working dynamic graph using matplotlib

main.kv

@@ -1,6 +1,8 @@
 <MyLabel@Label>:
     text: 'Current Temperature: n/a'
-#    on_lastTemperature: self.update_current_temperature_label()
+
+<PlotWidget@Image>:
+    allow_stretch: True
 
 <MainWindow>:
     label_wid: "Temperature Monitor"
@@ -17,5 +19,5 @@
                 text: 'No File Chosen'
             Label:
                 text: 'Data Source'
-        Label:
+        PlotWidget:
-            text: 'Graph placeholder'
+            id: 'mainplot'

main.py

@@ -1,13 +1,23 @@
 import kivy
 from kivy.app import App
 from kivy.clock import Clock
+import kivy.core.image
+from kivy.core.image.img_pygame import ImageLoaderPygame
+import kivy.graphics.texture
 from kivy.logger import Logger
-from kivy.properties import ObjectProperty, StringProperty
+from kivy.properties import ListProperty, NumericProperty, ObjectProperty, StringProperty
 from kivy.uix.boxlayout import BoxLayout
 from kivy.uix.floatlayout import FloatLayout
+from kivy.uix.image import Image
 from kivy.uix.label import Label
 import kivy.lang
+import numpy
+import matplotlib
+matplotlib.use('Agg')
+import matplotlib.image
+import matplotlib.pyplot
 import Queue
+import StringIO
 import temp_log
 import threading
 
@@ -36,7 +46,8 @@ class MainApp(App):
 class MainWindow(FloatLayout):
     """Main Window class"""
     dataSource = StringProperty('/dev/ttyACM0')
-    lastTemperature = StringProperty('n/a')
+    lastTemperature = NumericProperty(-1000.)
+    lastTime = NumericProperty(-1.)
 
     def update_last_temperature(self, dt):
         global dataThreadDataQueue
@@ -44,20 +55,48 @@ class MainWindow(FloatLayout):
         try:
             data = dataThreadDataQueue.get_nowait()
             if data is not None:
-                self.lastTemperature = str(data['data']['temperature'])
+                Logger.debug('Data: ' + str(data))
+                if 'data' in data and 'temperature' in data['data']:
+                    self.lastTemperature = float(data['data']['temperature'])
+                if 'time' in data:
+                    self.lastTime = float(data['time'])
         except Queue.Empty:
             pass
 
+
     def on_lastTemperature(self, instance, value):
         Logger.debug('lastTemperature has changed to: ' + str(value))
         children = self.children[:]
         while children:
             child = children.pop()
+            children.extend(child.children)
+            if child is self:
+                continue
             try:
                 child.on_lastTemperature(instance, value)
-            except Exception, e:
+                #Logger.debug('Called on_lastTemperature for child: ' + str(child))
+            except AttributeError:
                 pass
+            except Exception, e:
+                Logger.exception(str(e))
+
+
+    def on_lastTime(self, instance, value):
+        Logger.debug('lastTime has changed to: ' + str(value))
+        children = self.children[:]
+        while children:
+            child = children.pop()
             children.extend(child.children)
+            if child is self:
+                continue
+            #Logger.debug(str(child))
+            try:
+                child.on_lastTime(instance, value)
+                #Logger.debug('Called on_lastTime for child: ' + str(child))
+            except AttributeError, e:
+                pass
+            except Exception, e:
+                Logger.exception(str(e))
 
 
 class MyLabel(Label):
@@ -66,6 +105,65 @@ class MyLabel(Label):
         self.text = 'Current temperature: ' + str(value)
 
 
+class PlotWidget(Image):
+
+    def __init__(self, **kwargs):
+        super(Image, self).__init__(**kwargs)
+        self.data = numpy.array([], dtype=float);
+        self.lastTime = 0
+        self.lastTemperature = 0
+        self.figure = matplotlib.pyplot.figure()
+        self.plot_axes = self.figure.add_subplot(1, 1, 1)
+        self.plot_axes.hold(False)
+        self.plot_axes.set_ylabel('Temperature (deg C)')
+        self.plot_axes.set_xlabel('Time')
+        self.plot_axes.set_title('Recorded Temperature')
+
+
+    def update(self):
+        if not self.data.any():
+            return
+        #Logger.debug('self.data: ' + str(self.data))
+        #Logger.debug('self.data shape: ' + str(self.data.shape))
+        data = numpy.copy(self.data)
+        data = data.transpose()
+        #Logger.debug('transpoed data: ' + str(data))
+        #Logger.debug('transposed data shape: ' + str(data.shape))
+        t, temperature = numpy.split(data, 2, axis = 0)
+        #Logger.debug('time: ' + str(t[0]))
+        #Logger.debug('temperature: ' + str(temperature[0]))
+        self.plot_axes.plot(t[0], temperature[0])
+        image_data = StringIO.StringIO()
+        self.figure.savefig(image_data, format = 'png')
+        image_data.seek(0)
+        self.texture = ImageLoaderPygame(image_data, nocache = True).texture
+
+
+    def on_lastTemperature(self, instance, value):
+        self.lastTemperature = value
+        self.update_data()
+
+
+    def on_lastTime(self, instance, value):
+        self.lastTime = value
+        self.update_data()
+
+
+    def update_data(self):
+        if self.lastTime == 0 or self.lastTemperature == 0:
+            return
+        newpoint = numpy.array([(self.lastTime, self.lastTemperature)], dtype=float, ndmin = 2)
+        if not self.data.any():
+            self.data = newpoint
+            return
+        #Logger.debug('self.data: ' + str(self.data))
+        #Logger.debug('newpoint: ' + str(newpoint))
+        self.data = numpy.vstack((self.data, newpoint))
+        self.update()
+        #self.data = numpy.concatenate((self.data, newpoint), axis = 0)
+        #self.data = numpy.copy(self.data) # This will cause ObjectProperty to fire a change event
+
+
 if __name__ == '__main__':
     dataThread = threading.Thread(None, temp_log.threaded_reader, None, ['/dev/ttyACM0', dataThreadDataQueue, dataThreadCommandQueue])
     MainApp().run()