在kivy打开MDCard里面的matplotlib

Question

I've recently started working with Kivy and have been struggling with opening matplotlib graph inside the MDCard dedicated for it. All the available codes run solely the matplotlib graph class inside the App class but I want to access it from the second screen that I enter into and then by pressing the MDCard meant for it. Here, when I'm pressing the button nothing is showing. Here's my code. Kindly let me know what should I be doing:

project.py:

from kivymd.app import MDApp
from kivy.lang import Builder
from kivy.core.window import Window
from kivy.uix.screenmanager import Screen, ScreenManager
from kivymd.uix.card import MDCard
from kivymd.uix.boxlayout import MDBoxLayout
import matplotlib.pyplot as plt
import numpy as np
from kivy.garden.matplotlib.backend_kivyagg import FigureCanvasKivyAgg
import webbrowser

Window.clearcolor = (1, 1, 1, 1)
Window.size = (360, 600)

class ScreenOne(Screen):
    pass

class ScreenTwo(Screen):
    pass

x = [1,2,3,4,5]
y = [5, 12, 6, 9, 15]

signal_x = np.array(x)
signal_y = np.array(y)

plt.plot(signal_x,signal_y)

plt.xlabel("X-Axis")
plt.ylabel("Y-Axis")

plt.grid(True, color='lightgray')

class ScreenThree(Screen):
    def graph(self):
        app = MDApp.get_running_app()
        box = MDBoxLayout()
        box.add_widget(FigureCanvasKivyAgg(plt.gcf()))
        return box


sm = ScreenManager()
sm.add_widget(ScreenOne(name='screen1'))
sm.add_widget(ScreenTwo(name='screen2'))
sm.add_widget(ScreenThree(name='screen3'))


class KivyApp(MDApp):
    def build(self):
        self.theme_cls.primary_palette = "Cyan"
        self.theme_cls.primary_hue = "A700"
        self.theme_cls.theme_style = "Light"
        return Builder.load_file('project.kv')
    
    def url_Function(self):
        webbrowser.open('http://www.google.com')
    

    


KivyApp().run()

project.kv:

ScreenManager:
    ScreenOne:
    ScreenTwo:
    ScreenThree:

<ScreenOne>:
    name: 'screen1'
    MDFillRoundFlatButton:
        text: 'Get Started'
        pos_hint: {'center_x':0.5,'center_y':0.4}
        on_press: root.manager.current = 'screen2'

<ScreenTwo>:
    name: 'screen2'
    ScrollView:
        size: self.size
        GridLayout:
            size_hint_y: None
            height: self.minimum_height
            width: self.minimum_width
            cols: 1
            spacing: "20dp"
            padding: "20dp"

            MDCard:
                orientation: "vertical"
                padding: "8dp"
                size_hint: 1, None
                height: "210dp"
                elevation: 5
                border_radius: 10
                radius: [15]
                ripple_behavior: True
                on_press: app.url_Function()

                MDLabel:
                    text: 'Link'
                    bold: True
                    color: (64/255, 75/255, 122/255, 1)
                    font_size: 20
                    halign: 'center'

            MDCard:
                orientation: "vertical"
                padding: "8dp"
                size_hint: 1, None
                height: "210dp"
                elevation: 5
                border_radius: 10
                radius: [15]
                ripple_behavior: True
                on_press: root.manager.current = 'screen3'

                MDLabel:
                    text: 'Plot'
                    bold: True
                    color: (64/255, 75/255, 122/255, 1)
                    font_size: 20
                    halign: 'center'
                    valign: 'middle'

<ScreenThree>
    name: 'screen3'
    id: _box
    Button:
        text: 'Do it'
        on_release: _box.graph()

Answer 1

You are missing a box, which shall contain the FigureCanvasKivyAgg object.

project.py

class ScreenThree(Screen):
    def graph(self):
        self.ids.box_plot.add_widget(FigureCanvasKivyAgg(plt.gcf()))
        plt.close()

project.kv

<ScreenThree>:
    name: 'screen3'
    id: _box
    Button:
        text: 'Do it'
        on_release: _box.graph()
    MDBoxLayout:
        id: box_plot

This will show the plot after you click on the "Do it"-button of your 3rd screen.