Kivy How can i create time counter with progressbar?

问题

I want to make time counter with progressbar.The bar should be filled as time progresses.

I've progresed with the logic in the codes below, but the code starts before the program opens.

The bar should be stuffed every second.At least that's what I think.

'''
def update_time(self):
    while self.ids.pb.value < 30:
        time.sleep(1)
        self.ids.pb.value+=1
'''

Related .kv file.

'''
<Question>:
    name:"questions"
    canvas.before:
        Rectangle:
            pos: self.pos
            size: self.size
            source: 'bg2.jpg'
    FloatLayout:

        Label:
            id:quest
            pos_hint: {"x":0.1,"y":0.62}
            size_hint: 0.7,0.5
            text:root.sendquest()
            color:1, 0, 0, 1

        ProgressBar:
            id : pb
            min :0
            max :30
            pos_hint: {'x': 0.1,"y":0.45}
            size_hint_x :0.8
            size_hint_y :0.03
            background_color:0.8, 0.1, 0.1, 0
        Button: #A
            id:A
            pos_hint: {"x":0.045,"y":0.376}
            size_hint: 0.91,0.055
            on_press:
                root.reset() if root.check_truth("A") else root.popup()
'''

There are functions that are not relevant to this subject in main.py file.

回答1:

Kivy Programming Guide » Events and Properties

In Kivy applications, you have to avoid long/infinite loops or sleeping.

Solution

The solution is to use either Triggered Events (e.g. create_trigger() function) or Schedule Interval (e.g. schedule_interval() function).

Snippets - schedule_interval()

from kivy.properties import ObjectProperty
from kivy.clock import Clock


class RootWidget(ProgressBar):
    tick = ObjectProperty(None)

    def __init__(self, **kwargs):
        super(RootWidget, self).__init__(**kwargs)
        self.max = 30
        self.tick = Clock.schedule_interval(lambda dt: self.update_time(), 1)

    def update_time(self):
        self.value += 1
        if self.value >= 30:
            self.tick.cancel()    # cancel event

Snippets - create_trigger()

from kivy.properties import ObjectProperty
from kivy.clock import Clock


class RootWidget(ProgressBar):
    tick = ObjectProperty(None)

    def __init__(self, **kwargs):
        super(RootWidget, self).__init__(**kwargs)
        self.max = 30
        self.tick = Clock.create_trigger(lambda dt: self.update_time(), 1)
        self.tick()

    def update_time(self):
        self.value += 1
        if self.value < 30:
            self.tick()
        else:
            self.tick.cancel()    # cancel event

来源：https://stackoverflow.com/questions/56990499/kivy-how-can-i-create-time-counter-with-progressbar