path = '/Users/zhaozhaoyan/Desktop/zymatlab';
filenames = getFilenames(path)
fig = uifigure('Position',[500,500,200,200]);
dd = uidropdown(fig, ...    
    'Position',[50,120,100,30], ...   
    'Items',filenames);
    btn = uibutton(fig, ...   
        'Position',[50,160,100,30], ...    
        'Text','Refresh', ...
        'ButtonPushedFcn',@(btn,event)refreshListsWhenBtnPushed(btn,dd,path))
    
    function filenames = getFilenames(path)
    files = dir(path);
    files = struct2table(files);
    filenames = files.name;
    isvalid = ~ismember(filenames,'.')&~ismember(filenames,'..');
    filenames = filenames(isvalid);
     end
        
    function refreshListsWhenBtnPushed( btn,dd,path)
    dd.Items = getFilenames(path);
    end

