从项目首选项存储中删除值

Question

在我的自定义插件中，我在新向导上创建了一些文件夹，并在项目首选项中添加了这些创建文件夹的路径。现在，在删除文件夹时，我需要从商店中删除该路径。为此，我延长了org.eclipse.ltk.core.refactoring.deleteParticipants分机。我还创建了一个扩展Change类的类，并在我写的下面的perform方法中，从首选项中删除键值。

public Change perform(IProgressMonitor pm) throws CoreException {
    System.out.println("called");
    IPath deletedFolderPath = deletedFolder.getProjectRelativePath().makeAbsolute();
    IResource[] roots = {deletedFolder.getProject()};
    String[] fileSearchPatterns = {"*.properties", "*.prefs"};
    FileTextSearchScope searchScope = FileTextSearchScope.newSearchScope(roots, fileSearchPatterns, false);

    String regex = deletedFolderPath.addTrailingSeparator().toString();
    Pattern searchPattern = Pattern.compile(regex);

    TextSearchRequestor requestor = new TextSearchRequestor() {

        public boolean acceptPatternMatch(TextSearchMatchAccess matchAccess) throws CoreException {
            IFile matchedFile = matchAccess.getFile();
            if("prefs".equals(matchedFile.getFileExtension())){
                String prefKey = "";
                try {
                    prefKey = ProjectPreferences.getKeyForValue(regex, deletedFolder.getProject());
                    ProjectPreferences.removeKeyFromStore(prefKey, deletedFolder.getProject());
                    System.out.println("after");
                } 
                catch (BackingStoreException e) {
                    throw new CoreException(null);
                }

            }
            else if(".properties".equals(matchedFile.getFileExtension())) {
            }
            return true;
        }
    };
    TextSearchEngine.create().search(searchScope, requestor, searchPattern, pm);
    return null;
}

但是在删除向导上按“确定”后它会卡在线上。

ProjectPreferences.removeKeyFromStore(prefKey, deletedFolder.getProject())

或更具体地说，用removeKeyFromStore方法

写的flush语句

public static void removeKeyFromStore(String key, IProject project) throws BackingStoreException {
    IEclipsePreferences projPref = getPreferences(project);
    projPref.remove(key);
    projPref.flush();
}

我在这里做错了什么或者其他更好的方法来实现相同的功能。

谢谢！