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Kivy Cookbook
Kivy Cookbook

Kivy Cookbook: Enhance your skills in developing multi-touch applications with Kivy

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Kivy Cookbook

Chapter 2. Input, Motion, and Touch

In this chapter, we will cover:

  • 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

Introduction

The Kivy framework is able to handle most common types of input and actions such as mouse, touchscreen, accelerometer, and gyroscope that will be reviewed in this chapter. It handles the native multitouch protocols on the following platforms: Tuio, WM_Touch, MacMultitouchSupport, MT Protocol A/B, and Android.

The class of all input events is motion event. It generates two kinds of events; one of them is touch events—a motion event that contains at least an x and y position. All the touch events are dispatched across the widget tree. The no-touch events are the rest. The accelerometer is a continuous event, without position. It never starts or stops. These events are not dispatched across the widget tree.

Using the mouse

This recipe will teach you how to use the first kind of input, probably the most used, the mouse. We will consider the mouse input as a touch event, so the (x, y) position of the touch (0-1 range) will be scaled to the window size (width/height) and dispatched to the following:

  • on_touch_down: An event is fired when a touch down event is initiated. Subsequently, the respective widget's on_touch_down() method is called.
  • on_touch_move: An event is fired when a touch event moves (changes location). Subsequently, the respective widget's on_touch_move() method is called.
  • on_touch_up: An event is fired when a down event is released (terminated). Subsequently, the respective widget's on_touch_up() method is called.

Getting ready

In this recipe, we will use the Kv language for the design of the widgets, so you will need to be familiar with the language or have completed the previous chapter. Also, this recipe will use the common Button widget for reference.

How to do it...

Evolving to the touchscreen

In this recipe, we are evolving to the touchscreen. Here, you will see the basic differences between the mouse and the touchscreen. This will give us more options than with the mouse device.

Getting ready

For this recipe, we will use the Kv language for the design of the widgets, so make sure that you are confident with it and refresh your knowledge if necessary. Also, this recipe will use the common button and label widgets for reference. Obviously, to get more benefit, a touchscreen device is useful to run the code.

How to do it…

Perform the following steps:

  1. In the KV file, declare the button and the label:
    <MyW>:
        Button:
            id: button1
            text: 'Hello'
        Label:
            id: label1
            pos: 100, 100
            text: 'My label before press the screen'
  2. In the class of the widget in the Python code, we need to override the method on_touch_down
  3. Change the button text with the information in touch.button
  4. Change the label text...

Working with the accelerometer

Nowadays, it is common that mobile devices are equipped with an accelerometer. Thereby, it is relevant to consider this input to develop fancy apps. The accelerometer is one kind of event that is considered as a no-touch event because it has neither start nor an end, it is always providing information.

Getting ready

In this recipe, we will use the Kv language for the design of the widgets, so, again, you will need to be familiar with the Kv language. Also, this recipe will use the common button and label widgets for reference. Obviously, to get more benefit, a device with an accelerometer is useful to run the code.

It is necessary to install a package for the use of the accelerometer in any mobile device; there is a way to deal with every specific device, but we do not have to reinvent the wheel. Let's use a Plyer package, which is an effort from many of the Kivy developers. To install the package from the shell, use:

$ sudo pip plyer install

Here where we...

Using the gyroscope

Mobile devices today also have a gyroscope. The gyroscope is considered as a no-touch event. This kind of event does not have a start or an end; it is always providing information.

Getting ready

For this recipe, we will use the Kv language for the design of the widgets. Also, this recipe will use the common button and label widgets for reference. Obviously, to run the code of this recipe properly, a device with a gyroscope is necessary.

It is necessary to install a package to use the gyroscope with any mobile device. While there is a way to deal with specific devices, we do not have to reinvent the wheel. Let's use the plyer package, which is an effort from many of the Kivy developers. To install the package from the shell, use:

$ sudo pip plyer install

How to do it…

To complete this recipe, follow these steps:

  1. In the KV file, define the four labels and the button:
    <Acce>:
        Label:
            id: label1
            pos: 150, 300
            text: 'X: '
    
    ...

The differences between the touch and motion events

There is a key difference between touch and motion events. A motion event is a continuous succession of many touch events. However, we also know that a touch event always has the pos profile, namely position information. The motion event, however, is not dispatched throughout the widget tree.

Getting ready

In this recipe, we will use the Kv language for the design of the widgets, so we assume that the reader is familiar with the Kv language or did the lecture of the first chapter. Also, this recipe will use the common button widget for reference.

How to do it…

Use this recipe and follow these steps:

  1. First, in the KV file, define a button:
    <MyW>:
        Button:
            id: button1
            pos: 0,0
            text: 'Hello'
  2. In the class of the widget in the Python code, we need to override the method on_touch_move.
  3. Change the button's position with the information in touch.pos:
    import kivy
    kivy.require('1.9.0') 
    
    from...

Introduction


The Kivy framework is able to handle most common types of input and actions such as mouse, touchscreen, accelerometer, and gyroscope that will be reviewed in this chapter. It handles the native multitouch protocols on the following platforms: Tuio, WM_Touch, MacMultitouchSupport, MT Protocol A/B, and Android.

