from kivy.app import App
from kivy.uix.screenmanager import Screen,SlideTransition
from kivy.core.text import LabelBase
from kivy.uix.button import ButtonBehavior
from kivy.uix.image import Image
from kivy.clock import Clock
import time

LabelBase.register(
 name='SiyuanHeiti',
 fn_regular='./font/SourceHanSansCN-Normal.ttf'
)

# 图像按钮
class ImageButton(ButtonBehavior,Image):
 pass

# 秒表屏幕
class StopwatchScreen(Screen):
 pass

# 时钟屏幕
class ClockScreen(Screen):
 pass

创建一个名为MainApp()的类，这是程序的主类。我们把各种交互控制的方法写在这里面：

class MainApp(App):
 sw_started = False # 秒表启动状态
 sw_seconds = 0 # 当前秒表秒数

 def update(self,n):
 # 如果秒表已启动，更新当前秒数
 if self.sw_started:
  self.sw_seconds += n

 # 更新当前时间
 self.root.ids['clock_screen'].ids['time'].text = time.strftime("[b]%H[/b]:%M:%S")
 # 更新秒表
 m,s = divmod(self.sw_seconds,60) # 返回一个包含商和余数的元组
 self.root.ids['stopwatch_screen'].ids['stopwatch'].text = ("%02d: %02d.[size=40]%02d[/size]" % (int(m),int(s),int(s*100%100)))

 # 重写程序启动的事件
 def on_start(self):
 Clock.schedule_interval(self.update,0)

 # 开始/停止
 def start_stop(self):
 self.root.ids['stopwatch_screen'].ids['start_stop'].text = '启动' if self.sw_started else '停止'
 self.sw_started = not self.sw_started

 # 重置秒表
 def reset(self):
 if self.sw_started:
  self.root.ids['stopwatch_screen'].ids['start_stop'].text = '启动'
  self.sw_started = False
 self.sw_seconds = 0

 def go_forward(self):
 screen_manager = self.root.ids['screen_manager']
 screen_manager.transition = SlideTransition(direction="right")
 screen_manager.current = "stopwatch_screen"

 def go_back(self):
 screen_manager = self.root.ids['screen_manager']
 screen_manager.transition = SlideTransition(direction="left")
 screen_manager.current = "clock_screen"

if __name__ == '__main__':
 app = MainApp()
 app.run()