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update compass example
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‎docs/source/Screenshot_Kivy_Kompass.png‎

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‎docs/source/example_compass.rst‎

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.. code-block:: python
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from jnius import autoclass
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...
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class CompassApp(App):
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def __init__(self, **kwargs):
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"""
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Constructor of the Compass App
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1) The Java Android API DisplayMetrics is called to get
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information about the densityDpi factor of the Android device
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2) The Kivy Python-For-Android Android API is called to
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get access to the hardware sensors of the Android device
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"""
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super(CompassApp, self).__init__(**kwargs)
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DisplayMetrics = autoclass('android.util.DisplayMetrics')
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metrics = DisplayMetrics()
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metrics.setToDefaults()
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LoggerDisplayMetrics(metrics)
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self.densityDpi = metrics.densityDpi
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Hardware = autoclass('org.renpy.android.Hardware')
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self.hw = Hardware()
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Logger.info('COMPASS: Hardware Objects: %s'%(str(dir(self.hw))))
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Logger.info('COMPASS: Hardware Sensors\n%s\n'%(self.hw.getHardwareSensors()))
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def viewCompass(self, *largs):
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"""
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viewCompass calls the readSensor method of the
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magneticFieldSensor instance of the generic3AxisSensor, it reads the
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3-tuple value of the magnetic field
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the declination angle is computed as the angle of the magnetic field
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vector in the x,y-plane and the unity-vector of the y-axis.
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afterwards the rotateNeedle function rotates the needle as given
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by the declination angle parameter
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"""
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(x, y, z) = self.hw.magneticFieldSensor.readSensor()
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declination = Vector(x,y).angle((0,1))
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Logger.info('COMPASS: viewCompass x=%s y=%s z=%s declination=%s'%(x,y,z,declination))
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self.needle.rotateNeedle(declination)
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def stopApp(self,*largs):
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"""
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this function is called when pushed the stopButton, disables
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the magneticFieldSensor and stops the app
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"""
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self.hw.magneticFieldSensor.changeStatus(False)
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Logger.info('COMPASS: stop largs '+str(largs))
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self.stop()
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def build(self):
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"""
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Building all together:
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1) Creating the parent widget and clearing it to white background color
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2) Defining a suitable position and size of the CompassWidget, the
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needleSize and the stopButtonHeight depending on the densityDpi value
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given by DisplayMetrics
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3) Creating an instance of the CompassWidget and adding it to the
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parent widget and calling the appropriate build function
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4) Creating an instance of the NeedleWidget and adding it also to the
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parent widget and calling the appropriate build function
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5) Creating an instance of a Button widget and adding it as stopButton
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also to the parent widget and bind it with the stopApp function
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6) Calling the instance method changeStatus of the magneticFieldSensor
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instance with parameter True to enable the magnetic field sensor
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and additionally calling the function schedule_interval of the Clock
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class for a repeated call of the function viewCompass every second.
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"""
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parent = FloatLayout(size=(500,500))
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Window.clearcolor = (1, 1, 1, 1)
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if self.densityDpi == 240:
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CompassPos = Vector(50., 200.)
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CompassSize = Vector(400., 400.)
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needleSize = Vector(100., 60.)
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stopButtonHeight = 60
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elif self.densityDpi == 320:
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CompassPos = Vector(75., 300.)
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CompassSize = Vector(600., 600.)
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needleSize = Vector(150., 90.)
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stopButtonHeight = 90
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else:
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Logger.info('COMPASS: widget size should be adopted - minimum used for densityDpi=%s'%(str(self.densityDpi)))
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CompassPos = Vector(50., 200.)
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CompassSize = Vector(400., 400.)
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needleSize = Vector(100., 60.)
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stopButtonHeight = 60
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self.Compass = CompassWidget()
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parent.add_widget(self.Compass)
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self.Compass.build(pos=CompassPos,size=CompassSize)
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self.needle = NeedleWidget()
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parent.add_widget(self.needle)
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self.needle.build(center=CompassPos+CompassSize/2.,needleSize=needleSize)
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self.stopButton = Button(text='Stop', pos_hint={'right':1}, size_hint=(None,None), height=stopButtonHeight)
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parent.add_widget(self.stopButton)
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self.stopButton.bind(on_press=self.stopApp)
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self.hw.magneticFieldSensor.changeStatus(True)
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Clock.schedule_interval(self.viewCompass, 1.)
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return parent
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# ... imports
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Hardware = autoclass('org.renpy.android.Hardware')
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class CompassApp(App):
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needle_angle = NumericProperty(0)
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def build(self):
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self._anim = None
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Hardware.magneticFieldSensorEnable(True)
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Clock.schedule_interval(self.update_compass, 1 / 10.)
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def update_compass(self, *args):
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# read the magnetic sensor from the Hardware class
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(x, y, z) = Hardware.magneticFieldSensorReading()
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# calculate the angle
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needle_angle = Vector(x , y).angle((0, 1)) + 90.
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# animate the needle
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if self._anim:
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self._anim.stop(self)
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self._anim = Animation(needle_angle=needle_angle, d=.2, t='out_quad')
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self._anim.start(self)
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def on_pause(self):
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# when you are going on pause, don't forget to stop the sensor
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Hardware.magneticFieldSensorEnable(False)
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return True
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def on_resume(self):
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# reactivate the sensor when you are back to the app
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Hardware.magneticFieldSensorEnable(True)
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if __name__ == '__main__':
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CompassApp().run()
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If you compile this app, you will get an APK which outputs the following
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screen:

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