Python＆tkinter：canvas.lift和canvas.lower重叠按钮不起作用

Question

I created two overlapping buttons on a canvas, using tkinter and python 3.4:

Now I would like to bring button1 to the front (the button you cannot see right now, because it is under button2)

self.canvas.lift(self.button1)

But for some reason this does not work. Just nothing happens. Also lowering button2 has no effect. Can you tell me why?

import tkinter as tk

class Example(tk.Frame):
    def __init__(self, root):
        tk.Frame.__init__(self, root)
        self.canvas = tk.Canvas(self, width=400, height=400, background="bisque")
        self.canvas.create_text(50,10, anchor="nw", text="Click to lift button1")
        self.canvas.grid(row=0, column=0, sticky="nsew")
        self.canvas.bind("<ButtonPress-1>", self.click_on_canvas)

        self.button1 = tk.Button(self.canvas, text="button1")        
        self.button2 = tk.Button(self.canvas, text="button2")

        x = 40
        self.canvas.create_window(x, x, window=self.button1)
        self.canvas.create_window(x+5, x+5, window=self.button2)



    def click_on_canvas(self, event):

        print("lifting", self.button1)
        self.canvas.lift(self.button1)
        self.canvas.lower(self.button2)


if __name__ == "__main__":
    root = tk.Tk()
    Example(root).pack(fill="both", expand=True)
    root.mainloop()

Answer 1

Instead of calling lift() on the canvas, you need to call it on the widget instance directly:

def click_on_canvas(self, event):
    print("lifting", self.button1)
    self.button1.lift()
    self.button2.lower()   # Not necessary to both lift and lower

This is only true for widgets displayed via a window on your canvas.

If you were to draw objects such as lines or rectangles, you would use lift() or tag_raise() on the canvas instance as you were doing before.