通过 SSH 在 RPI 中使用 Tkinter 会引发 ImportError: Cannot load backend 'TkAgg'

Question

After reading many posts here, I still didn't find a solution to my problem.

I'm using Raspberrypi and connecting to it via SSH. I'm trying to run python script which has Tkinter's functionality.

I've tried using the following two approaches from the previous discussions on this error w/o success:

#1 Approach: export MPLBACKEND=TKAgg before calling the script.

#2 Approach: using the following commands in the appropriate order:

import matplotlib

matplotlib.use("TkAgg")
import matplotlib.pyplot as plt

Any ideas how to solve this?

Error:

import matplotlib.pyplot as plt
  File "/home/pi/imu_project/venv/lib/python3.7/site-packages/matplotlib/pyplot.py", line 2500, in <module>
    switch_backend(rcParams["backend"])
  File "/home/pi/imu_project/venv/lib/python3.7/site-packages/matplotlib/pyplot.py", line 288, in switch_backend
    newbackend, required_framework, current_framework))
ImportError: Cannot load backend 'TkAgg' which requires the 'tk' interactive framework, as 'headless' is currently running

I've also added the script:

# -*- coding: utf-8 -*-
from tkinter import *
from tkinter import ttk
import csv
import datetime
from mpu6050 import mpu6050

import matplotlib

matplotlib.use("TkAgg")
import matplotlib.pyplot as plt


class PlotRecAccGyro():
    def __init__(self, parent):
        self.parent = parent
        self.parent.title('MPU6050 - Acceleration and Gyroscope')
        self.frame = Frame(self.parent)
        self.frame.pack(fill=BOTH, expand=1)
        self.parent.resizable(width=False, height=False)
        self.plot_trigger = True
        self.record_trigger = False

        self.var_all = IntVar()
        self.var_plot = IntVar()
        self.var_rec = IntVar()
        self.accgyro_chkbtn_state = []
        self.chkbtn_list = []

        # Call MPU6050 class
        self.mpu = mpu6050(0x68)

        # LabelFrame - Select components
        self.labelframe_comp = LabelFrame(self.frame, text='Select components')
        self.labelframe_comp.grid(row=0, column=0, columnspan=3, sticky=N + E + W + S)
        self.labelframe_comp.grid_configure(padx=5, pady=5)

        # LabelFrame - Options to plot and record
        self.labelframe_opt = LabelFrame(self.frame, text='Options - Plot and Record')
        self.labelframe_opt.grid(row=0, column=3, columnspan=3, sticky=N + E + W + S)
        self.labelframe_opt.grid_configure(padx=5, pady=5)

        # Checkbuttons - Acceleration
        for i, j in enumerate(['Acc_x', 'Acc_y', 'Acc_z']):
            self.var_acc = IntVar()
            self.acc_chkbtn = Checkbutton(self.labelframe_comp, text=j, variable=self.var_acc,
                                          command=self.components_chk_func, padx=5, pady=5)
            self.acc_chkbtn.grid(row=i, column=0)
            self.accgyro_chkbtn_state.append(self.var_acc)
            self.chkbtn_list.append(self.acc_chkbtn)

        # Checkbuttons - Gyroscope
        for i, j in enumerate(['Gyro_x', 'Gyro_y', 'Gyro_z']):
            self.var_gyro = IntVar()
            self.gyro_chkbtn = Checkbutton(self.labelframe_comp, text=j, variable=self.var_gyro,
                                           command=self.components_chk_func, padx=5, pady=5)
            self.gyro_chkbtn.grid(row=i, column=1)
            self.accgyro_chkbtn_state.append(self.var_gyro)
            self.chkbtn_list.append(self.gyro_chkbtn)

        # Checkbutton - All
        self.all_chkbtn = Checkbutton(self.labelframe_comp, text='All', variable=self.var_all,
                                      command=self.all_chk_func, padx=5, pady=5)
        self.all_chkbtn.grid(row=1, column=2)

        # Button - Plot
        self.plot_chkbtn = ttk.Button(self.labelframe_opt, text='Start Plotting',
                                      command=lambda: self.plot_start_stop('plt_btn'))
        self.plot_chkbtn.grid(row=0, column=0, sticky=N + E + W + S, padx=5, pady=10)
        self.plot_chkbtn.configure(state='disabled')

