compass in second screen

flockompass.kv

@@ -1,5 +1,7 @@
 #:import random random.random
 #:import RiseInTransition kivy.uix.screenmanager.RiseInTransition
+#:import facade plyer.compass
+
 
 <RootScreen>:
     MapScreen:
@@ -35,6 +37,7 @@
 
 
 <CompassScreen>:
+    facade: facade
     orientation: 'vertical'
     padding: '20dp'
     spacing: '10dp'
@@ -52,8 +55,21 @@
                     text: 'set destination'
                     on_press: root.manager.current = 'map';
 
-
-        Button:
-            text: str(app.gps_data)
-            on_press: app.ms.cambia()
-                    
+        FloatLayout:
+            canvas:
+                Color:
+                    rgb: .08, .08, .08
+                Rectangle:
+                    size: self.size
+            Image:
+                source: 'rose.png'
+            Image:
+                source: 'needle.png'
+                canvas.before:
+                    PushMatrix
+                    Rotate:
+                        angle: app.needle_angle
+                        axis: 0, 0, 1
+                        origin: self.center
+                canvas.after:
+                    PopMatrix

main.py

@@ -1,21 +1,16 @@
 from plyer import gps
 from kivy.app import App
 from kivy.clock import Clock
-from kivy.properties import DictProperty
+from kivy.properties import DictProperty, NumericProperty
 from kivy.clock import mainthread
 from kivy.utils import platform
+from kivy_garden.mapview import MapView
 
 from kivy.uix.screenmanager import ScreenManager, Screen, RiseInTransition
 
-from kivy_garden.mapview import MapView
-
 from kivy.vector import Vector
 from kivy.animation import Animation
 from math import floor
-import random
-from time import sleep
-
-from pprint import pprint
 
 
 class MapScreen(Screen):
@@ -30,11 +25,13 @@ class FlockompassApp(App):
 
     gps_data = DictProperty()
     session_data = DictProperty()
+    needle_angle = NumericProperty(0)
 
     def dump(self, dt):
         print(dt, self.gps_data, self.session_data)
 
     def set_destination(self):
+        self.compass_enable()
         self.session_data['dest_lat'] = self.ms.ids.centermark.lat
         self.session_data['dest_lon'] = self.ms.ids.centermark.lon
         self.ms.ids.mapview.center_on(self.session_data['dest_lat'],
@@ -59,13 +56,6 @@ class FlockompassApp(App):
     def gps_stop(self):
         gps.stop()
 
-    def on_pause(self):
-        self.gps_stop()
-        return True
-
-    def on_resume(self):
-        self.gps_start(1000, 0)
-
     @mainthread
     def on_location(self, **kwargs):
         self.gps_data = kwargs
@@ -79,6 +69,45 @@ class FlockompassApp(App):
             self.ms.ids.mapview.center_on(self.session_data['dest_lat'],
                                           self.session_data['dest_lon'])
 
+    def get_field(self, dt):
+        needle_angle = 7
+        if self.cs.facade.field != (None, None, None):
+            self.x_calib, self.y_calib, self.z_calib = self.cs.facade.field
+            x, y, z = self.cs.facade.field
+
+            needle_angle = Vector(x, y).angle((0, 1)) + 90.
+
+        # fix animation transition around the unit circle
+        if (self.needle_angle % 360) - needle_angle > 180:
+            needle_angle += 360
+        elif (self.needle_angle % 360) - needle_angle < -180:
+            needle_angle -= 360
+        # add the number of revolutions to the result
+        needle_angle += 360 * floor(self.needle_angle / 360.)
+
+        # animate the needle
+        if self.cs._anim:
+            self.cs._anim.stop(self)
+        self.cs._anim = Animation(needle_angle=needle_angle, d=.2, t='out_quad')
+        self.cs._anim.start(self)
+
+    def compass_enable(self):
+        self.cs.facade.enable()
+        Clock.schedule_interval(self.get_field, 1 / 5.0)
+
+    def compass_disable(self):
+        self.cs.facade.disable()
+        Clock.unschedule(self.get_field)
+
+    def on_pause(self):
+        self.compass_disable()
+        self.gps_stop()
+        return True
+
+    def on_resume(self):
+        self.compass_enable()
+        self.gps_start(1000, 0)
+
     def build(self):
 
         # start GPS
@@ -103,6 +132,8 @@ class FlockompassApp(App):
         screen_manager.add_widget(self.ms)
 
         self.cs = CompassScreen(name='compass')
+        self.cs._anim = None
+        self.cs.p = None
         screen_manager.add_widget(self.cs)
 
         Clock.schedule_interval(self.dump, 2.0)