python - guizero Raspberry Pi：按钮 -> 命令序列问题

Question

要求：在 guizero App 上按下按钮应该首先设置一个文本值，然后执行一个函数（这里是一个简单的 time.sleep()；最初是一个子进程）；执行该功能后，应显示结果文本；

#!/usr/bin/python3
# -*- coding: utf-8 -*-

from guizero import App, PushButton, Text
import subprocess
import time

# Action you would like to perform
def counter0():
    global s0
    text0.value = int(text0.value) + 1  # works
    text1.value = s0                    # works

def counter1():
    global s0
    text1.value = s0       # display a status value - but does not (!)
    time.sleep(1)          # originally a subprocess is called here; works
    text1.value = "ready"  # only diplays this after a delay

s0="start something after pressing butt1"

app = App("Hello world", layout="grid")

text0 = Text(app, text="1", align="left", grid=[0,1])
text1 = Text(app, text=s0, align="left",grid=[0,8] )
butt1 = PushButton(app, text="Button", command=counter1, align="left", grid=[0,2])
text0.repeat(10000, counter0)  # Schedule call to counter() every 1000ms

app.display()

很可能我不理解 guizero 背后的想法。任何想法如何管理这些要求？

Answer 1

如果我正确理解您的问题，您的具体问题就在这里：

    text1.value = s0       # display a status value - but does not (!)

这不起作用，因为guizero框架正在同步执行函数：没有其他代码执行——包括更新显示的代码——直到函数返回。

如果你想：

• 在运行命令之前显示一条消息subprocess
• 运行一些命令
• 命令完成后显示一条消息

然后你需要重写你的逻辑，这样你的应用程序就不会等待`counter1 完成。异步运行代码的一种选择是在单独的线程中运行它。例如：

from guizero import App, PushButton, Text
import threading
import time


# Action you would like to perform
def counter0():
    global s0
    text0.value = int(text0.value) + 1  # works
    text1.value = s0                    # works


def run_command():
    time.sleep(1)          # originally a subprocess is called here; works
    text1.value = "ready"  # only diplays this after a delay


def counter1():
    global s0
    text1.value = "Running command..."
    threading.Thread(target=run_command).start()


s0 = "start something after pressing butt1"

app = App("Hello world", layout="grid")

text0 = Text(app, text="1", align="left", grid=[0, 1])
text1 = Text(app, text=s0, align="left", grid=[0, 8])
butt1 = PushButton(app, text="Button", command=counter1,
                   align="left", grid=[0, 2])
text0.repeat(10000, counter0)

app.display()

运行上面的代码会给你以下行为：