KivyMD // Python如何创建一个加载对话框（弹出窗口），该对话框在后台运行代码的同时显示一个旋转的轮子

您的代码有几个问题。首先，当您使用构造时：

    with concurrent.futures.ThreadPoolExecutor() as executor:
        f1 = executor.submit(self.pop_up1())
        f2 = executor.submit(self.test())

有一个隐式executor.sutdown()调用，它等待提交的任务完成。请参阅文档。由于您在主线程上使用了此构造，因此所有GUI更新都将被阻止，直到所有提交的任务完成为止。因此，通常不应该在kivy应用程序的主线程上使用该构造。

第二个问题是an的创建和显示MDDialog应在主线程上完成，因此提交类似于pop_up1()the的方法executor可能会出现问题。

第三个问题是您尝试重复MDDialog使用if not self.dialog:条件。MDDialog无论如何，您都无法重用。

因此，考虑到所有这些，以下是您的代码的修改版本，可以满足我的要求：

from kivy.clock import Clock, mainthread
from kivy.lang import Builder
from kivy.uix.boxlayout import BoxLayout
from kivymd.app import MDApp
from kivymd.uix.dialog import MDDialog
import concurrent.futures

KV = '''
<Content>
    orientation: "vertical"
    spacing: -40
    
    MDSpinner:
        size_hint: None, None
        size: dp(46), dp(46)
        pos_hint: {'center_x': 0.1}
        active: True
    MDLabel:
        text: "Processing..."
        pos_hint: {'center_x': .7}

FloatLayout:

    MDFlatButton:
        text: "ALERT DIALOG"
        pos_hint: {'center_x': .5, 'center_y': .5}
        on_release: app.start()
'''


class Content(BoxLayout):
    pass

class Example(MDApp):
    dialog = None

    def build(self):
        return Builder.load_string(KV)

    def start(self):
        # this must be done on the main thread
        self.pop_up1()

        executor = concurrent.futures.ThreadPoolExecutor()
        # f1 = executor.submit(self.pop_up1)  # this must be done on the main thread
        f2 = executor.submit(self.test)


    def pop_up1(self):
        '''Displays a pop_up with a spinning wheel'''
        self.dialog = MDDialog(
            size_hint=(.45, None),
            auto_dismiss=True,
            type="custom",
            content_cls=Content(),
        )
        self.dialog.open()

    def test(self):
        '''Counts to 1000000 and then it closes pop_up1 and opens pop_up2'''
        for number in range(100000):
            print(number)
        self.dismiss()
        Clock.schedule_once( self.pop_up2)  # pop_up2() must be done on the main thread

    def pop_up2(self,*args):
        self.dialog = MDDialog(
            title="Done",
            size_hint=(.6, None),
            text="Done",
                )
        self.dialog.open()

    @mainthread
    def dismiss(self, *args):
        self.dialog.dismiss()


Example().run()