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Kivy Cookbook

By : Hugo Solis, Solis

2.5 (2)

Kivy Cookbook

2.5 (2)

By: Hugo Solis, Solis

Overview of this book

Kivy is an open-source Python library for rapid development of applications that make use of innovative user interfaces, such as multi-touch apps. It is a promising Python framework to develop UI and UX apps in a cross-platform environment, under the Python philosophy. Kivy Cookbook is a practical book that will guide you through the Kivy framework to develop apps and get your apps ready for distribution in App Store and Android devices. You will start off with installing Kivy and building your interfaces. You will learn how to work the accelerometer and create custom events. Then, you will understand how to use the basics, buttons, labels and text inputs and manipulate the widget tree. Next, you will be able to work with manipulating instructions, create an atlas and layouts. Moving on, you will learn packing for Windows and packing for iOS, and use TestDrive. By the end of the book, you will have learnt in detail the relevant features and tools in Kivy and how to create portable packages to distribute your apps in the most used platforms.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Sections

Conventions

Reader feedback

Customer support

Free Chapter

1. Kivy and the Kv Language

1. Kivy and the Kv Language

Introduction

Installing Kivy

Building your interfaces

Declaring properties within a class

Relating Python code and the Kv language

Referencing widgets

Accessing widgets defined inside the Kv language in your Python code

Reusing styles in multiple widgets

Designing with the Kv language

Running your code

Using Kivy garden

2. Input, Motion, and Touch

2. Input, Motion, and Touch

Introduction

Using the mouse

Evolving to the touchscreen

Working with the accelerometer

Using the gyroscope

The differences between the touch and motion events

Recognizing touch shapes

Detecting multitapping

Grabbing touch events

Recording gestures

3. Events

3. Events

Introduction

Scheduling a one-time event

Scheduling a repetitive event

Triggering events

Defining widget events

Creating custom events

Attaching callbacks

Declaring a property

Compounding properties

4. Widgets

4. Widgets

Introduction

Using the basics: buttons, labels, and text inputs

Manipulating the widget tree

Traversing the tree

Using swappable widgets

Organizing with layouts

Using FloatLayout

Using BoxLayout

Using GridLayout

Using StackLayout

Using RelativeLayout

Using AnchorLayout

Working with ActionBar

5. Graphics – Canvas and Instructions

5. Graphics – Canvas and Instructions

Introduction

Separating with the screen manager

Using drawing instructions

Using context instructions

Working with manipulating instructions

Rotating, translating, and scaling the canvas

Modifying with multitouching

Storing and retrieving the coordinate space context

Introducing animations

6. Advanced Graphics – Shaders and Rendering

6. Advanced Graphics – Shaders and Rendering

Introduction

Using Carousel

Creating and using Atlas

Creating layouts

Editing shaders

Creating widgets

Creating your own shader

Rendering in a Framebuffer

Optimizing graphics

7. The API in Detail

7. The API in Detail

Introduction

Getting to know the API

Using the asynchronous data loader

Logging objects

Parsing

Applying utils

Leveraging the factory object

Working with audio

Working with video

Working with a camera

Using spelling

Adding effects

Advanced text manipulation

8. Packaging our Apps for PC

8. Packaging our Apps for PC

Introduction

Packaging for Windows

Including multimedia for Windows

Running apps in Windows

Packaging for Mac OS

Including multimedia for Mac OS

Running apps in Mac OS

Packaging for Linux

Including multimedia for Linux

Running apps in Linux

9. Kivy for Mobile Devices

9. Kivy for Mobile Devices

Introduction

Packaging for iOS

Resizing the screen into iOS

Leveraging mobile features in iOS

Preparing for the App Store

Packaging for Android

Resizing the screen into Android

Leveraging mobile features in Android

Index

Index

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Accessing widgets defined inside the Kv language in your Python code

This recipe will teach you how to access definitions inside the Kv language in your Python code and vice versa.

Getting ready

This recipe will use button, a very common widget that we also used in the last recipe.

How to do it…

This recipe follows as:

Make a rule for the widget.
Define a button.
Give it an ID.
Define the label for the button.

In the action, call a method in the Python code:

<MyW>:
    Button:
        id: b1
        text: 'Press to smash'
        on_release: root.b_smash()

Create the Python code with the method:

import kivy
kivy.require('1.8.0') # replace with your current kivy version !

from kivy.app import App
from kivy.uix.widget import Widget

class MyW(Widget):
    def b_smash(self):
        self.ids.b1.text = 'Pudding'

class e7App(App):
    def build(self):
        return MyW()

if __name__ == '__main__':
    e7App().run()

How it works…

In the Kv Language file, we have the following in the first line:

<MyW>:

This is the name of the widget, a simple button. The second line is:

Button:

This is the button definition. The third line is:

id: b1

This gives the button an ID b1. The fourth line is:

    text: 'Press to smash'

This makes the initial text on the button 'Press to smash'. The fifth line is:

    on_release: root.b_smash()

The preceding line is making a call to the Python code; it refers the method b_smash() of the root class MyW.

The fifth line in the Python code is:

class MyW(Widget):

This is the definition of the class related to the Widget. The sixth line is:

def b_smash(self):

This defines the method b_smash(), which is accessed by the Kv language file. The seventh line is:

self.ids.b1.text = 'Pudding'

This accesses the widget defined in the Kv language file, specifically the button with its ID, and changes the text displayed in the button to the text Pudding.

See also

If you want to run your interface, take a look at our recipe Running your code, and to get more details about widgets, see the recipes in Chapter 4, Widgets.

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