Kivy Crashes On Widget Clear

[Yowser MaGuil]

Traceback (most recent call last):

   File "newGui.py", line 497, in <module>

   File "/usr/lib/python3.3/site-packages/kivy/app.py", line 792, in run

   File "/usr/lib/python3.3/site-packages/kivy/base.py", line 481, in runTouchApp

     EventLoop.window.mainloop()

   File "/usr/lib/python3.3/site-packages/kivy/core/window/window_pygame.py", line 381, in mainloop

     self._mainloop()

   File "/usr/lib/python3.3/site-packages/kivy/core/window/window_pygame.py", line 287, in _mainloop

     EventLoop.idle()

   File "/usr/lib/python3.3/site-packages/kivy/base.py", line 330, in idle

     Clock.tick_draw()

   File "/usr/lib/python3.3/site-packages/kivy/clock.py", line 429, in tick_draw

     self._process_events_before_frame()

   File "/usr/lib/python3.3/site-packages/kivy/clock.py", line 562, in _process_events_before_frame

     if event.tick(self._last_tick) is False:

   File "/usr/lib/python3.3/site-packages/kivy/clock.py", line 309, in tick

     ret = callback(self._dt)

   File "/usr/lib/python3.3/site-packages/kivy/uix/textinput.py", line 1520, in _update_graphics

     self.canvas.clear()

 AttributeError: 'NoneType' object has no attribute 'clear'

Getting this error when I clear widgets to redraw them. I am not posting any of my code yet, because there is too much of it.

I can provide more info as needed. Does the above error code ring any bells?

Thanks!!

[ZenCODE]

It's a pretty generic error, indicating one of the TextInput's you are using does not have a canvas at this point, or it has been removed. So, even though it's only a little, please post your code :-)

Thanks

[Yowser MaGuil]

this seems to be the function causing the crash:

def filterMess(self, convoPerson):

winD = self.message_display_window

winD.clear_widgets()

global currentConversation

currentConversation = int(convoPerson)

recipient = convoPerson

self.send_button.bind(on_press= lambda widget: self.sendMessage(recipient))

global allMessLog

messageArrayAll = allMessLog

messageArray = []

for eachMess in messageArrayAll:

sender = int(eachMess[3])

recip = int(eachMess[4])

if sender == int(convoPerson) or (sender == int(currentUser) and recip == int(convoPerson)):

messageArray.append(eachMess)

i = 0

if len(messageArray) == 0:

self.message_display_window.add_widget(Button(text="Start a conversation", size_hint=(1,1), background_color=(0,0.2,0.5,1)))

self.message_display_window.height = 545

i = len(messageArray)-1

while i>= 0:

curMes = messageArray[i]

mesStr = len(str(curMes[2]))

if mesStr <= 74:

ht = 48

elif mesStr>74 and mesStr<=148:

ht = 68

elif mesStr>148 and mesStr<=222:

ht = 88

if int(curMes[3]) == int(currentUser):

r = 0

g = 0.3

b = 0.7

a = 0.75

theSender = ""

space = "\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t"

else:

r = 0

g = 0.5

b = 0.1

a = 0.75

theSender = "  from  "+str(curMes[1])

space = ""

winD.add_widget(TextInput(text="\""+str(curMes[2])+"\""+"\n"+space+str(curMes[0])+theSender, readonly="true", height=ht, size_hint=(1,None), background_color= (r,g,b,a), foreground_color= (1,1,1,1)))

i = i-1

return recipient

[ZenCODE]

Okay, to the error is thrown in the TextInput class, so it's probably your:

    winD.add_widget(TextInput(...))

line. Try simplifying it and see if it throws an error then.

    winD.add_widget(TextInput(text="Hello"))

If not, then great. Slowly add back each parameter until the error re-appears. It simplifying does not help, you probably need to investigate the "winD" class. What is it? ("print str(winD)"). Is it doing anything to the TextInput that could cause this?

ps. "readonly" is a boolean property, so the parameter should be "readonly=True".

Peace out

[Yowser MaGuil]

Ok. Apparently it was the height property being weird. I was setting the height of the text widget dynamically by getting the length of the string it contains and passing that as 'ht'.

 Because I am in the python side, seems that using self.text_size[1] as per this tutorial is not gonna work. 'Self' seems to be referring to the root object, and not to the label. No idea how to make the label(read-only text widget) refer to itself..

Anyways, thanks for the help on this. 

ZenCODE, you da BEST!

[ZenCODE]

Awww shucks, you're too kind....;-)

Yeah, that example using the magical Kivy kv file binding. But there is always a Python equivalent, it's just a tad more verbose. What you could do is just attach the "on_size" event to your own callback. Something like:

    def context_resized(self, label, *args):
        self.height = label.height
        print "Other params are ", str(args)

    my_scrollview.context_resized = content_resized
    label.bind(on_size=my_scrollview.context_resized)

after you've created it created it. You could do that to call any function, and the label itself would be the first parameter (apart from the "self") passed into the callback and adjust the height/size in that callback?

ps. That just an example. There are probably cleaner ways to do it, but that should at least work...

Cheers