解决Python CustomTkinter界面冻结：多线程实现流畅的用户体验

import tkinter
import customtkinter
from pytube import YouTube

def startdownload():
    try:
        ytLink = link.get()
        # 以下两行代码是耗时操作，直接在主线程执行
        ytObject = YouTube(ytLink, on_progress_callback=on_progress)
        video = ytObject.streams.get_lowest_resolution()

        title.configure(text=ytObject.title)
        video.download() # 耗时操作，阻塞主线程
        finishlabel.configure(text="Downloaded")
    except:
        finishlabel.configure(text="Invlaid")

# ... 其他GUI设置和主循环

import tkinter
import customtkinter
from pytube import YouTube
import threading # 导入threading模块

# 定义下载任务的实际逻辑
def download_video():
    try:
        ytLink = link.get()
        # 重置UI状态，例如清空之前的完成信息和进度条
        finishlabel.configure(text="")
        number.configure(text="0%")
        bar.set(0)

        ytObject = YouTube(ytLink, on_progress_callback=on_progress)
        video = ytObject.streams.get_lowest_resolution()

        title.configure(text=ytObject.title) # 更新视频标题

        video.download() # 在工作线程中执行下载
        finishlabel.configure(text="Downloaded")
    except Exception as e: # 捕获更具体的异常
        print(f"下载失败: {e}")
        finishlabel.configure(text="无效链接或下载失败")

# 按钮点击时调用的函数，负责启动一个新线程
def startdownload():
    # 创建一个新线程，目标函数是download_video
    down_thread = threading.Thread(target=download_video)
    # 将线程设置为守护线程。这意味着当主程序退出时，守护线程会自动终止。
    down_thread.daemon = True 
    # 启动线程，下载任务将在后台执行
    down_thread.start()

# 进度更新回调函数
def on_progress(stream, chunk, bytes_remaning):
    total_size = stream.filesize
    bytes_downloaded = total_size - bytes_remaning
    percentage_of_compeletion = bytes_downloaded / total_size * 100
    per = str(int(percentage_of_compeletion))
    number.configure(text=per + "%")
    # 虽然在工作线程中直接更新GUI在某些情况下可行，
    # 但更推荐的做法是使用app.after()或队列机制将GUI更新调度回主线程。
    # 对于简单的CustomTkinter/Tkinter应用，直接更新可能不会立即导致问题，
    # 但在复杂场景下，应避免从非主线程直接操作GUI组件。
    number.update() # 强制更新GUI，注意潜在的线程安全问题

    bar.set(float(percentage_of_compeletion) / 100)
    # bar.update() # CTkProgressBar的set方法通常会自动触发重绘，无需显式调用update

# CustomTkinter GUI设置
customtkinter.set_appearance_mode("dark")
customtkinter.set_default_color_theme("blue")

app = customtkinter.CTk()
app.geometry("720x480")
app.title("Youtube Downloader")

title = customtkinter.CTkLabel(app, text="Enter Video Link")
title.pack(padx=10, pady=10)

url_var = tkinter.StringVar()
link = customtkinter.CTkEntry(app, width=350, height=40, textvariable=url_var)
link.pack()

finishlabel = customtkinter.CTkLabel(app, text="")
finishlabel.pack()

number = customtkinter.CTkLabel(app, text="0%")
number.pack()

bar = customtkinter.CTkProgressBar(app, width=400)
bar.set(0)
bar.pack(padx=10, pady=10)

download = customtkinter.CTkButton(app, width=200, text="Download", command=startdownload)
download.pack(padx=10, pady=10)

app.mainloop()