Question

我想在单击按钮时更改画布上的文本标签。如果要单击“上”按钮，我想将标签增加10；如果要单击“下”按钮，我要减少10。

这是我的代码，但是我不知道接下来要做什么：

import tkinter as tk

class Sys(tk.Tk, object):
    def __init__(self):
        super(Sys, self).__init__()
        self.title('SYSTEM')
        self.geometry('{0}x{1}'.format(500, 500))   # dimentions
        self.consumtion = 300
        self._build_system() 

    def _build_system(self):
        self.canvas = tk.Canvas(self, bg='lightgreen',  height=500, width=500)   # dimentions
                 '''changeable value'''
        self.cons = self.canvas.create_text(250,250, text = str(self.consumtion))

        '''button'''
        self.but = tk.Button( text = "UP")
        self.but.bind("<Button-1>", lambda event: self.consumption + 10)
        self.but.place(relx=0.8, rely = 0.7, anchor = "center")
        self.but = tk.Button(text = "DOWN")
        self.but.bind("<Button-1>", lambda event: self.consumption - 10)
        self.but.place(relx=0.9, rely = 0.7, anchor = "center")

       # pack all
        self.canvas.pack()

sys=Sys()

Answer 1

您可以使用记录在案的画布itemconfigure方法来更改画布上任何对象的任何配置选项。

例如，您可以编写一个名为change_consumption的方法，该方法采用一个参数来更改值的大小，并且可以使用itemconfigure来更改画布上显示的内容：

def change_consumption(self, amount):
    self.consumption += amount
    self.canvas.itemconfigure(self.cons, text=self.consumption)

您将为“向上”按钮绑定到此功能；对于“下”，您将通过-10：

self.but.bind("<Button-1>", lambda event: self.change_consumption(10))

Answer 2

在调用变量self.consumtion时会出现拼写错误，但是当您尝试更改它时，变量self.consumption会出现拼写错误。

画布上的文本对象不能像普通标签那样工作，而可以像文本小部件那样工作，可以跟踪选择以及选择，删除和插入的方法。我创建了一个更改文本的函数，然后让按钮以所需的偏移量调用该函数：

import tkinter as tk

class Sys(tk.Tk, object):
    def __init__(self):
        super(Sys, self).__init__()
        self.title('SYSTEM')
        self.geometry('{0}x{1}'.format(500, 500))   # dimentions
        self.consumption = 300
        self._build_system() 

    def _build_system(self):
        self.canvas = tk.Canvas(self, bg='lightgreen',  height=500, width=500)   # dimentions
        '''changeable value'''
        self.cons = self.canvas.create_text(250,250, text = str(self.consumption))

        '''button'''
        self.but = tk.Button( text = "UP")
        # Call on function change_label with amount = 10
        self.but.bind("<Button-1>", lambda event: self.change_label(10))
        self.but.place(relx=0.8, rely = 0.7, anchor = "center")
        self.but = tk.Button(text = "DOWN")
        # Call on function change_label with amount = -10
        self.but.bind("<Button-1>", lambda event: self.change_label(-10))
        self.but.place(relx=0.9, rely = 0.7, anchor = "center")

       # pack all
        self.canvas.pack()

    def change_label(self, amount):
        # Adjust self.consumption with amount
        self.consumption += amount
        # Delete all chars in self.cons
        self.canvas.dchars(self.cons, 0, tk.END)
        # Insetr new text in self.cons
        self.canvas.insert(self.cons, 0, str(self.consumption)) 

sys = Sys()

看看Editing Canvas Text Items

tkinter在画布上的可变值

2 个答案: