Question

我正在尝试编写一个Tkinter代码，如果按下名为“Rain”的按钮，那么看起来像雨的图像会开始移动。

我还不知道图像移动部分是如何工作的，但问题是当我点击“Rain”按钮时，它会写入 - ＆gt; “Rain”就像它应该但Canvas上没有图像。

另一个有趣的事情是，当我采取

这是我的代码：

 root = Tk()

#Create the canvas
canvas = Canvas(width=1000, height=1000)
canvas.pack()

#This is the part that does not work
#Nothing appears when this function is called 
def Rain():
    image3 = "Drops.png"
    drops = PhotoImage(file = image3)
    drops_background = canvas1.create_image(100, 100, image=drops)
    while True:
        canvas1.move(drops_background, 10, 10)
    print("Rain")

#Adding a button and making it to use function "Rain"
frame = Frame(root)
frame.pack()
button1 = Button(frame, text = "Rain", command = Rain, fg = "red" ).pack(side = LEFT)
root.mainloop()

另一件有趣的事情是，如果我把这个部分放在功能之外就开始工作了。

image3 = "Drops.png"
drops = PhotoImage(file = image3)
drops_background = canvas1.create_image(100, 100, image=drops)

如果有人能告诉我这里有什么问题，或者至少指出我正确的方向，这将帮助我很多。

Answer 1

PhotoImage（或更确切地说是PIL和Pillow模块）中存在问题 - 必须将PhotoImage分配给全局变量。如果将PhotoImage分配给局部变量，则Garbage Collector将其从内存中删除。

我的完整工作示例after

import Tkinter as tk
import random

# --- globals ---

drops_background = None
drops = None

# --- functions ---

def rain():
    global drops_background
    global drops

    filename = "Drops.png"

    drops = tk.PhotoImage(file=filename) # there is some error in PhotoImage - it have to be assigned to global variable

    drops_background = canvas.create_image(100, 100, image=drops)

    # move after 250ms
    root.after(250, move) # 250ms = 0.25s


def move():
    global drops_background

    # TODO: calculate new position
    x = random.randint(-10, 10)
    y = random.randint(-10, 10)

    # move object
    canvas.move(drops_background, x, y)

    # repeat move after 250ms
    root.after(250, move) # 250ms = 0.25s

# --- main ----

root = tk.Tk()

#Create the canvas
canvas = tk.Canvas(root, width=1000, height=1000)
canvas.pack()

#This is the part that does not work
#Nothing appears when this function is called 
#Adding a button and making it to use function "Rain"
frame = tk.Frame(root)
frame.pack()

button1 = tk.Button(frame, text="Rain", command=rain, fg="red" )
button1.pack(side=tk.LEFT)

root.mainloop()

after在给定时间后将功能和时间添加到其列表中并从此列表中运行mainloop运行函数。

after期望函数名称不包含()

Python Tkinter在buttonpress上移动图像

1 个答案: