EDIT

import org.eclipse.swt.events.SelectionAdapter;

import org.eclipse.swt.events.SelectionEvent;

import org.eclipse.swt.layout.GridLayout;

import org.eclipse.swt.widgets.Button;

import org.eclipse.swt.widgets.Combo;

import org.eclipse.swt.widgets.Composite;

import org.eclipse.swt.widgets.Control;

import eu.etaxonomy.cdm.model.metadata.CdmPreference;

import eu.etaxonomy.taxeditor.l10n.Messages;

import eu.etaxonomy.taxeditor.preference.PreferencesUtil;

    protected Boolean isMultilanguageTextEditingCapability;

    protected CdmPreference multiLangugeActivatedPref =null;

    private boolean overrideActivated;

    Combo multiLanguageEditing;

    Button allowOverrideOrderButton;

	@Override

    protected Control createContents(Composite parent) {

	    createSetMultiLanguageTextEditingCapability(parent);

	    Composite result = (Composite) super.createContents(parent);

	    return result;

	}

	private void createSetMultiLanguageTextEditingCapability(Composite parent) {

        //isMultilanguageTextEditingCapability = PreferencesUtil.getBooleanValue(PreferencePredicate.MultiLanguageTextEditing.getKey());

	    getValues();

        final Composite composite = createComposite(parent);

        GridLayout layout = new GridLayout();

        layout.numColumns = 2;

        composite.setLayout(layout);

        multiLanguageEditing = createBooleanCombo(composite, Messages.GeneralPreference_yes, Messages.GeneralPreference_no, PreferencePredicate.MultiLanguageTextEditing, "Allow multi language editing", isAdminPreference);

        int index = 0;

        for (String itemLabel : multiLanguageEditing.getItems()) {

            if (isMultilanguageTextEditingCapability == null && itemLabel.startsWith(Messages.Preference_Use_Default)) {

                multiLanguageEditing.select(index);

                break;

            }

            if (isMultilanguageTextEditingCapability != null && itemLabel.equals(Messages.GeneralPreference_yes) && isMultilanguageTextEditingCapability){

                multiLanguageEditing.select(index);

                break;

            }

            if (isMultilanguageTextEditingCapability != null && itemLabel.equals(Messages.GeneralPreference_no) && !isMultilanguageTextEditingCapability){

                multiLanguageEditing.select(index);

                break;

            }

            index++;

        }

        if (!isAdminPreference && multiLangugeActivatedPref != null){

            multiLanguageEditing.setEnabled(multiLangugeActivatedPref.isAllowOverride());

        }

        multiLanguageEditing.addSelectionListener(this);

        if (isAdminPreference) {

            allowOverrideOrderButton = createAllowOverrideButton(composite);

            allowOverrideOrderButton.setSelection(multiLangugeActivatedPref != null? multiLangugeActivatedPref.isAllowOverride(): true);

            //allowOverrideOrderAreasButton.setEnabled(prefAreaSort != null);

            allowOverrideOrderButton.addSelectionListener(new SelectionAdapter() {

                @Override

                public void widgetSelected(SelectionEvent e) {

                    setApply(true);

                    if (multiLangugeActivatedPref == null){

                        multiLangugeActivatedPref = CdmPreference.NewTaxEditorInstance(PreferencePredicate.MultiLanguageTextEditing, PreferencePredicate.MultiLanguageTextEditing.getDefaultValue() != null ?  PreferencePredicate.MultiLanguageTextEditing.getDefaultValue().toString(): null);

                    }

                    multiLangugeActivatedPref.setAllowOverride(allowOverrideOrderButton.getSelection());

                }

            });

        }

    }

	 @Override

	 public void getValues() {

	        isAdminPreference = false;

	        setPreferenceStore(PreferencesUtil.getPreferenceStore());

	        multiLangugeActivatedPref = PreferencesUtil.getPreferenceFromDB(PreferencePredicate.MultiLanguageTextEditing);

	        overrideActivated = PreferencesUtil.getBooleanValue(

	                PreferencesUtil.prefOverrideKey(PreferencePredicate.MultiLanguageTextEditing.getKey()), true) != null? PreferencesUtil.getBooleanValue(

	                        PreferencesUtil.prefOverrideKey(PreferencePredicate.MultiLanguageTextEditing.getKey()), true):false;

            if (multiLangugeActivatedPref != null) {

                if (multiLangugeActivatedPref.isAllowOverride() ) {

                    if (overrideActivated){

                        isMultilanguageTextEditingCapability = PreferencesUtil.getBooleanValue(PreferencePredicate.MultiLanguageTextEditing.getKey(), true);

                    }

                } else {

                    isMultilanguageTextEditingCapability = multiLangugeActivatedPref.getValue() != null? Boolean.valueOf(multiLangugeActivatedPref.getValue()): null;

                }

            } else {

                if(!overrideActivated){

                    isMultilanguageTextEditingCapability = null;

                }else{

                    isMultilanguageTextEditingCapability = PreferencesUtil.getBooleanValue(PreferencePredicate.MultiLanguageTextEditing.getKey(), true);

                }

                multiLangugeActivatedPref = CdmPreference.NewTaxEditorInstance(PreferencePredicate.MultiLanguageTextEditing, PreferencePredicate.MultiLanguageTextEditing.getDefaultValue() != null ?  PreferencePredicate.MultiLanguageTextEditing.getDefaultValue().toString(): null);

            }

	 }

	 @Override

	 public void widgetSelected(SelectionEvent e) {

        setApply(true);

        if (e.getSource().equals(multiLanguageEditing)) {

            String text = multiLanguageEditing.getText();

            if(text.startsWith(Messages.Preference_Use_Default)){

                isMultilanguageTextEditingCapability = null;

                treeComposite.setEnabled(multiLangugeActivatedPref == null? true: multiLangugeActivatedPref.getValue() != null?Boolean.parseBoolean(multiLangugeActivatedPref.getValue().toString()): true);

                if (!isAdminPreference) {

                    overrideActivated = false;

                }

                return;

            }

            overrideActivated = true;

            if (text.equals(Messages.GeneralPreference_yes)){

                isMultilanguageTextEditingCapability = true;

            }else{

                isMultilanguageTextEditingCapability = false;

            }

            if (isMultilanguageTextEditingCapability != null){

                treeComposite.setEnabled(isMultilanguageTextEditingCapability);

            }else{

                treeComposite.setEnabled(multiLangugeActivatedPref == null? true: multiLangugeActivatedPref.getValue() != null?Boolean.parseBoolean(multiLangugeActivatedPref.getValue().toString()): true);

            }

        }

     }

	@Override

    public boolean performOk() {

        if (!isApply()){

            return true;

        }

        if (isMultilanguageTextEditingCapability!= null){

            PreferencesUtil.setBooleanValue(PreferencePredicate.MultiLanguageTextEditing.getKey(), isMultilanguageTextEditingCapability);

        }

        PreferencesUtil.setBooleanValue(

                PreferencesUtil.prefOverrideKey(PreferencePredicate.MultiLanguageTextEditing.getKey()),

                overrideActivated);

        return super.performOk();

    }