如何获取TkInter GUI（不是shell提示符）来侦听来自/dev/stdin的输入

Question

我正在编写一个带有图形用户界面的Python程序，该图形用户界面监听正在呈现的射频识别令牌（使用模拟键盘输入的USB阅读器）。我有问题，键盘/射频识别输入只有在我启动脚本的终端有焦点时才会被监听和操作。

如果GUI被聚焦，所有的输入都会被忽略，但是当终端被聚焦时，它会正常工作，甚至会向GUI和shell发送更新。我尝试在GUI上绘制文本输入框，但没有成功。

我想知道这是否与它需要如何使用多线程、队列甚至进程有关——有人能帮我更好地理解它吗？

代码如下，提前感谢！

#!/usr/bin/env python3
import sys
import MySQLdb

try:
    # python 2
    import Tkinter as tk
    import ttk
except ImportError:
    # python 3
    import tkinter as tk
    from tkinter import ttk

from threading import Thread

class Fullscreen_Window:

def __init__(self):
    self.tk = tk.Tk()
    self.tk.title("Listening for RFID token...")
    self.frame = tk.Frame(self.tk)
    self.frame.pack()

    self.tk.attributes('-zoomed', True)
    self.state = False
    self.tk.bind("<F11>", self.toggle_fullscreen)
    self.tk.bind("<Escape>", self.end_fullscreen)
    self.tk.config(cursor="none")

    t = Thread(target=self.listen_rfid)
    t.daemon = True
    t.start()

def toggle_fullscreen(self, event=None):
    self.state = not self.state  # Just toggling the boolean
    self.tk.attributes("-fullscreen", self.state)
    return "break"

def end_fullscreen(self, event=None):
    self.state = False
    self.tk.attributes("-fullscreen", False)
    return "break"

def listen_rfid(self):
    dbHost = 'localhost'
    dbName = 'python'
    dbUser = 'python'
    dbPass = 'PASSWORD'

    dbConnection = MySQLdb.connect(host=dbHost, user=dbUser, passwd=dbPass, db=dbName)
    cur = dbConnection.cursor(MySQLdb.cursors.DictCursor)

    with open('/dev/stdin', 'r') as tty:
        while True:
            RFID_input = tty.readline().rstrip()
            cur.execute("SELECT * FROM access_list WHERE rfid_code = '%s'" % (RFID_input))

            if cur.rowcount != 1:
                print("ACCESS DENIED")
                ttk.Label(self.tk, text="ACCESS DENIED").pack()
            else:
                user_info = cur.fetchone()
                print("Welcome %s!!" % (user_info['name']))
                ttk.Label(self.tk, text="Welcome %s!!" % (user_info['name'])).pack()
    tty.close()


if __name__ == '__main__':
w = Fullscreen_Window()
w.tk.mainloop()

Answer 1

经过多次的挠头，我再次找到了这条线索，并重新正确地阅读了它，然后意识到它包含了我想要的答案，尽管需要我做一点工作。

我的listen\u rfid功能现在看起来像下面的代码。希望对遇到我问题的人有用！

关键是查看/dev/input/by id并找到您的设备，将有一个符号链接（至少在我的Raspbian安装中有）指向更优雅的东西，例如，在我的例子中，“/event0”-如下）。然后，您可以使用pythonevdev来读取它。

如果您没有python evdev，只需使用sudo pip install evdev

以下是工作代码：

def listen_rfid(self):
    dbHost = 'localhost'
    dbName = 'python'
    dbUser = 'python'
    dbPass = 'PASSWORD'

    dbConnection = MySQLdb.connect(host=dbHost, user=dbUser, passwd=dbPass, db=dbName) # ToDo: This needs some error handling for if MySQL has gone away, and reconnect.
    cur = dbConnection.cursor(MySQLdb.cursors.DictCursor)

    from evdev import InputDevice
    from select import select

    keys = "X^1234567890XXXXqwertzuiopXXXXasdfghjklXXXXXyxcvbnmXXXXXXXXXXXXXXXXXXXXXXX"
    dev = InputDevice('/dev/input/event0')
    rfid_presented = ""

    while True:
       r,w,x = select([dev], [], [])
       for event in dev.read():
            if event.type==1 and event.value==1:
                    if event.code==28:
                        #print("RFID: " + str(rfid_presented))

                        cur.execute("SELECT * FROM access_list WHERE rfid_code = '%s'" % (rfid_presented))

                        if cur.rowcount != 1:
                            #print("ACCESS DENIED")
                            ttk.Label(self.tk, text="ACCESS DENIED").pack()
                        else:
                            user_info = cur.fetchone()
                            #print("Welcome %s!!" % (user_info['name']))
                            ttk.Label(self.tk, text="Welcome %s!!" % (user_info['name'])).pack()

                        rfid_presented = ""
                    else:
                        rfid_presented += keys[ event.code ]