python canvas 拖拽和移动\事件

image.png

"""
draw elastic shapes on a canvas on drag, move on right click;
see canvasDraw_tags*.py for extensions with tags and animation
"""

from tkinter import *
trace = False

class CanvasEventsDemo:
def init(self, parent=None):
canvas = Canvas(width=300, height=300, bg='beige')
canvas.pack()
canvas.bind('', self.onStart) # click
canvas.bind('', self.onGrow) # and drag
canvas.bind('', self.onClear) # delete all
canvas.bind('', self.onMove) # move latest
self.canvas = canvas
self.drawn = None
self.kinds = [canvas.create_oval, canvas.create_rectangle]

def onStart(self, event):
    self.shape = self.kinds[0]
    self.kinds = self.kinds[1:] + self.kinds[:1]      # start dragout
    self.start = event
    self.drawn = None

def onGrow(self, event):                              # delete and redraw
    canvas = event.widget
    if self.drawn: canvas.delete(self.drawn)
    objectId = self.shape(self.start.x, self.start.y, event.x, event.y)
    if trace: print(objectId)
    self.drawn = objectId

def onClear(self, event):
    event.widget.delete('all')                        # use tag all

def onMove(self, event):
    if self.drawn:                                    # move to click spot
        if trace: print(self.drawn)
        canvas = event.widget
        diffX, diffY = (event.x - self.start.x), (event.y - self.start.y)
        canvas.move(self.drawn, diffX, diffY)
        self.start = event

if name == 'main':
CanvasEventsDemo()
mainloop()

---

bind events on both canvas and its items

from tkinter import *

def onCanvasClick(event):
print('Got canvas click', event.x, event.y, event.widget)

def onObjectClick(event):
print('Got object click', event.x, event.y, event.widget, end=' ')
print(event.widget.find_closest(event.x, event.y)) # find text object's ID

root = Tk()
canv = Canvas(root, width=100, height=100)
obj1 = canv.create_text(50, 30, text='Click me one')
obj2 = canv.create_text(50, 70, text='Click me two')

canv.bind('', onCanvasClick) # bind to whole canvas
canv.tag_bind(obj1, '', onObjectClick) # bind to drawn item
canv.tag_bind(obj2, '', onObjectClick) # a tag works here too
canv.pack()
root.mainloop()