Python Tkinter单选换背景及点击按钮移动文字功能实现问题求助

问题核心原因 #

你代码中self.lbl1 = Label(self.canvas, text = "Welcome").place(x = 100, y = 50)写法存在两处错误：

• Tkinter中所有组件布局方法（pack/grid/place）的返回值均为None，你直接链式调用后self.lbl1实际存储的是空值，后续canvas.move()方法无法找到目标元素
• Label是独立组件，放在Canvas上时不属于Canvas的原生绘制元素，Canvas.move()方法仅对Canvas自身创建的图形/文本对象生效

修正方案 #

把画布上的文本改用Canvas原生的create_text方法创建，修改两处代码即可：

1. 替换原Label创建代码：
   把self.lbl1 = Label(self.canvas, text = "Welcome").place(x = 100, y = 50)
   改为self.txt_id = self.canvas.create_text(100, 50, text="Welcome")
2. 修改左右移动方法的操作对象：
   把processbtLeft和processbtRight方法里的self.lbl1替换为self.txt_id，不需要额外调用canvas.update()，Tkinter事件循环会自动刷新界面。

修正后完整代码 #

from tkinter import * # Import tkinter

class Buttons:
    def __init__(self):
        window = Tk() # Create a window
        window.title("Radio Buttons and Buttons")
        frame1 = Frame(window) # Create and add a frame to window
        frame1.pack() 
        self.v1 = IntVar()
        rbRed = Radiobutton(frame1, text = "Red", variable = self.v1, value=1, command = self.processRb) 
        rbYellow = Radiobutton(frame1, text = "Yellow", variable = self.v1, value=2, command = self.processRb) 
        rbWhite = Radiobutton(frame1, text = "White", variable = self.v1, value=3, command = self.processRb) 
        rbGrey = Radiobutton(frame1, text = "Grey", variable = self.v1, value=4, command = self.processRb) 
        rbGreen = Radiobutton(frame1, text = "green", variable = self.v1, value=5, command = self.processRb) 

        rbRed.grid(row = 1, column = 1)
        rbYellow.grid(row = 1, column = 2)
        rbWhite.grid(row = 1, column = 3)
        rbGrey.grid(row = 1, column = 4)
        rbGreen.grid(row = 1, column = 5)

        frame2 = Frame(window, bg = "blue")
        frame2.pack() 
        self.canvas = Canvas(window)
        self.canvas.pack()

        # 改用Canvas原生方法创建文本，拿到元素ID
        self.txt_id = self.canvas.create_text(100, 50, text="Welcome")

        frame3 = Frame(window) # Create and add a frame to window
        frame3.pack() 
        btLeft = Button(frame3, text = "<=", command = self.processbtLeft)
        btRight = Button(frame3, text = "=>", command = self.processbtRight)
        btLeft.grid(row = 1, column = 1)
        btRight.grid(row = 1, column = 2)
        
        window.mainloop() # Create an event loop
    
    def processbtLeft(self):
        self.canvas.move(self.txt_id, -10, 0)  
    def processbtRight(self):
        self.canvas.move(self.txt_id, 10, 0)  

    def processRb(self):
        if self.v1.get() == 1:
            self.canvas["bg"] = "red"
        elif self.v1.get() == 2:
            self.canvas["bg"] = "yellow"
        elif self.v1.get() == 3:
            self.canvas["bg"] = "white"
        elif self.v1.get() == 4:
            self.canvas["bg"] = "grey"
        elif self.v1.get() == 5:
            self.canvas["bg"] = "green"
    
        
Buttons()

内容的提问来源于stack exchange，提问作者Amarillo