Python Kivy: Create a FloatLayout with access to Setting panel and running command

Question

I'm currently trying to learn while using the Kivy GUI language. I'm trying to create a layout with different widget on it (button, file browser ...) with one of the button accessing a custom Setting panel to set some parameters and then a button to run a command using these parameters.

I'm having trouble to get the command button working and it is probably a simple object oriented problem but I can't see what's wrong. Any help would be greatly appreciated. Also if anyone have an idea how to use the command button ( btn) to access some of the values stored from the settings it would be great.

Here is my code so far:

# main.py

from kivy.app import App
from kivy.lang import Builder

from kivy.uix.boxlayout import BoxLayout
from kivy.uix.settings import SettingsWithSidebar
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.button import Button

from settingsjson import settings_json

Builder.load_string('''
<Interface>:
    Button:
        text: 'Analysis Settings'
        pos_hint: {"x": 0.2, 'y': 0.3}
        on_release: app.open_settings()
        size_hint: 0.2, 0.2

''')                               

class Interface(FloatLayout):       #
    pass


class SettingsApp(App):
    def build(self):

        #Color setting#
        blue = (0, 0, 1.5, 2.5)

        self.settings_cls = SettingsWithSidebar
        self.use_kivy_settings = False
        setting = self.config.get('example', 'boolexample')

        btn = Button(text='Run!',
                     background_color=blue,
                     size_hint=(.2, .2),
                     pos_hint={'x':.5, 'y':.3})
        btn.bind(on_press=self.command1)
        Interface.add_widget(Interface.btn)

        return Interface()

    def command1(self, event):
        print("button touched")

    def build_config(self, config):
        config.setdefaults('example', {
            'boolexample': True,
            'numericexample': 10,
            'optionexample': 'Analysis type1',
            'stringexample': 'PO12345'})

    def build_settings(self, settings):
        settings.add_json_panel('Parameter of Analysis',
                                self.config,
                                data=settings_json)

    def on_config_change(self, config, section,
                         key, value):
        print config, section, key, value

SettingsApp().run()

settings.ini

[example]
boolexample = 1
optionexample = Analysis type1
stringexample = 46464, hdfhf, jhdgfjhf, hjdgfjhf
numericexample = 455
optionsexample = Analysis type2

settingsjson.py

import json

settings_json = json.dumps([
    {'type': 'title',
     'title': 'Analysis parameters'},
    {'type': 'bool',
     'title': 'Add accessin number list?',
     'desc': 'Choose if you want to add an Accession list to your analysis',
     'section': 'example',
     'key': 'boolexample'},
    {'type': 'numeric',
     'title': 'Select maximum number of protei to display',
     'desc': 'This will determine maximum protein displayed on graph',
     'section': 'example',
     'key': 'numericexample'},
    {'type': 'options',
     'title': 'Selection your Analysis option',
     'desc': 'Choose for an analysis option',
     'section': 'example',
     'key': 'optionsexample',
     'options': ['Analysis type1', 'Analysis type2', 'Analysis type3']},
    {'type': 'string',
     'title': 'Type specific accession number to display',
     'desc': 'Type some accession numbers to display',
     'section': 'example',
     'key': 'stringexample'}])

Answer 1

I'm having trouble to get the command button working and it is probably a simple object oriented problem but I can't see what's wrong.

You wrote:

Interface.add_widget(Interface.btn)

Have a look at your Interface class--there's no btn property defined anywhere. However, prior to that line you constructed a widget named btn, so you should write:

Interface.add_widget(btn)

That leads to another error:

TypeError: unbound method add_widget() must be called with Interface instance as first argument (got Button instance instead)

When you call a method with a class name, it's different than when you call a method with an instance of the class:

class Dog:
    def bark(self):
        print('woof')

d = Dog()
d.bark()


Dog.bark()


--output:--
woof

Traceback (most recent call last):
  File "main.py", line 9, in <module>
    Dog.bark()
TypeError: unbound method bark() must be called with
   Dog instance as first argument (got nothing instead) #<****HEY!

When you call bark() with an instance of the Dog class, python automatically passes the instance as the first argument to the method, which gets assigned to the variable self. That doesn't happen when you call the method with the class.

To fix that error, you need to change the line:

Interface.add_widget(btn)

to:

i = Interface()
i.add_widget(btn)

Or, more tortuously:

class Dog:
    def __init__(self):
        print(self)

    def bark(self):
        print(self)
        print('woof')

d = Dog()
Dog.bark(d) #<*** Manually pass an instance.

--output:--
woof

Answer 2

Also if anyone have an idea how to use the command button ( btn) to access some of the values stored from the settings it would be great.

The App class has a config property, which gives you access to all the settings:

class SettingsApp(App):
    ...
    ...
    def onpress_button(self, button):
        print "button touched"
        config = self.config

        print config.getint("example", "numericexample")
        print config.getfloat("example", "numericexample")
        print config.getboolean("example", "boolexample")

        print config.get("example", "stringexample")
        print config.getdefault("example", "non-existent", "hello")

        print config.items('example')


--output:--
button touched
10
10.0
True
PO12345
hello
[('boolexample', 'True'), ('optionexample', 'Analysis type1'), ('stringexample', 'PO12345'), ('numericexample', '10')]

Check out the python docs for ConfigParser as well as the kivy docs for the Config object to see all the methods that are available.