Kivy Dropdown Tutorial for Beginners 2021

In this tutorial, we will be exploring the Kivy DropDown widget, which is a common user interface element used for displaying a list of options to the user. The DropDown widget is a great way to provide users with a list of options to choose from in a clean and organized manner. In this tutorial, we will cover how to create a DropDown widget in a Kivy application, add options to the DropDown, and handle user selection.

Step 1: Setting up the Kivy environment
Before we start creating our Kivy application with a DropDown widget, we need to make sure that we have the Kivy framework installed on our system. If you haven’t already installed Kivy, you can follow the installation instructions on the Kivy website (https://kivy.org/doc/stable/installation/installation.html) to set up the environment.

Step 2: Creating a basic Kivy application
To start building our Kivy application, let’s create a new Python file and import the necessary Kivy modules at the beginning of the file:

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button
from kivy.uix.dropdown import DropDown

Next, we can define a simple Kivy application class that will contain our DropDown widget:

class DropDownApp(App):
    def build(self):
        dropdown_btn = Button(text='Select an option', size_hint=(None, None), size=(200, 50))
        dropdown = DropDown()

        for i in range(5):
            btn = Button(text='Option %d' % i, size_hint_y=None, height=50)
            btn.bind(on_release=lambda btn: dropdown.select(btn.text))
            dropdown.add_widget(btn)

        dropdown_btn.bind(on_release=dropdown.open)
        dropdown.bind(on_select=lambda instance, x: setattr(dropdown_btn, 'text', x))

        layout = BoxLayout(orientation='vertical')
        layout.add_widget(dropdown_btn)

        return layout

In this code snippet, we have created a DropDownApp class that inherits from the App class of Kivy. We define a method build() which returns the root widget of the application. Inside the build() method, we create a Button named dropdown_btn that will act as the main button for opening the DropDown widget. We also create a DropDown object and populate it with options using a for loop. Each option is represented as a Button widget with a specific text label and binding the on_release event to select the option when the button is clicked.

We then bind the on_release event of the main button dropdown_btn to open the DropDown when clicked. Finally, we bind the on_select event of the DropDown to update the text of the main button with the selected option.

Step 3: Running the application
To run the Kivy application with the DropDown widget, we just need to create an instance of the DropDownApp class and call its run() method:

if __name__ == '__main__':
    DropDownApp().run()

Save the file and run it using a Python interpreter to see the DropDown widget in action. You should see a main button labeled "Select an option". When you click on the main button, a list of options will be displayed in a dropdown menu, and selecting an option will update the text of the main button accordingly.

This tutorial covers the basic usage of the DropDown widget in Kivy applications. You can further customize the appearance and behavior of the DropDown widget by exploring other properties and methods provided by the DropDown class in the Kivy documentation. I hope you found this tutorial helpful and that you are now able to create your own DropDown widgets in Kivy applications.