Python 3：无法同时使用串行通信和Tkinter按钮

Question

I am new to python. I am attempting to get serial input from an Arduino board and receive it in Python 3 on a Raspberry Pi 3. In the code below, I get the code just fine from the Arduino and I can display it using Tkinter. The thing is, depending on the code I get from the Arduino, I want to display different screens. For this, I have added a Tkinter button. This button should just call the NextButton subroutine and increment the DisplayScreen value. It should then recall the ShowDisplay routine and give me the next screen. The button does display on the screen, but clicking it does nothing.

Any help would be greatly appreciated. Thanks

import serial
from tkinter import *
v=" "
DisplayScreen =1
# Make Serial Connection
ser = serial.Serial('/dev/ttyACM0', 9600)
#Subroutine to increment display value
def NextButton():
    DisplayScreen = DisplayScreen +1
    Print ("Got Here")
    if DisplayScreen == 3:
        DisplayScreen = 1
    # Update Display
    ShowDisplay()

#Subroutine to show display
def ShowDisplay():
    # Make values available from other parts of the program.
    global v    
    if DisplayScreen == 1:
        # Get rid of existing display entities
        for widget in frame.winfo_children():
            widget.destroy()
        #Add Label
        Label(frame, text="Display Screen 1").grid(row=0, column=0)
        Label(frame, text=v).grid(row=1, column=0)  
        # Add button to go to next screen
        Button(frame, text='Next', command=NextButton).grid(row=3, column=1)
    else:
        # Get rid of existing display entities
        for widget in frame.winfo_children():
            widget.destroy()
        #Add Label
        Label(frame, text="Display Screen 2").grid(row=0, column=0)
        Label(frame, text=v).grid(row=1, column=0)  
        # Add button to go to next screen
        Button(frame, text='Next', command=NextButton).grid(row=3, column=1)


def update_label():
    global v
    # get arduino info
    PinballData= ser.readline()
    # convert data to text
    v = str(PinballData, 'utf-8')
    # show display
    ShowDisplay()
    root.after(10, update_label)
    #calls update_label function again after 1 second. (1000 milliseconds.)

root = Tk()
frame = Frame(root)
frame.grid()
update_label()
root.mainloop()

Answer 1

There are several things that need fixing:

• You should declare 'DisplayScreen' globally inside NextButton function.
• Print statement is wrong. It must be print()

Thus, the function NextButton has to look like:

def NextButton():
    global DisplayScreen
    DisplayScreen = DisplayScreen +1
    print("Got Here")
    if DisplayScreen == 3:
        DisplayScreen = 1
    # Update Display
    ShowDisplay()

By doing these changes, I have been able to display "Got Here" by clicking on the button. However, it is really complicated to click on it since you are updating the entire graphical interface each 10 ms.

I would strongly recommend to update only the label instead of the entire root. Even better, you can change the text of a widget at any time by associating a StringVar() :

v = StringVar()
Label(master, textvariable=v).pack()

In this way, you would have a much more stable graphical interface.

I would also recommend you to make use of classes since you have several variables shared between functions. Then, you could easily use self .