SWT.error(SWT.java:4361)
    at org.eclipse.swt.SWT.error(SWT.java:4276)
    at org.eclipse.swt.SWT.error(SWT.java:4247)
    at org.eclipse.swt.widgets.Widget.error(Widget.java:468)
    at org.eclipse.swt.widgets.Widget.checkWidget(Widget.java:340)
    at org.eclipse.swt.widgets.Label.setText(Label.java:386)
    at com.warnings.compilation.views.TabViewer$2.selectionChanged(TabViewer.java:260)
    at org.eclipse.ui.internal.AbstractPartSelectionTracker$1.run(AbstractPartSelectionTracker.java:119)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.core.runtime.Platform.run(Platform.java:857)
    at org.eclipse.ui.internal.AbstractPartSelectionTracker.fireSelection(AbstractPartSelectionTracker.java:117)
    at org.eclipse.ui.internal.WindowPartSelectionTracker$1.selectionChanged(WindowPartSelectionTracker.java:38)
    at org.eclipse.ui.internal.AbstractPartSelectionTracker$1.run(AbstractPartSelectionTracker.java:119)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.core.runtime.Platform.run(Platform.java:857)
    at org.eclipse.ui.internal.AbstractPartSelectionTracker.fireSelection(AbstractPartSelectionTracker.java:117)
    at org.eclipse.ui.internal.PagePartSelectionTracker$1.selectionChanged(PagePartSelectionTracker.java:49)
    at org.eclipse.jface.viewers.Viewer$2.run(Viewer.java:164)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.ui.internal.JFaceUtil$1.run(JFaceUtil.java:49)
    at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:175)
    at org.eclipse.jface.viewers.Viewer.fireSelectionChanged(Viewer.java:162)
    at org.eclipse.jface.viewers.StructuredViewer.updateSelection(StructuredViewer.java:2188)
    at org.eclipse.jface.viewers.StructuredViewer.handleSelect(StructuredViewer.java:1211)
    at org.eclipse.jface.viewers.StructuredViewer$4.widgetSelected(StructuredViewer.java:1241)
    at org.eclipse.jface.util.OpenStrategy.fireSelectionEvent(OpenStrategy.java:239)
    at org.eclipse.jface.util.OpenStrategy.access$4(OpenStrategy.java:233)
    at org.eclipse.jface.util.OpenStrategy$1.handleEvent(OpenStrategy.java:403)
    at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1053)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4169)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3758)
    at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2701)
    at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2665)
    at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2499)
    at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:679)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
    at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:668)
    at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
    at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:124)
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
    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:353)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:180)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:629)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1438)
    at org.eclipse.equinox.launcher.Main.main(Main.java:1414)

The selection listener is placed in createPartControl.

The problem occurs on this line:

projectNameLabel.setText("Project: "+projectName);

Answer 1

When you add a selection listener in your view part you must remove the listener when your view closes. Something like:

public classs MyView extends ViewPart
{
  private ISelectionListener myListener;

  @Override
  public void createPartControl(final Composite parent)
  {
    myListener = .... create listener

    ISelectionService selService = ... get selection serivce

    selService.addSelectionListener(myListener);
  }


  @Override
  public void dispose()
  {
    if (myListener != null)
     {
       ISelectionService selService = ... get selection serivce

       selService.removeSelectionListener(myListener);

       myListener = null;
     }

    super.dispose();
  }
}