canvas 的两页链接在 python 中

Question

在我的 GUI 中我使用了 canvas 我希望我的程序链接到两页第一页来编写 'welcome' 然后按下一个按钮将它移动到程序页面.. 我尝试添加 Next 功能，但我迷路了

from tkinter import ttk

root = Tk()
root.geometry('400x400')
root.columnconfigure(0, weight=1)

MyImage = PhotoImage(file='222.png')
MyImage1 = PhotoImage(file='66.png')
#the welcome page
def Next():
    global myCanvas, myCanvas2
    myCanvas2.delete(all)
    myCanvas = Canvas(root, width=350, height=300, bd=0, highlightthickness=0).pack(fill='both', expand=True)
    myCanvas.create_image(0,0,image= MyImage, anchor='nw')
    #Button for location
    SaveLoc = Button(root, width=15, bg='#EDB491',fg='white', text='Choose location', command = openLocation)
    myCanvas.create_window(145,154, anchor='nw', window=SaveLoc)
    #Error message of locatino
    LocError = myCanvas.create_text(200,187, text='You must select a location',fill='#E1B5C6', font=('jost', 10))


#File location
Folder_Name =""
def openLocation():
    global Folder_Name
    Folder_Name = filedialog.askdirectory()
    if len(Folder_Name) > 1:
        myCanvas.itemconfig(LocError,text=Folder_Name, fill='green')
    else:
        myCanvas.itemconfig(LocError,text='Please Choose Folder!!',fill='red')


myCanvas2 = Canvas(root, width=350, height=300, bd=0, highlightthickness=0)
myCanvas2.pack(fill='both', expand=True)
CanvasImage=myCanvas2.create_image(0,0,image= MyImage1, anchor='nw')
#Download button
Down = Button(root, width=10, bg='#EDB491',fg='white', text='go', command= Next)
DownW=myCanvas2.create_window(162,300, anchor='nw', window=Down)

root.mainloop()

Answer 1

这个问题在 Whosebug 上出现了数百次。

你犯了最常见的错误

 variable = Widget.pack()

它将 None 分配给 variable 因为 pack()/grid()/place() returns None

你必须分两步完成

 variable = Widget
 variable.pack()

你有

 myCanvas = Canvas(...).pack(...)

所以它将 None 分配给 myCanvas 然后 myCanvas.create_image 意味着

 None.create_image(...)

然后出现错误

 AttributeError: 'NoneType' object has no attribute 'create_image'

你需要

 myCanvas = Canvas(...)
 myCanvas.pack(...)

编辑：

我的版本只有一个 Canvas 所以我不需要另一个 pack()

我做了其他更改 - 即。我使用 anchor="center" 将按钮和文本放在中间。

顺便说一句：PEP 8 -- Style Guidefor Python Code

import os
import tkinter as tk  # PEP8 `import *` is not preferred
from tkinter import ttk
from tkinter import filedialog

# --- functions --- (PEP8: lower_case_names) (PEP8: all functions before main part)

def next_image():
    # no need `global my_canvas` because I don't try to assign `=` to `my_canvas`
    global save_loc  # PEP8: `global` in separed lines
    global loc_error
    
    my_canvas.delete('all')
    
    my_canvas.create_image(0, 0, image=my_image_2, anchor='nw')
    
    #Button for location
    save_loc = tk.Button(root, width=15, bg='#EDB491', fg='white', text='Choose location', command=open_location)
    my_canvas.create_window(200, 200-20, anchor='center', window=save_loc)
    
    #Error message of locatino
    loc_error = my_canvas.create_text(200, 200+20, anchor='center', text='You must select a location', fill='#E1B5C6', font=('jost', 10))

def open_location():
    global folder_name    
    
    folder_name = filedialog.askdirectory()
    
    if folder_name:
        my_canvas.itemconfig(loc_error, text=folder_name, fill='green')
    else:
        my_canvas.itemconfig(loc_error, text='Please Choose Folder!!', fill='red')

# --- main --- (PEP8: lower_case_names)

# folder with running code - to create full path to images
APP_HOME = os.path.dirname(os.path.abspath(__file__))
print('APP_HOME:', APP_HOME)

# File location  # (PEP8: one space after `#`)
folder_name = ""

root = tk.Tk()
root.geometry('400x400')
#root.columnconfigure(0, weight=1) # don't need it if I don't use `grid()`

my_image_1 = tk.PhotoImage(file=os.path.join(APP_HOME, 'lenna.png'))
my_image_2 = tk.PhotoImage(file=os.path.join(APP_HOME, 'lenna.png'))
    
my_canvas = tk.Canvas(root, width=350, height=300, bd=0, highlightthickness=0)
my_canvas.pack(fill='both', expand=True)

canvas_image = my_canvas.create_image(0, 0, image=my_image_1, anchor='nw')

# Download button
down_button = tk.Button(root, width=10, bg='#EDB491', fg='white', text='GO', command=next_image)
my_canvas.create_window(200, 200, anchor='center', window=down_button)

root.mainloop()

我使用来自维基百科的图片：Lenna

lenna.png

canvas 的两页链接在 python 中

two pages of canvas linked in python

python

canvas

tkinter

root