In this chapter, we shall build a simple Image Viewer app in Kivy. The code below uses Kivy”s Image widget and buttons for navigation through the list of images in the selected folder. There is also a button which opens a
FileChooser to let the user select different folder to view the images in.

First, we need to build a list of all the image files in the currently selected folder. We use the os.listdir() method for this purpose.

import os
self.idx=0
self.fillist=[]
dir_path = ''.''
for file in os.listdir(dir_path):
   if file.endswith(''.png''):
      self.fillist.append(file)

The construction of app interface involves a vertical box layout, in which the Image object is placed on top and another horizontal box layout holding three buttons.

lo=BoxLayout(orientation=''vertical'')
self.img= Image(source=self.fillist[self.idx])
lo.add_widget(self.img)

hlo=BoxLayout(orientation=''horizontal'', size_hint=(1, .1))
self.b1 = Button(text = ''Dir'', on_press=self.onButtonPress)
self.b2 = Button(text = ''Prev'', on_press=self.previmg)
self.b3 = Button(text = ''Next'', on_press=self.nextimg)

hlo.add_widget(self.b1)
hlo.add_widget(self.b2)
hlo.add_widget(self.b3)
lo.add_widget(hlo)

The Image widget displays the first available image to start with. When the button captioned “Next” is clicked, the index pointing to the filelist is incremented; and when the “Previous” button is clicked, it is decremented, loading the indexed image file in the Image object.

def previmg(self, instance):
   self.idx-=1
   if self.idx<0: self.idx=0
   self.img.source=self.fillist[self.idx]
   
def nextimg(self, instance):
   self.idx+=1
   if self.idx>=len(self.fillist):
self.idx=len(self.fillist)-1
   self.img.source=self.fillist[self.idx]

The third button (captioned Dir) pops up a FileChooser dialog. You can choose the required folder to view.

def onButtonPress(self, button):
   layout=GridLayout(cols=1)
   fw=FileChooserListView(dirselect=True, filters=["!*.sys"])
   fw.bind(on_selection=self.onselect)
   closeButton = Button(
      text = "OK", size_hint=(None, None),
      size=(100,75)
   )
   layout.add_widget(fw)
   layout.add_widget(closeButton)
   self.popup = Popup(
      title=''Choose Folder'', content=layout,
      auto_dismiss=False, size_hint=(None, None),
      size=(400, 400)
   )
   self.popup.open()

Example

Images in the current folder populate the fillist to start with. Here is the complete code −

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.gridlayout import GridLayout
from kivy.uix.label import Label
from kivy.uix.popup import Popup
from kivy.uix.image import Image
from kivy.uix.button import Button
from kivy.uix.filechooser import FileChooserListView
from kivy.core.window import Window

Window.size = (720, 400)

class ImageViewerApp(App):
   def previmg(self, instance):
      self.idx -= 1
      if self.idx < 0: self.idx = 0
      self.img.source = self.fillist[self.idx]

   def nextimg(self, instance):
      self.idx += 1
      if self.idx >= len(self.fillist): self.idx = len(self.fillist) - 1
      self.img.source = self.fillist[self.idx]

   def onButtonPress(self, button):
      layout = GridLayout(cols=1)
      fw = FileChooserListView(dirselect=True, filters=["!*.sys"])
      fw.bind(on_selection=self.onselect)
      closeButton = Button(
         text="OK", size_hint=(None, None), size=(100, 75)
      )
      layout.add_widget(fw)
      layout.add_widget(closeButton)
      self.popup = Popup(
         title=''Choose Folder'', content=layout,
         auto_dismiss=False, size_hint=(None, None), size=(400, 400)
      )
      self.popup.open()
      closeButton.bind(on_press=self.on_close)
      
   def onselect(self, *args):
      print(args[1][0])
      
   def on_close(self, event):
      self.popup.dismiss()
      
   def build(self):
      import os
      self.idx = 0
      self.fillist = []
      dir_path = ''.''
      for file in os.listdir(dir_path):
         if file.endswith(''.png''):
            self.fillist.append(file)
      lo = BoxLayout(orientation=''vertical'')
      self.img = Image(source=self.fillist[self.idx])
      lo.add_widget(self.img)
      
      hlo = BoxLayout(orientation=''horizontal'', size_hint=(1, .1))
      
      self.b1 = Button(text=''Dir'', on_press=self.onButtonPress)
      self.b2 = Button(text=''Prev'', on_press=self.previmg)
      self.b3 = Button(text=''Next'', on_press=self.nextimg)
      hlo.add_widget(self.b1)
      hlo.add_widget(self.b2)
      hlo.add_widget(self.b3)
      lo.add_widget(hlo)
      return lo
ImageViewerApp().run()

Output

When you run this code, it will display the image at index “0” −

Click the navigation buttons to go forward and back. Click the “Dir” button to select a new folder.