Quoting Guilherme Polo <[EMAIL PROTECTED]>:
On Sun, Nov 16, 2008 at 3:47 PM, <[EMAIL PROTECTED]> wrote:
Hello everyone,
I am trying to create bindable shapes with Tkinter that are dragged when the
user drags with the mouse. Here is an example (some code edited out for
simplicity). This is all within an "App" class:
self.canvas=Canvas(self.display, bg='blue')
self.canvas.bind('<B1-Motion>', self.onDrag)
self.x=10
self.y=10
#Draw ball, set up screen layout
self.box1=self.drawBox(self.canvas)
self.canvas.pack()
def drawBox(self,master):
newbox=master.create_rectangle(self.x, self.y, self.x+70, self.y+70,
width=5, fill='red')
return newbox
def onDrag(self,event):
self.canvas.move(self.box1,event.x-self.x,event.y-self.y)
self.x=event.x
self.y=event.y
This works as written, but it is not good form because it can only be used
with box1. <B1-Motion> is bound to the canvas rather that the box, and
"self.box1" is explicitly stated in the onDrag method. Therefore, if I
wanted to create 10 boxes (or even 2) I would have to write a new onDrag
method for each one. Also, if I want the box to only drag when the user
clicks INSIDE the box, I would have to create a new "dimensions" list for
each new box, and then use an if statement to see if the mouse is inside the
box, etc. I actually tried doing this and it makes the program run extremely
slow with only one box, so I don't think this is a good solution. It seems
logical to bind <B1-Motion> to box1 rather than the canvas, and that way the
box will react only if the mouse is inside the box, and I could create
multiple boxes, each with its own binding to <B1-Motion>. When I try to do
this, though, using something like this:
newbox=master.create_rectangle(self.x, self.y, self.x+70, self.y+70,
width=5, fill='red')
newbox.bind('<B1-Motion>', self.onDrag)
it gives me an error saying that I can't bind this method to this instance.
Didn't you mean an AttributeError ? The id returned my
create_rectangle surely doesn't have a bind method.
How can I make this work?
That is why Canvas has a method called tag_bind, to bind an item in
the canvas:
master.tag_bind(newbox, '<B1-Motion>', self.on_drag)
Thanks!
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--
-- Guilherme H. Polo Goncalves
Thanks. Yes, you're right, the message is "AttributeError: App instance
has no attribute 'on_drag'" However, when I make this change I get no
response at all when the program is run. My drawBox function now looks
like this:
def drawBox(self,master):
newbox=master.create_rectangle(self.x, self.y, self.x+70,
self.y+70, width=5, fill='red')
master.tag_bind(newbox, '<B1-Motion>', self.onDrag)
and my onDrag function looks like this:
def onDrag(self,event):
self.canvas.move(self,event.x-self.x,event.y-self.y)
self.x=event.x
self.y=event.y
This looks like it should work: it passed newbox as self and the
coordinates as event to the onDrag function, but I get no response at
all.
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