public boolean isOneSelected() {
        return _selected.size() == 1;
    }
@param file        file that should me displayed
@param isSelected  whether file is selected when _enableMultiple is set to true
@param isFocused   @deprecated! use fileListItemFocusedDrawable attribute instead
@param convertView see {@link ArrayAdapter#getView(int, View, ViewGroup)}
@param parent      see {@link ArrayAdapter#getView(int, View, ViewGroup)}
@param inflater    a layout inflater with the FileChooser theme wrapped context
@return your custom row item view
android-file-chooser/src/main/java/com/obsez/android/lib/filechooser/tool/DirAdapter.java