April monpaysofchlesspi.ml • Chart 1 > droidcon > A. Schreiber • Developing Apps for Android and Other Platforms with Kivy and Python > Description. Build mobile apps efficiently with Kivy, the Python-powered graphical toolkit for creating natural user interfaces with elegant multitouch support. Build mobile apps efficiently with Kivy, the Python-powered graphical toolkit for creating natural user interfaces with elegant multitouch support. With this hands-on guide, you’ll learn step-by-step how to build and deploy a complete Kivy app for iOS and Android devices.
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The first chapter is an introduction to Kivy and KV language. You will learn how to create basic widgets in this chapter and dig a little into KV too as well as start the overarching project of the book.
Chapter 3 digs into how to manipulate the widgets. You also learn how to retrieve data from the internet using Kivy.
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It also discusses adding icons to your application. Chapter 6 is all about persistence in Kivy world. How do you save your settings? In Chapter 7, we learn about gestures. How to record gestures, touch events, firing events based on gestures, etc.
Kivy handles a lot of the back-end requirements for you. For things like where the mouse is, how a button should react when clicked, or, even how to manage multiple screens, Kivy has your back! This isn't required, but necessary if you're using new features of Kivy. We're inheriting from Kivy's App class. Our build method is an expected method for Kivy. Within our build, we're just returning a simple Label, which is just displaying "Hello World.
OOP can be a bit confusing, though it doesn't have to be! If you're confused about OOP, check out the. You will probably even make mistakes and omissions as you type the examples from this book.
You will eventually encounter these regularly at least, if you type like I do. I suggest you force one now so you know what to look for. By default, the BoxLayout places each of its child widgets side by side, from left to right, giving each one an equal amount of space. If you now run python main.
It would not be difficult to change the labels in the root widget to some buttons and text boxes to create the Add Location form I have in mind.
But that would make things rather complicated later, when you need to remove all those widgets from the view to put other data for example, a forecast on display. Further, if the user later wanted to add another location, it would be tricky to restore all the Add Location widgets.
Instead, create a custom AddLocationForm widget that encapsulates the text entry, search button, location button, and search results into a single widget. Then set the root widget to be an instance of that custom widget instead. The root widget is now a custom widget named AddLocationForm.
The new custom class is defined here. The symbol in the KV language indicates that the class is extending BoxLayout using inheritance. This means that the new widget is a BoxLayout and can do all the things a BoxLayout can do, such as lay out its children.
The angle brackets tell the KV language that this is a new class rule, not a root widget. AddLocationForm is a BoxLayout like in the previous example, but you are setting its orientation property to vertical.
The Mouse Vs. The Python
This will force its child elements to appear one above the other. The child elements in this case are another BoxLayout this one is horizontal , and a ListView. First, the text box and two buttons are way too tall. This is fairly easy to take care of in terms of lines of code. However, I find setting proportions on Kivy widgets to be confusing.
I hope to spare you that frustration by giving a thorough explanation in this section! It is up to the Layout object to determine what size its child widgets should be. It is allowed to take two types of advice from its children, should the children choose to provide it, but it is also free to ignore that advice.
For example, a horizontal BoxLayout will always make its children the same height as itself, no matter what the child requests this can cause extensive problems if the child widget is in its teens.
The two types of advice the child can give its parent layout are size hints and absolute sizes. For each type of advice, the child widget can set properties in the x dimension horizontally and the y dimension vertically. In addition, it is possible to combine the horizontal and vertical settings in the case where you need to explicitly set both of them.
This is unecessary with BoxLayout , since it always uses maximum space in one direction, but can be useful with other layouts. Thus, there are technically six different proportion advice properties that you can set on any given widget class:.
Sometimes having widget sizes calculated relative to the sizes of other widgets is exactly what you need. Other times, you need to control the size in one or both dimensions a little more accurately. This is where the width and height properties come in.
The width and height values themselves are pretty easy to interpret. They can be integer values, in which case they refer to the pixel size of the widget on the screen. However, you can also pass string values such as "1cm" , "0. This is almost always a good idea, because modern devices can have an extremely wide variety of pixel densities. A pixel on a cheap laptop might be three times the size of a pixel on a high-end smartphone, and the disparity is even larger for so-called retina displays.
On top-end displays, a display pixel might be 3 or 4 real pixels wide. This is useful, since touch interfaces need to provide a bit more room for widgets to accommodate the clumsy size of the human finger.
Creating Apps In Kivy
Remember that a given layout is free to ignore the width and height properties if it so chooses. Keep this knowledge close to hand, and you should I hope never have to go through the trauma that I did to figure out Kivy sizing! Pay close attention to the indentation so you can tell what size property has been set on which widget. Remember, there are two BoxLayout objects.
You are setting the inner by default, horizontal BoxLayout to have an explicit height of 40 display pixels. This means the TextInput and two button widgets inside will be constrained to that height, since they expand to fill the full height of the parent.
The ListView has not been given any additional size information. Programming is a task that is best learned by doing, not reading, studying, watching, or listening. Take some time to try things and mess up. I close each chapter with a set of explorations you can use to guide your study.
Think of them as topics. Programming is best facilitated by a sense of wonder. Here are a few ideas to get you started:. Stay ahead with the world's most comprehensive technology and business learning platform.
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Introducing Kivy. Kivy has elegant built-in support for multitouch devices. Kivy is the only viable way to code in Python on mobile devices. Kivy allows you to maintain a single application for numerous operating systems.
The Mouse Vs. The Python
Has beginner to intermediate programming skills and has read the Python tutorial Is not intimately acquainted with advanced Python concepts, but is eager to learn Wants to learn about programming workflow, not just Kivy Has a good sense of humor Owns an Android or iOS device. The Hard Part. Installing on Mac OS.
Installing on Windows.
Writing Code: The Easy Part. The most basic Kivy app. A slightly less basic Kivy app. Introducing the KV Language.
Simple KV language file. User Interface Design.Events and Properties.
Regardless of whether the cached widget was constructed from scratch or previously stored, add it back into the window. Remember to do the same thing in the more complicated ClearConditions class. That single line of code can, and should, call a Responding to Events 23 www. There are, as always, numerous activities you can try to extend your knowledge on your own.
Alternating values are x and y coordinates in the coordinate space of the window.
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