Clock.schedule_once 不更新标签，但正在调用更新方法

Question

我有一个标签，一旦我从服务器接收到文本，我需要在其中更新文本。方法正在运行，正在获取输出并且函数也被调用，但标签文本没有更新。

我的代码：

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on Mon Jan 21 00:34:58 2019

@author: driftking9987
"""
from kivy.app import App
from kivy.uix.togglebutton import ToggleButton
from kivy.uix.widget import Widget
from kivy.uix.boxlayout import BoxLayout
import requests
from kivy.properties import StringProperty
from kivy.clock import Clock
import time

url = 'http://119.........'
l_server_text = "abc..."
l_server_text_waiting = "def..."
l_server_text_error = "ghi..."
self_global = ""

class HBoxWidget(BoxLayout):

    def __init__(self, **kwargs):
        super(HBoxWidget, self).__init__(**kwargs)

class VBoxWidget_Details(BoxLayout):
    label_name = StringProperty()

    def __init__(self, **kwargs):
        super(VBoxWidget_Details, self).__init__(**kwargs)
        self.label_name = l_server_text


    def updateText(self, *args):
        print("string to be updated is : ")
        print(l_server_text)
        print("updated")
        self.label_name = l_server_text


class ContainerBox(BoxLayout):
    def __init__(self, **kwargs):
        super(ContainerBox, self).__init__(**kwargs)

class WipApp(App):
    def build(self):
        global self_global
        self_global = self
        Clock.schedule_once(lambda dt: retrieveDataFromServer(self_global,12), 2)
        return ContainerBox() 


def retrieveDataFromServer(self,id):
    global l_server_text
    l_server_text = l_server_text_waiting
    print(l_server_text)
    a = VBoxWidget_Details()
    a.updateText(self)
    try:
        r_headers = {
        'Content-type': 'application/json',
        }
        data_post_req =  '{"id":'+str(id)+'}'
        print(data_post_req)
        response = requests.post('http://119....', headers=r_headers, data=data_post_req)
        res = response.json()
        output_text = res['Message']
        output_text = output_text.replace(':', '\n')
        print(output_text)
        l_server_text = output_text
        a = VBoxWidget_Details()
        a.updateText(self)
        print("done")
    except Exception as e:
        print("exception")
        l_server_text = l_server_text_error
        a = VBoxWidget_Details()
        a.updateText(self)


if __name__ == '__main__':
    wapp = WipApp()
    wapp.run()

KV 文件：

<HBoxWidget>:

    AnchorLayout:
        anchor_x: 'center'
        anchor_y: 'center'
        Image:
            source: '/Users/driftking9987/Desktop/fp.gif'
<VBoxWidget_Details>:
    BoxLayout:
        orientation: "horizontal"
        size: [1,.25]
        pos: root.pos
        Label:
            id: label_name
            text: root.label_name
            color: [0,84,80,19]
        Widget:

<ContainerBox>:
    orientation: 'vertical'
    Label:
        text: 'Label'
        size_hint_y: 0.1
    BoxLayout:
        id: four_horizontals
        orientation: 'horizontal'
        HBoxWidget:
        BoxLayout:
            orientation:'vertical'
            BoxLayout:
            BoxLayout:
                orientation:'vertical'
                VBoxWidget_Details:
            BoxLayout:

下面是终端的输出：

driftking9987$ python pp.py 
[INFO   ] [Logger      ] Record log in /Users/driftking9987/.kivy/logs/kivy_19-01-21_47.txt
[INFO   ] [Kivy        ] v1.10.1
[INFO   ] [Python      ] v3.6.8 |Anaconda custom (64-bit)| (default, Dec 29 2018, 19:04:46) 
[GCC 4.2.1 Compatible Clang 4.0.1 (tags/RELEASE_401/final)]
[INFO   ] [Factory     ] 194 symbols loaded
[INFO   ] [Image       ] Providers: img_tex, img_imageio, img_dds, img_sdl2, img_gif (img_pil, img_ffpyplayer ignored)
[INFO   ] [Text        ] Provider: sdl2
[INFO   ] [Window      ] Provider: sdl2
[INFO   ] [GL          ] Using the "OpenGL ES 2" graphics system
[INFO   ] [GL          ] Backend used <gl>
[INFO   ] [GL          ] OpenGL version <b'2.1 INTEL-12.4.7'>
[INFO   ] [GL          ] OpenGL vendor <b'Intel Inc.'>
[INFO   ] [GL          ] OpenGL renderer <b'Intel(R) Iris(TM) Graphics 650'>
[INFO   ] [GL          ] OpenGL parsed version: 2, 1
[INFO   ] [GL          ] Shading version <b'1.20'>
[INFO   ] [GL          ] Texture max size <16384>
[INFO   ] [GL          ] Texture max units <16>
[INFO   ] [Window      ] auto add sdl2 input provider
[INFO   ] [Window      ] virtual keyboard not allowed, single mode, not docked
[INFO   ] [GL          ] NPOT texture support is available
[INFO   ] [Base        ] Start application main loop
def...
string to be updated is : 
def...
updated
{"id":12}
KAM TRY
 logout
 Contac
string to be updated is : 
KAM TRY
 logout
 Contac
updated
done

在 Kivy 应用程序上，我看到的只是 abc 是标签文本。

我计划在满足某些条件后递归调用retrieveDataFromServer，这应该会更改文本但没有发生。

有什么想法吗？

******************************更新********************* *******

假设我只想引用带有 id 的标签，那我该怎么做呢？

<HBoxWidget>:

    AnchorLayout:
        anchor_x: 'center'
        anchor_y: 'center'
        Image:
            source: '/Users/driftking9987/Desktop/fp.gif'
<VBoxWidget_Details>:
    BoxLayout:
        orientation: "horizontal"
        size: [1,.25]
        pos: root.pos
        the_label_g_info: label_name
        Label:
            id: label_name
            text: root.label_name
            color: [0,84,80,19]
        Widget:

<ContainerBox>:
    orientation: 'vertical'
    title_name: title
    Label:
        id: title
        text: 'Label'
        size_hint_y: 0.1
    BoxLayout:
        box_name: box_id
        id: four_horizontals
        orientation: 'horizontal'
        HBoxWidget:
        BoxLayout:
            orientation:'vertical'
            BoxLayout:
            BoxLayout:
                id: box_id
                the_label_g_info: label_name
                orientation:'vertical'
                VBoxWidget_Details:
            BoxLayout:

在 updateText 方法中，如果我尝试写 self.the_label_g_info.text="drift" ，它会显示 AttributeError: 'wapp' object has no attribute 'the_label_g_info'

我的意思是，我如何引用标签？我从 2 天开始尝试，似乎没有什么可以解决这个问题。同时，VBoxWidget_Details 的__init__ 内部的self.label_name = str(l_server_text) 似乎在初始化时正确设置了文本。

Answer 1

在您的retrieveDataFromServer() 方法中，我看到了：

    a = VBoxWidget_Details()
    a.updateText(self)

在两个地方。此代码正在创建一个新的VBoxWidget_Details 实例并在该新实例上调用updateText()，而不是在您显示的那个实例上。您可能需要在某处保存对现有 VBoxWidget_Details 的引用，并在您的 retrieveDataFromServer() 方法中引用该实例。