Python kivy图像不显示

我是新来的基维。我想做的是显示目录中的所有图像，用户可以向下滚动浏览它们

我遇到了一个问题，对于目录中的一个文件夹，所有图像都显示为白色矩形，我不明白为什么。另一个目录中的图像显示良好。。。以下是源代码：

    class vAll(Screen):

    def __init__ (self,**kwargs):
        super (vAll, self).__init__(**kwargs)

 #       os.chdir("/Users/User/Documents/dev/engineerappcopy/VGimages")
        popup = Popup(title='View all', size_hint=(1,1), auto_dismiss=False)
        ims = []

        directory_list = list()
        for root, dirs, files in  os.walk("/Users/User/Documents/dev/engineerappcopy/VGimages", topdown=False):
            for name in dirs:
                directory_list.append(os.path.join(root, name))

        print directory_list
        #this layout is the child widget for the main popup
        layout1 = StackLayout(orientation='lr-bt')

            #this button is a child of layout1
        closebutton = Button(text='back', size_hint=(0.8,0.05))
        closebutton.bind(on_press=self.changer)
        sz = 1
        for d in directory_list:
            os.chdir(d)
            for fn in glob.glob("*.png"):
        #return Image(source=fn,size=(10,10))
                ims.append(fn)
            for im in ims:
                print im
                i = AsyncImage(source=im)
                sz = sz + 1
        #another child of layout1 and this is the scrollview which will have a custom draggable scrollbar
        scrlv = ScrollView(size_hint=(0.9,0.95))
        layout2 = GridLayout(cols=2, size_hint_y= sz/10+4)
        layout2.bind(minimum_height=layout2.setter('height'))

        for im in ims:
          i = Image(source=im)
          layout2.add_widget(i)
        scrlv.add_widget(layout2)
        layout1.add_widget(closebutton)
        layout1.add_widget(scrlv)
        self.add_widget(layout1)


        def scroll_change(self, scrlv, instance, value):
            scrlv.scroll_y = value


    def changer(self,*args):
        self.manager.current = 'home'

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抱歉，这段代码太糟糕了，我只是想把它用到workWhite矩形通常意味着图像路径无效或格式不受支持。抱歉，这段代码太糟糕了，我只是在玩，试图让它工作。白色矩形通常意味着图像路径无效或格式不受支持。