Kivy - 在屏幕关闭后，后台应用程序无法正常工作

Question

我为Android设备创建了一个应用程序，以便尽快读取传感器数据（加速度计，指南针和陀螺仪）。

然而，它已经作为一个后台应用程序工作，以便我可以离开应用程序，它仍然读取传感器。当屏幕关闭时（通过时间或手动），应用程序将停止保存读取传感器数据。

如果你能以任何方式帮助我，我会非常感激。

这是我的代码 - ＆gt; main.py：

from kivy.app import App
from kivy.lang import Builder    
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.popup import Popup
from kivy.uix.label import Label
from kivy.uix.button import Button

from android import AndroidService

import atexit

kv = '''
BoxLayout:
    canvas.before:
        Color:
            rgba: 1, 1, 1, 1
        Rectangle:           
            pos: self.pos
            size: self.size
            source: 'Pictures/background_3.jpeg'
    orientation: 'vertical' 

    Label:  
        id: time_label          

    Label:
        id: label
        font_size: self.width/24
        text: ' '

    BoxLayout:
        orientation: 'vertical'
#        spacing: '30dp'
        Button:
            font_size: self.height/2
            id: toggle_button
            text: 'Start'
            on_press: app.start_measuring() 
            background_color: (0.1,0.2,0.79,1)       
        Button:
            font_size: self.height/2
            id: toggle_button
            text: 'Stop'
            on_press: app.stop_measuring() 
            background_color: (0.1,0.2,0.79,1)     
        Button:
            id: clear_button
            font_size: self.height/2
            text: 'Delete Data'
            on_press: app.ask_for_deletion()
            background_color: (0.8,0.1,0.1,1)            
'''

def exit_handler():
    if not out_file.closed:
        out_file.close()  

class AirApp(App):
    def build(self): 
        self.service = None                  
        self.root = Builder.load_string(kv)
        return self.root

    def start_measuring(self):                    
        self.root.ids.label.text = "Measuring ..." 
        service = AndroidService('AirApp', 'measuring')
        service.start('service started')
        self.service = service                      

    def stop_measuring(self):        
        self.root.ids.label.text = "Measurement stopped"
        if self.service: 
            self.service.stop()
            self.service = None

    def do_deletion(self,event):          #deletes file
        self.root.ids.label.text = "Measured data deleted"
        self.popup.dismiss()
        if self.service: 
            self.service.stop()
            self.service = None
        out_file = open("/sdcard/sensor_data.txt", "r+")
        out_file.truncate()
        out_file.close()       

    def ask_for_deletion(self):          #popup asking for intention 
        box = BoxLayout(orientation='vertical')
        content_cancel = Button(text='No', font_size = self.root.width/18)
        content_accept = Button(text='Yes', font_size = self.root.width/18)
        box.add_widget(Label(text='Are you sure that you want\nto delete all data irrevocably?', font_size = self.root.width/18))
        box.add_widget(content_cancel)
        box.add_widget(content_accept)
        self.popup = Popup(title='Delete data?', title_size = self.root.width/14, 
                      size_hint=(None, None), size=(self.root.width*3/4, self.root.height*6/7),
                      content=box)                     
        content_cancel.bind(on_release=self.popup.dismiss)
        content_accept.bind(on_release=self.do_deletion)                       
        self.popup.open()

    def on_pause(self):
        return True

    def on_resume(self):
        pass      

if __name__ == '__main__':    
    out_file = open("/sdcard/sensor_data.txt","a")
    out_file.close()
    atexit.register(exit_handler)       #if app gets forced to close: close file 
    AirApp().run()

这里的服务文件夹是另一个（后台脚本）main.py：

from plyer import accelerometer
from plyer import compass
from plyer import gyroscope
from plyer import gps

import atexit
import time

def exit_handler():
    accelerometer.disable()
    compass.disable()
    gyroscope.disable() 
    try:
        gps.stop()
    except NotImplementedError:
        import traceback
        traceback.print_exc()

def measure():
    out_file = open("/sdcard/sensor_data.txt","a")
    val_acceleration = accelerometer.acceleration
    val_compass = compass.orientation
    val_gyroscope = gyroscope.orientation
    try:
        safe_string = "Ax " + str(val_acceleration[0]) + "\n" + "Ay " + str(val_acceleration[1]) + "\n" + "Az " + str(val_acceleration[2]) + "\n"            
    except:
        safe_string = 'Ax 0.0\nAy 0.0\nAz 0.0\n'        
    out_file.write(safe_string)        

    try:
        safe_string = "Cx " + str(val_compass[0]) + "\n" + "Cy " + str(val_compass[1]) + "\n" + "Cz " + str(val_compass[2]) + "\n"            
    except:
        safe_string = 'Cx 0.0\nCy 0.0\nCz 0.0\n'
    out_file.write(safe_string)

    try:
        safe_string = "Gyx " + str(val_gyroscope[0]) + "\n" + "Gyy " + str(val_gyroscope[1]) + "\n" + "Gyz " + str(val_gyroscope[2]) + "\n"            
    except:
        safe_string = 'Gyx 0.0\nGyy 0.0\nGyz 0.0\n'            
    out_file.write(safe_string)    
    out_file.write("T1 " + str(long(time.time()*10**6)) + 'e-6\n\n')    # in seconds; for evaluation: *10**(-6)
    out_file.close()

if __name__ == '__main__':   
    accelerometer.enable()
    compass.enable()
    gyroscope.enable()  
    atexit.register(exit_handler)       #if app gets forced to close: close file  
    while True:
        measure()    

    accelerometer.disable()
    compass.disable()
    gyroscope.disable()