Edit

import java.util.HashSet;

import java.util.Set;

import org.apache.commons.lang.StringUtils;

    private Set<NamedArea> areas = new HashSet<>();

    public Set<NamedArea> getAreas() {

        return areas;

    public void setAreas(Set<NamedArea> areas) {

        this.areas = areas;

        textAreaText.setText(StringUtils.join(areas, ", "));

        this.areas = null;

import java.util.Arrays;

import org.eclipse.jface.dialogs.Dialog;

import org.eclipse.jface.viewers.StyledString.Styler;

import org.eclipse.swt.graphics.TextStyle;

import org.eclipse.swt.widgets.Control;

import eu.etaxonomy.cdm.api.service.IVocabularyService;

import eu.etaxonomy.cdm.model.common.TermType;

import eu.etaxonomy.cdm.model.common.TermVocabulary;

import eu.etaxonomy.taxeditor.preference.wizard.AreaLabelProvider;

import eu.etaxonomy.taxeditor.preference.wizard.CheckBoxTreeComposite;

import eu.etaxonomy.taxeditor.preference.wizard.DistributionContentProvider;

                AreasSelectionDialog areasSelectionDialog = new AreasSelectionDialog(composite.getShell(), composite.getAreas());

                areasSelectionDialog.open();

                Set<NamedArea> selectedAreas = areasSelectionDialog.getSelectedAreas();

                if(selectedAreas!=null){

                    composite.setAreas(selectedAreas);

                    dirty.setDirty(true);

            composite.setAreas(geoFilter);

        Set<NamedArea> areas = composite.getAreas();

    private class AreasSelectionDialog extends Dialog{

        private CheckBoxTreeComposite treeComposite;

        private Set<NamedArea> selectedAreas = new HashSet<>();

        private Collection<TermVocabulary<NamedArea>> namedAreas;

        protected AreasSelectionDialog(Shell parentShell, Set<NamedArea> selectedAreas) {

            super(parentShell);

            this.selectedAreas = selectedAreas;

            this.namedAreas = CdmStore.getService(IVocabularyService.class).findByTermType(TermType.NamedArea, null);

        }

        @Override

        protected Control createDialogArea(Composite parent) {

            Styler styler = new Styler() {

                @Override

                public void applyStyles(TextStyle textStyle) {

                    textStyle.foreground = Display.getCurrent().getSystemColor(SWT.COLOR_BLACK);

                }

            };

            treeComposite = new CheckBoxTreeComposite(parent, new DistributionContentProvider(), new AreaLabelProvider(styler), SWT.NONE);

            treeComposite.getViewer().setInput(namedAreas);

            treeComposite.getViewer().setCheckedElements(selectedAreas.toArray());

            return treeComposite;

        }

        @Override

        protected void configureShell(Shell newShell) {

            super.configureShell(newShell);

            newShell.setText("Choose areas");

        }

        @Override

        protected void okPressed() {

            selectedAreas.clear();

            selectedAreas = new HashSet(Arrays.asList(treeComposite.getViewer().getCheckedElements()));

            super.okPressed();

        }

        @Override

        protected boolean isResizable() {

            return true;

        }

        public Set<NamedArea> getSelectedAreas(){

            return selectedAreas;

        }

    }

/**

 * Copyright (C) 2018 EDIT

 * European Distributed Institute of Taxonomy

 * http://www.e-taxonomy.eu

 *

 * The contents of this file are subject to the Mozilla Public License Version 1.1

 * See LICENSE.TXT at the top of this package for the full license terms.

 */

package eu.etaxonomy.taxeditor.preference.wizard;

import org.eclipse.jface.viewers.CheckboxTreeViewer;

import org.eclipse.jface.viewers.IBaseLabelProvider;

import org.eclipse.jface.viewers.IContentProvider;

import org.eclipse.swt.SWT;

import org.eclipse.swt.layout.GridData;

import org.eclipse.swt.layout.GridLayout;

import org.eclipse.swt.widgets.Composite;

import org.eclipse.swt.widgets.Tree;

import org.eclipse.swt.widgets.TreeItem;

/**

 * @author pplitzner

 * @since Oct 26, 2018

 *

 */

public class CheckBoxTreeComposite extends Composite {

    private CheckboxTreeViewer viewer;

    public CheckBoxTreeComposite(Composite parent, IContentProvider contentProvider, IBaseLabelProvider labelProvider, int style) {

        super(parent, style);

        Composite composite = new Composite(parent, SWT.NULL);

        composite.setLayout(new GridLayout());

        Tree tree = new Tree(parent, SWT.BORDER | SWT.CHECK);

        tree.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));

        tree.addListener(SWT.Selection, event -> {

            if (event.detail == SWT.CHECK) {

                TreeItem item = (TreeItem) event.item;

                boolean checked = item.getChecked();

                checkItems(item, checked);

                checkPath(item.getParentItem(), checked, false);

            }

        });

        viewer = new CheckboxTreeViewer(tree);

        viewer.setContentProvider(contentProvider);

        viewer.setLabelProvider(labelProvider);

    }

    private void checkPath(TreeItem item, boolean checked, boolean grayed) {

        if (item == null) {

            return;

        }

        if (grayed) {

            checked = true;

        } else {

            int index = 0;

            TreeItem[] items = item.getItems();

            while (index < items.length) {

                TreeItem child = items[index];

                if (child.getGrayed() || checked != child.getChecked()) {

                    checked = grayed = true;

                    break;

                }

                index++;

            }

        }

        item.setChecked(checked);

        item.setGrayed(grayed);

        checkPath(item.getParentItem(), checked, grayed);

    }

    private void checkItems(TreeItem item, boolean checked) {

        item.setGrayed(false);

        item.setChecked(checked);

        TreeItem[] items = item.getItems();

        for (int i = 0; i < items.length; i++) {

            checkItems(items[i], checked);

        }

    }

    public CheckboxTreeViewer getViewer() {

        return viewer;

    }

}