Add backbutton

main.py

@@ -6,6 +6,7 @@ kivy.require('2.2.1')
 
 from kivy.app import App
 from kivy.uix.boxlayout import BoxLayout
+from kivy.uix.stacklayout import StackLayout
 from kivy.uix.button import Button
 from kivy.uix.label import Label
 from kivy.uix.popup import Popup
@@ -31,7 +32,7 @@ class SingleBridgeScreen(Screen):
         self.sm = sm
         self.tinge = tinge
         self.bridge = bridge
-        self.layout = BoxLayout()
+        self.layout = StackLayout()
         self.add_widget(self.layout)
         self.set_group_buttons()
 
@@ -42,6 +43,14 @@ class SingleBridgeScreen(Screen):
                 size_hint=(1, 0.1),
                 on_press=lambda button: self.press_button(button, group))
             self.layout.add_widget(button)
+        backbutton = Button(
+            text="Back",
+            size_hint=(1, 0.1),
+            on_press=lambda button: self.press_back_button(button, "back"))
+        self.layout.add_widget(backbutton)
+
+    def press_back_button(self, button, group):
+        self.sm.current = "bridge_screen"
 
     def press_button(self, light, button):
         print(light)