'Cannot add kivy.uix.actionbar.ActionSeparator - it already has a parent'

[DavidA2014]

Working with Kivy 1.9.1 on Windows 8.1, I get an exception with a certain widget tree when working with garden.matplotlib, which uses actionbar. I'm told that this is a generic Kivy issue, not an issue with garden.matplotlib.

Here are files that demo the problem. Sorry they are long but I did my best to cut them down.

main.py:

#!/usr/bin/python3

import sys
from kivy.app import App
from kivy.config import Config

Config.set('graphics', 'width', '800')
Config.set('graphics', 'height', '600')

from mygraph import CMplGraph

class GuiApp(App):

    def __init__(self, **kwargs):
        super(GuiApp, self).__init__(**kwargs)


if __name__ == '__main__':

    GuiApp().run()

mygraph.py

import matplotlib
matplotlib.use('module://kivy.garden.matplotlib.backend_kivy')
from matplotlib.figure import Figure
from numpy import arange, sin, pi
from kivy.app import App
import numpy as np
from kivy.garden.matplotlib.backend_kivyagg import FigureCanvas,\
                                                NavigationToolbar2Kivy
from matplotlib.transforms import Bbox
import matplotlib.pyplot as plt
from kivy.uix.boxlayout import BoxLayout

listA=[(0xBE14, 0x3408), (0xC65E, 0x3ABE)]

listB = [( 13322,  -16873), ( 15038,  -14751)]

def press(event):
    print('press released from test', event.x, event.y, event.button)


def release(event):
    print('release released from test', event.x, event.y, event.button)


def keypress(event):
    print('key down', event.key)


def keyup(event):
    print('key up', event.key)


def motionnotify(event):
    print('mouse move to ', event.x, event.y)


def resize(event):
    print('resize from mpl ', event)


def scroll(event):
    print('scroll event from mpl ', event.x, event.y, event.step)


def figure_enter(event):
    print('figure enter mpl')


def figure_leave(event):
    print('figure leaving mpl')


def close(event):
    print('closing figure')

def autolabel(rects):
    # attach some text labels
    for rect in rects:
        height = rect.get_height()
        ax.text(rect.get_x() + rect.get_width() / 2., 1.05 * height,
                '%d' % int(height), ha='center', va='bottom')

def callback(instance):
    autolabel(rects1)
    autolabel(rects2)
    canvas.draw()

class CMplGraph(BoxLayout):
    """This class presents an example graphical plot using MatPlotLib
    """
    pass

    def __init__(self, **kwargs):
        super(CMplGraph, self).__init__(**kwargs)
        self.create_plot()

    def create_plot(self):
        N = 5
        menMeans = (20, 35, 30, 35, 27)
        menStd = (2, 3, 4, 1, 2)

        ind = np.arange(N)  # the x locations for the groups
        width = 0.35       # the width of the bars

        fig, ax = plt.subplots()

        for i in range(len(listA)):
            x = listA[i][0]
            y = listA[i][1]
            if x > 32767:
                x = x - pow(2,16)
            if y > 32767:
                y = y - pow(2,16)
            x = x / pow(2,14)
            listA[i] = (i,x)

        xCoords = [ t[0] for t in listA ]
        yCoords = [ t[1] for t in listA ]

        lineA = ax.plot(xCoords, yCoords, color='blue', marker='o', markerfacecolor='blue', markersize=6)

        for i in range(len(listB)):
            x = listB[i][0]
            y = listB[i][1]
            if x > 32767:
                x = x - pow(2,16)
            if y > 32767:
                y = y - pow(2,16)
            x = x / pow(2,14)
            listB[i] = (i,x)

        xCoords = [ t[0] for t in listB ]
        yCoords = [ t[1] for t in listB ]

        lineB = ax.plot(xCoords, yCoords, color='red', marker='o', markerfacecolor='red', markersize=6)

        ax.set_xlabel('RB')
        ax.set_ylabel('Magnitude')
        ax.set_title('Data')
        ax.set_ylim([-2, 2])
        ax.legend((lineA[0], lineB[0]), ('Real', 'Imag'))