        # Button - Record to a file
        self.rec_chkbtn = ttk.Button(self.labelframe_opt, text='Start Recording',
                                     command=lambda: self.record_start_stop('rec_btn'))
        self.rec_chkbtn.grid(row=1, column=0, sticky=N + E + W + S, padx=5, pady=10)
        self.rec_chkbtn.configure(state='disabled')

        # Label - File name
        self.rec_text = Label(self.labelframe_opt, text='to file (.csv)')
        self.rec_text.grid(row=1, column=1, sticky=N + E + W + S)

        # Entry - File name (Default name: SensorDataFile)
        self.file_name = ttk.Entry(self.labelframe_opt)
        self.file_name.insert(0, 'SensorDataFile')
        self.file_name.grid(row=1, column=2, sticky=N + E + W + S, padx=5, pady=10)
        self.file_name.configure(state='disabled')

    # Function called on clicking on 'All' checkbutton
    def all_chk_func(self):
        if [i.get() for i in self.accgyro_chkbtn_state] != ([1] * 6):
            [i.set(1) for i in self.accgyro_chkbtn_state]
            self.plot_chkbtn.configure(state='normal')
        else:
            [i.set(0) for i in self.accgyro_chkbtn_state]
            self.plot_chkbtn.configure(state='disabled')

    # Function called on clicking on 'Record' checkbutton
    def rec_chk_func(self):
        if self.var_rec.get() == 1:
            self.file_name.configure(state='normal')
        else:
            self.file_name.configure(state='disabled')

    # Function called on clicking on acceleration or gyroscope checkbuttons
    def components_chk_func(self):
        if (0 in [i.get() for i in self.accgyro_chkbtn_state]):
            self.var_all.set(0)
        else:
            self.var_all.set(1)
        if (1 in [i.get() for i in self.accgyro_chkbtn_state]):
            self.plot_chkbtn.configure(state='normal')
        else:
            self.plot_chkbtn.configure(state='disabled')

    # Function called on clicking on 'Start plotting' or 'Stop plotting' button
    def plot_start_stop(self, btn_name):
        if self.plot_chkbtn['text'] == 'Start Plotting':
            self.plot_chkbtn['text'] = 'Stop Plotting'
            self.rec_chkbtn.configure(state='normal')
            self.file_name.configure(state='normal')
            self.all_chkbtn.configure(state='disabled')
            for i in self.chkbtn_list:
                i.configure(state='disabled')
            self.plot_trigger = True
            self.record_trigger = False

            n_plots = [i.get() for i in self.accgyro_chkbtn_state]
            acc_n_plots = n_plots[0:3]
            gyro_n_plots = n_plots[3:6]

            time_values = [i for i in range(50, 0, -1)]
            acc_values = [[0] * 50, [0] * 50, [0] * 50]
            gyro_values = [[0] * 50, [0] * 50, [0] * 50]

            plt.ion()
            acc_legends = ['Acc_x', 'Acc_y', 'Acc_z']
            gyro_legends = ['Gyro_x', 'Gyro_y', 'Gyro_z']
            if (1 in acc_n_plots) and (1 in gyro_n_plots):
                fig, ax = plt.subplots(2, 1, figsize=(10, 7))
                ax[0].set_xlim(50, 0)
                ax[1].set_xlim(50, 0)
                ax[0].set_ylim([-30, 30])
                ax[1].set_ylim([-300, 300])
                for i, (title, y_axis_label) in enumerate(
                        [('Acceleration', 'Acceleration [m/s^2]'), ('Gyroscope', 'Angular velocity [deg/s]')]):
                    ax[i].set_title(title)
                    ax[i].set_ylabel(y_axis_label)
                    ax[i].set_xlabel('Latest 50 readings')
                    ax[i].grid()
                acc_plot_list = [ax[0].plot(time_values, acc_values[0], label=acc_legends[i])[0] if j == 1 else 0 for
                                 i, j in enumerate(acc_n_plots)]
                gyro_plot_list = [ax[1].plot(time_values, gyro_values[0], label=gyro_legends[i])[0] if j == 1 else 0 for
                                  i, j in enumerate(gyro_n_plots)]
                ax[0].legend(loc='upper left', fancybox=True, shadow=True)
                ax[1].legend(loc='upper left', fancybox=True, shadow=True)
            else:
                fig, ax = plt.subplots(1, 1, figsize=(10, 4))
                ax.set_xlim(50, 0)
                if 1 in acc_n_plots:
                    acc_plot_list = [ax.plot(time_values, acc_values[0], label=acc_legends[i])[0] if j == 1 else 0 for
                                     i, j in enumerate(acc_n_plots)]
                    ax.set_title('Acceleration')
                    ax.set_xlabel('Latest 50 readings')
                    ax.set_ylabel('Acceleration [m/s^2]')
                    ax.set_ylim([-30, 30])
                    ax.grid()
                else:
                    gyro_plot_list = [ax.plot(time_values, gyro_values[0], label=gyro_legends[i])[0] if j == 1 else 0
                                      for i, j in enumerate(gyro_n_plots)]
                    ax.set_title('Gyroscope')
                    ax.set_xlabel('Latest 50 readings')
                    ax.set_ylabel('Angular velocity [deg/s]')
                    ax.set_ylim([-300, 300])
                    ax.grid()
                ax.legend(loc='upper left', fancybox=True, shadow=True)
            plt.tight_layout()

            while self.plot_trigger:
                current_time = datetime.datetime.now()
                accel_data = self.mpu.get_accel_data()
                gyro_data = self.mpu.get_gyro_data()
                current_acc = [accel_data['x'], accel_data['y'], accel_data['z']]
                current_gyro = [gyro_data['x'], gyro_data['y'], gyro_data['z']]

                for i, j in enumerate(acc_n_plots):
                    if j == 1:
                        acc_values[i].append(current_acc[i])
                        del acc_values[i][0]
                        acc_plot_list[i].set_ydata(acc_values[i])
                for i, j in enumerate(gyro_n_plots):
                    if j == 1:
                        gyro_values[i].append(current_gyro[i])
                        del gyro_values[i][0]
                        gyro_plot_list[i].set_ydata(gyro_values[i])

                if self.record_trigger:
                    row = [current_time.strftime('%Y-%m-%d'), current_time.strftime('%H:%M:%S'),
                           current_time.strftime('%f')]
                    row = row + [i for i, j in
                                 zip(current_acc + current_gyro, [i.get() for i in self.accgyro_chkbtn_state]) if
                                 j == 1]
                    self.row_to_write.writerow(row)
                plt.draw()
                plt.pause(0.0001)
            plt.close('all')

        elif self.plot_chkbtn['text'] == 'Stop Plotting':
            self.plot_chkbtn['text'] = 'Start Plotting'
            self.rec_chkbtn.configure(state='disabled')
            self.file_name.configure(state='disabled')
            self.all_chkbtn.configure(state='normal')
            for i in self.chkbtn_list:
                i.configure(state='normal')
            self.plot_trigger = False
            self.record_trigger = False

    # Function called on clicking on 'Start writing' or 'Stop writing' button
    def record_start_stop(self, btn_name):
        if self.rec_chkbtn['text'] == 'Start Recording':
            self.rec_chkbtn['text'] = 'Stop Recording'
            self.plot_chkbtn.configure(state='disabled')
            self.file_name.configure(state='disabled')
            print('Started recording sensor data...')

            if self.file_name.get() != '':
                filename = self.file_name.get()
            else:
                filename = 'NoFileName'
            self.file_to_write = open(filename + '.csv', 'w')  # Open the file
            self.row_to_write = csv.writer(self.file_to_write, lineterminator='\n')
            column_titles = ['Date\n(YY:MM:DD)', 'Time\n(HH:MM:SS)', 'Time\n(µs)']
            column_titles = column_titles + [i for i, j in zip(
                ['Ax\n(m/s^2)', 'Ay\n(m/s^2)', 'Az\n(m/s^2)', 'Gx\n(deg/s)', 'Gy\n(deg/s)', 'Gz\n(deg/s)'],
                [i.get() for i in self.accgyro_chkbtn_state]) if j == 1]
            self.row_to_write.writerow(column_titles)
            self.record_trigger = True

        elif self.rec_chkbtn['text'] == 'Stop Recording':
            self.rec_chkbtn['text'] = 'Start Recording'
            self.plot_chkbtn.configure(state='normal')
            self.file_name.configure(state='normal')
            print('Stopped recording sensor data...')
            self.record_trigger = False
            self.file_to_write.close()


if __name__ == '__main__':
    root = Tk()
    plotrectool = PlotRecAccGyro(root)
    root.resizable(width=False, height=False)
    root.mainloop()

Answer 1

Solution:

To download and use MobaXterm .