Tkinter中.place()布局导致控件不显示的原理与解决方案

import tkinter as tk

def button1_pressed():
    text = "Button 1 was pressed"
    label_text.append(text)
    update_label()

def update_label():
    label.config(text="\n".join(label_text))
    canvas.config(scrollregion=canvas.bbox("all"))

root = tk.Tk()
root.title("Scrollable Label")

# 创建两个Frame，但未指定宽度和高度
frame1 = tk.Frame(root)
frame1.place(x=0, y=0, anchor='nw')

frame2 = tk.Frame(root)
frame2.place(x=300, y=0, anchor='nw')

button1 = tk.Button(frame1, text="Button 1", command=button1_pressed)
button1.place(x=100, y=75, anchor='center') # 按钮被放置在frame1中

canvas = tk.Canvas(frame2, width=200, height=150) # Canvas有尺寸，但其父容器frame2可能没有
scrollbar = tk.Scrollbar(frame2, command=canvas.yview)
canvas.config(yscrollcommand=scrollbar.set)

label_text = []
label = tk.Label(canvas, text="")
label.pack() # Label使用pack放置在canvas内部

canvas.create_window((0, 0), window=label, anchor='nw')
canvas.place(x=0, y=0, anchor='nw') # Canvas被放置在frame2中
scrollbar.place(x=200, y=0, anchor='ne', relheight=1) # Scrollbar被放置在frame2中

root.mainloop()

import tkinter as tk

def button1_pressed():
    text = "Button 1 was pressed"
    label_text.append(text)
    update_label()

def update_label():
    label.config(text="\n".join(label_text))
    # 每次更新内容后，重新配置canvas的滚动区域
    canvas.update_idletasks() # 确保label尺寸已更新
    canvas.config(scrollregion=canvas.bbox("all"))

root = tk.Tk()
root.title("Scrollable Label with .place()")
root.geometry("500x200") # 为主窗口设置一个初始大小

# 创建两个Frame，并显式指定宽度和高度
# 调试时，添加背景色有助于观察控件边界
frame1 = tk.Frame(root, width=150, height=180, bg="lightblue")
frame1.place(x=10, y=10, anchor='nw')

frame2 = tk.Frame(root, width=320, height=180, bg="lightgreen")
frame2.place(x=170, y=10, anchor='nw')

button1 = tk.Button(frame1, text="Button 1", command=button1_pressed)
# 按钮在frame1中居中放置，使用相对位置更灵活
button1.place(relx=0.5, rely=0.5, anchor='center')

# 创建一个可滚动标签在右侧frame中
# Canvas不再需要显式width/height，可以由relwidth/relheight决定
canvas = tk.Canvas(frame2, bg="white")
scrollbar = tk.Scrollbar(frame2, command=canvas.yview)
canvas.config(yscrollcommand=scrollbar.set)

label_text = []
# label需要设置justify='left'和anchor='nw'以确保文本正确对齐
label = tk.Label(canvas, text="", bg="white", anchor='nw', justify='left')
label.pack(fill='both', expand=True) # Label仍然使用pack填充canvas的滚动区域

canvas.create_window((0, 0), window=label, anchor='nw')

# 使用相对尺寸放置canvas和scrollbar在frame2中
# canvas占据frame2的90%宽度，scrollbar占据10%宽度
canvas.place(relx=0, rely=0, relwidth=0.9, relheight=1)
scrollbar.place(relx=0.9, rely=0, relwidth=0.1, relheight=1)

root.mainloop()