        fig.canvas.mpl_connect('button_press_event', press)
        fig.canvas.mpl_connect('button_release_event', release)
        fig.canvas.mpl_connect('key_press_event', keypress)
        fig.canvas.mpl_connect('key_release_event', keyup)
        fig.canvas.mpl_connect('motion_notify_event', motionnotify)
        fig.canvas.mpl_connect('resize_event', resize)
        fig.canvas.mpl_connect('scroll_event', scroll)
        fig.canvas.mpl_connect('figure_enter_event', figure_enter)
        fig.canvas.mpl_connect('figure_leave_event', figure_leave)
        fig.canvas.mpl_connect('close_event', close)

        canvas = fig.canvas

        nav1 = NavigationToolbar2Kivy(canvas)

        self.add_widget(nav1.actionbar)
        self.add_widget(canvas)

gui.kv

<CMplGraph>:
    id: my_graph
    orientation: 'vertical'

TabbedPanel:
    id: tab_panel
    do_default_tab: False

    TabbedPanelItem:
        id: tab_graph
        text: 'Graph'

        BoxLayout:
            id: CalBoxLayout
            orientation: 'horizontal'

            CMplGraph:

The problem

If I run the code as is, all is fine:

python main.py

If, in gui.kv, I replace the last line ( CMplGraph: ) with:

            BoxLayout:
                id: CalButtons
                orientation: 'vertical'
                size_hint_x: .25

                Button:
                    text: '1'

            BoxLayout:
                id: MyGraph

                CMplGraph:

I get an exception:

C:\>python main.py
 Traceback (most recent call last):
   File "main.py", line 20, in <module>
     GuiApp().run()
   File "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\app.py", line 828, in run
     runTouchApp()
   File "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\base.py", line 487, in runTouchApp
     EventLoop.window.mainloop()
   File "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\core\window\window_sdl2.py", line 606, in mainloo
p
     self._mainloop()
   File "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\core\window\window_sdl2.py", line 361, in _mainlo
op
     EventLoop.idle()
   File "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\base.py", line 336, in idle
     Clock.tick_draw()
   File "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\clock.py", line 490, in tick_draw
     self._process_events_before_frame()
   File "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\clock.py", line 640, in _process_events_before_fr
ame
     event.tick(self._last_tick, remove)
   File "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\clock.py", line 374, in tick
     ret = callback(self._dt)
   File "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\uix\boxlayout.py", line 175, in do_layout
     c.width = w
   File "kivy\properties.pyx", line 408, in kivy.properties.Property.__set__ (kivy\properties.c:4967)
   File "kivy\properties.pyx", line 446, in kivy.properties.Property.set (kivy\properties.c:5665)
   File "kivy\properties.pyx", line 501, in kivy.properties.Property.dispatch (kivy\properties.c:6314)
   File "kivy\_event.pyx", line 1223, in kivy._event.EventObservers.dispatch (kivy\_event.c:12615)
   File "kivy\_event.pyx", line 1129, in kivy._event.EventObservers._dispatch (kivy\_event.c:11914)
   File "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\uix\actionbar.py", line 617, in on_width
     self._layout_random()
   File "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\uix\actionbar.py", line 567, in _layout_random
     super_add(child, group_index)
   File "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\uix\boxlayout.py", line 213, in add_widget
     return super(BoxLayout, self).add_widget(widget, index)
   File "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\uix\layout.py", line 87, in add_widget
     return super(Layout, self).add_widget(widget, index)
   File "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\uix\widget.py", line 509, in add_widget
     % (widget, parent))
 kivy.uix.widget.WidgetException: Cannot add <kivy.uix.actionbar.ActionSeparator object at 0x00000000086EF9A8>, it alrea
dy has a parent <kivy.uix.actionbar.ActionOverflow object at 0x00000000086A1708>

Workaround

A workaround is to disable the actionbar:

        # Add each navigation toolbar and canvas to our BoxLayout
        # self.add_widget(nav1.actionbar)                                                     <==========
        self.add_widget(canvas)

[kayemen]

Has any progress been made with this issue?? Is there a solution?

[stale]

Thanks for your contribution!

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[razed11]

This probably should be posted against the Matplotlib Garden repository but that appears to have been abandoned a couple of years ago.

Same issue using 1.10.1.dev0. The garden examples appear to work fine--the action bars are displayed and function properly. In my case I'm building things in the constructor:

        canvas = self._figure.canvas

        navigator = NavigationToolbar2Kivy(canvas)

        self.ids.id_graph_board.add_widget(canvas)

        self.ids.id_graph_board.add_widget(navigator.actionbar)