用鼠標移動tkinter畫布

Question

我想用鼠標點擊（按住）+鼠標移動整個tkinter Canvas。我嘗試使用canvas.move，但它不起作用。

如何在整個畫布中滾動？（不移動畫布中的每個元素，而是滾動畫布的顯示區域）

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

畫布具有內置的用於與鼠標滾動支持經由scan_mark和scan_dragto方法。前者記得你點擊鼠標的位置，後者則會滾動窗口適當的像素。

注意：gain屬性告訴scan_moveto爲鼠標移動的每個像素移動多少個像素。默認情況下它是10，所以如果你想在光標和畫布之間建立1：1的相關性，你需要將這個值設置爲1（如示例所示）。

下面是一個例子：

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()