The class of all input events is motion event. It generates two kinds of events; one of them is touch events—a motion event that contains at least an x and y position. All the touch events are dispatched across the widget tree. The no-touch events are the rest. The accelerometer is a continuous event, without position. It never starts or stops. These events are not dispatched across the widget tree.

Using the mouse


This recipe will teach you how to use the first kind of input, probably the most used, the mouse. We will consider the mouse input as a touch event, so the (x, y) position of the touch (0-1 range) will be scaled to the window size (width/height) and dispatched to the following:

  • on_touch_down: An event is fired when a touch down event is initiated. Subsequently, the respective widget's on_touch_down() method is called.

  • on_touch_move: An event is fired when a touch event moves (changes location). Subsequently, the respective widget's on_touch_move() method is called.

  • on_touch_up: An event is fired when a down event is released (terminated). Subsequently, the respective widget's on_touch_up() method is called.

Getting ready

In this recipe, we will use the Kv language for the design of the widgets, so you will need to be familiar with the language or have completed the previous chapter. Also, this recipe will use the common Button widget for reference.

How to do it…

Follow the steps...

Evolving to the touchscreen


In this recipe, we are evolving to the touchscreen. Here, you will see the basic differences between the mouse and the touchscreen. This will give us more options than with the mouse device.

Getting ready

For this recipe, we will use the Kv language for the design of the widgets, so make sure that you are confident with it and refresh your knowledge if necessary. Also, this recipe will use the common button and label widgets for reference. Obviously, to get more benefit, a touchscreen device is useful to run the code.

How to do it…

Perform the following steps:

  1. In the KV file, declare the button and the label:

    <MyW>:
        Button:
            id: button1
            text: 'Hello'
        Label:
            id: label1
            pos: 100, 100
            text: 'My label before press the screen'
  2. In the class of the widget in the Python code, we need to override the method on_touch_down

  3. Change the button text with the information in touch.button

  4. Change the label text with the information in...

Working with the accelerometer


Nowadays, it is common that mobile devices are equipped with an accelerometer. Thereby, it is relevant to consider this input to develop fancy apps. The accelerometer is one kind of event that is considered as a no-touch event because it has neither start nor an end, it is always providing information.

Getting ready

In this recipe, we will use the Kv language for the design of the widgets, so, again, you will need to be familiar with the Kv language. Also, this recipe will use the common button and label widgets for reference. Obviously, to get more benefit, a device with an accelerometer is useful to run the code.

It is necessary to install a package for the use of the accelerometer in any mobile device; there is a way to deal with every specific device, but we do not have to reinvent the wheel. Let's use a Plyer package, which is an effort from many of the Kivy developers. To install the package from the shell, use:

$ sudo pip plyer install

Here where we are...

Left arrow icon Right arrow icon

Description

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.

What you will learn

  • Access widgets defined inside Kv language in your Python code Handle Kivy events to control widgets, touches, the mouse, the keyboard, and animations Recognize touch shapes and detecting multi-tapping Create custom events and declare properties Organizing your layouts while working with the ActionBar Store and retrieve the coordinate space context Create your own shader and render in a framebuffer Leverage Factory objects, multi-touch in iOS and multi-touch in Android
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Publication date : Aug 21, 2015
Length: 246 pages
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Language : English
ISBN-13 : 9781783987382
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Length: 246 pages
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ISBN-13 : 9781783987382
Category :
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Table of Contents

10 Chapters
1. Kivy and the Kv Language Chevron down icon Chevron up icon
2. Input, Motion, and Touch Chevron down icon Chevron up icon
3. Events Chevron down icon Chevron up icon
4. Widgets Chevron down icon Chevron up icon
5. Graphics – Canvas and Instructions Chevron down icon Chevron up icon
6. Advanced Graphics – Shaders and Rendering Chevron down icon Chevron up icon
7. The API in Detail Chevron down icon Chevron up icon
8. Packaging our Apps for PC Chevron down icon Chevron up icon
9. Kivy for Mobile Devices Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

Customer reviews

Rating distribution
Full star icon Full star icon Half star icon Empty star icon Empty star icon 2.5
(2 Ratings)
5 star 0%
4 star 50%
3 star 0%
2 star 0%
1 star 50%
SL Sep 10, 2015
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
This book covers Kivy for Python programmation language. Kivy helps you build graphical interfaces that run on all PC platforms and also on android and IOS. http://kivy.org/The cookbook format is quite convenient because it gives several recipes from extremely basic to more advanced ones. From launching a "hello world" app to packaging your app for distribution.So it's a good purchase and it was worth reading it.
Amazon Verified review Amazon
jooster Sep 07, 2017
Full star icon Empty star icon Empty star icon Empty star icon Empty star icon 1
I cannot recommend this book. Though the format fits my work/learning style, the example code is riddled with errors, problems and omissions. Right of the bat, the very first example (hello world) does not work as described. The remainder of the book is an exercise in frustration. I (tried to) made it through several examples before moving onto something else.
Amazon Verified review Amazon
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