python - 使用鼠标移动 tkinter Canvas

Question

我想通过鼠标单击(按住)+ 鼠标移动来移动整个 tkinter Canvas。我尝试使用 canvas.move 但不幸的是它不起作用。

如何滚动整个 Canvas ？(不是移动 Canvas 的每个元素，而是滚动 Canvas 的显示区域)

import Tkinter as Tk

oldx = 0
oldy = 0

def oldxyset(event):
    global oldx, oldy
    oldx = event.x
    oldy = event.y

def callback(event):
    # How to move the whole canvas here?
    print oldx - event.x, oldy - event.y

root = Tk.Tk()

c = Tk.Canvas(root, width=400, height=400, bg='white')
o = c.create_oval(150, 10, 100, 60, fill='red')
c.pack()

c.bind("<ButtonPress-1>", oldxyset)
c.bind("<B1-Motion>", callback)

root.mainloop()

Answer 1

通过 scan_mark 和 scan_dragto 方法， Canvas 内置了对鼠标滚动的支持。前者会记住您单击鼠标的位置，而后者会将窗口滚动适当数量的像素。

注意:gain 属性告诉 scan_moveto 鼠标移动每个像素要移动多少像素。默认情况下它是 10，所以如果你想要光标和 Canvas 之间 1:1 的相关性，你需要将这个值设置为 1(如示例所示)。

这是一个例子:

import Tkinter as tk
import random

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.xsb = tk.Scrollbar(self, orient="horizontal", command=self.canvas.xview)
        self.ysb = tk.Scrollbar(self, orient="vertical", command=self.canvas.yview)
        self.canvas.configure(yscrollcommand=self.ysb.set, xscrollcommand=self.xsb.set)
        self.canvas.configure(scrollregion=(0,0,1000,1000))

        self.xsb.grid(row=1, column=0, sticky="ew")
        self.ysb.grid(row=0, column=1, sticky="ns")
        self.canvas.grid(row=0, column=0, sticky="nsew")
        self.grid_rowconfigure(0, weight=1)
        self.grid_columnconfigure(0, weight=1)

        for n in range(50):
            x0 = random.randint(0, 900)
            y0 = random.randint(50, 900)
            x1 = x0 + random.randint(50, 100)
            y1 = y0 + random.randint(50,100)
            color = ("red", "orange", "yellow", "green", "blue")[random.randint(0,4)]
            self.canvas.create_rectangle(x0,y0,x1,y1, outline="black", fill=color)
        self.canvas.create_text(50,10, anchor="nw", 
                                text="Click and drag to move the canvas")

        # This is what enables scrolling with the mouse:
        self.canvas.bind("<ButtonPress-1>", self.scroll_start)
        self.canvas.bind("<B1-Motion>", self.scroll_move)

    def scroll_start(self, event):
        self.canvas.scan_mark(event.x, event.y)

    def scroll_move(self, event):
        self.canvas.scan_dragto(event.x, event.y, gain=1)


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