python - 无法解释小部件打包和未打包时的行为差异

Question

我正在制作一个小应用程序来可视化声音，但控件的行为不一致。当我启用(打包)输入字段时，程序将按我的预期运行。但是，如果我将它们注释掉，情节就不再显示，我只能听到声音。真的很困惑这个......

(在 Ubuntu 18.04 上运行 python 3.7.4)

以下作品:

import threading
import numpy as np
import tkinter as tk
from tkinter import Label, Button, Entry, TOP, BOTH
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg
from matplotlib.figure import Figure
from matplotlib import pyplot as plt
from matplotlib.animation import FuncAnimation
import pyaudio

DEFAULT_FREQUENCY = 420  # frequency in Hz
DEFAULT_DURATION = 3.0   # length of sound stream in seconds
VOLUME = 0.1             # must < 1
INTERVAL = 100           # plot interval in millisecond
PACKAGE_LENGTH = 1024    # number of samples in sound package
FS = 2**12               # sampling frequency sound, normal is 44100


class SoundVisualiser:

    def __init__(self, root):
        self.root = root
        self.root.title("Sound Visualiser")

        label = tk.Label(self.root, text="Sound Visualiser")
        label.pack()

        self.fig, self.ax = plt.subplots(figsize=(5, 5))
        self.canvas = FigureCanvasTkAgg(self.fig, master=self.root)
        self.canvas.get_tk_widget().pack(side=TOP, fill=BOTH, expand=1)
        self.ax.set_xlim(1000 * PACKAGE_LENGTH / FS, 0)

        freq_label = tk.Label(self.root, text='Frequency')
        self.frequency_entry = Entry(self.root)
        self.frequency_entry.insert(0, DEFAULT_FREQUENCY)

        durat_label = tk.Label(self.root, text='Duration')
        self.duration_entry = Entry(self.root)
        self.duration_entry.insert(0, DEFAULT_DURATION)

        freq_label.pack(side='left')
        self.frequency_entry.pack(side='left')
        durat_label.pack(side='left')
        self.duration_entry.pack(side='left')

        self.quit_button = Button(
            self.root, text='Quit', command=self.quit)
        self.quit_button.pack(side='right')

        self.control_button = Button(
            self.root, text='Start')
        self.control_button.bind('<Button-1>', self.start_visualisation)
        self.control_button.pack(side='right')

        self.duration = DEFAULT_DURATION
        self.xdata = np.linspace(0, 1000 * PACKAGE_LENGTH / FS, PACKAGE_LENGTH)

        self.audio = pyaudio.PyAudio()

    def quit(self):
        self.audio.terminate()
        self.root.quit()

    def generate_sound_stream(self):
        self.sound_stream = (
            (0.5 * np.sin(2 * np.pi * 325 / FS *
                    np.arange(FS * self.duration))) +
            (0.1 * np.sin(2 * np.pi * 330 / FS *
                    np.arange(FS * self.duration))) +
            (0.5 * np.sin(2 * np.pi * 340 / FS *
                    np.arange(FS * self.duration))) + 0
        ).astype(np.float32)

        self.ax.set_ylim(1.1 * np.min(self.sound_stream), 1.1 * np.max(self.sound_stream))

    def callback(self, in_data, frame_count, time_info, status):
        out = self.sound_stream[:frame_count]
        self.out_plot = out[:]
        self.sound_stream = self.sound_stream[frame_count:]
        return (out*VOLUME, pyaudio.paContinue)

    def play_sound(self):
        stream = self.audio.open(format=pyaudio.paFloat32,
                                 channels=1,
                                 rate=FS,
                                 output=True,
                                 stream_callback=self.callback)

        stream.start_stream()
        while stream.is_active():
            pass

        stream.stop_stream()
        stream.close()

        self.visualisation = None
        self.control_button.config(text='Start')

    def update_frame(self, frame):
        samples = len(self.out_plot)
        if samples == PACKAGE_LENGTH:
            self.line.set_data(self.xdata, self.out_plot)

        else:
            xdata = np.linspace(0, 1000 * samples / FS, samples)
            self.line.set_data(xdata, self.out_plot)

        return self.line,

    def start_visualisation(self, event):
        self.duration = float(self.duration_entry.get())
        self.generate_sound_stream()

        self.line, = self.ax.plot([], [], lw=3)

        self.control_button.config(text='run')
        duration_range = np.arange(0, self.duration, INTERVAL / 1000)
        self.visualisation = FuncAnimation(self.fig,
                                           self.update_frame,
                                           frames=duration_range,
                                           interval=INTERVAL,
                                           repeat=False)

        # start audio in a seperate thread as otherwise audio and
        # plot will not be at the same time
        self.play_sound_thread = threading.Thread(target=self.play_sound)
        self.play_sound_thread.start()

def main():
    root = tk.Tk()
    sound_visualiser = SoundVisualiser(root)
    root.mainloop()

if __name__ == '__main__':
    main()

注释掉条目字段将停止显示绘图

    def __init__(self, root):
        self.root = root
        self.root.title("Sound Visualiser")

        label = tk.Label(self.root, text="Sound Visualiser")
        label.pack()

        self.fig, self.ax = plt.subplots(figsize=(5, 5))
        self.canvas = FigureCanvasTkAgg(self.fig, master=self.root)
        self.canvas.get_tk_widget().pack(side=TOP, fill=BOTH, expand=1)
        self.ax.set_xlim(1000 * PACKAGE_LENGTH / FS, 0)

        freq_label = tk.Label(self.root, text='Frequency')
        self.frequency_entry = Entry(self.root)
        self.frequency_entry.insert(0, DEFAULT_FREQUENCY)

        durat_label = tk.Label(self.root, text='Duration')
        self.duration_entry = Entry(self.root)
        self.duration_entry.insert(0, DEFAULT_DURATION)

        # freq_label.pack(side='left')
        # self.frequency_entry.pack(side='left')
        # durat_label.pack(side='left')
        # self.duration_entry.pack(side='left')

        self.quit_button = Button(
            self.root, text='Quit', command=self.quit)
        self.quit_button.pack(side='right')

        self.control_button = Button(
            self.root, text='Start')
        self.control_button.bind('<Button-1>', self.start_visualisation)
        self.control_button.pack(side='right')

        self.duration = DEFAULT_DURATION
        self.xdata = np.linspace(0, 1000 * PACKAGE_LENGTH / FS, PACKAGE_LENGTH)

        self.audio = pyaudio.PyAudio()

正常输出有声音

Answer 1

我通过添加解决了这个问题

self.root.after(5, self.fig.canvas.draw)

作为函数中的最后一行def start_visualization(self, event)

我添加了一点延迟，因此线程 play_sound 有时间创建其第一个“out_plot”包。

另请参阅how-to-update-a-plot-on-tkinter-canvas?