ChangeHandler themeSelectionHandler = new ChangeHandler() {
@Override
public void onChange(ChangeEvent event) {
clearEditArea();
Long selectedContentId = Long.valueOf(themeListBox.getSelectedItemValue());
Theme selectedContent = idToContentMap.get(selectedContentId);
nameBox.setText(selectedContent.getName());
deleteButton.setEnabled(true);
}
};
themeListBox.addChangeHandler(themeSelectionHandler);