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Android Programming for Beginners

Android Programming for Beginners

By : John Horton, Mayani
4.1 (47)
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Android Programming for Beginners

Android Programming for Beginners

4.1 (47)
By: John Horton, Mayani

Overview of this book

Android is the most popular OS in the world. There are millions of devices accessing tens of thousands of applications. It is many people's entry point into the world of technology; it is an operating system for everyone. Despite this, the entry-fee to actually make Android applications is usually a computer science degree, or five years’ worth of Java experience. Android Programming for Beginners will be your companion to create Android applications from scratch—whether you’re looking to start your programming career, make an application for work, be reintroduced to mobile development, or are just looking to program for fun. We will introduce you to all the fundamental concepts of programming in an Android context, from the Java basics to working with the Android API. All examples are created from within Android Studio, the official Android development environment that helps supercharge your application development process. After this crash-course, we’ll dive deeper into Android programming and you’ll learn how to create applications with a professional-standard UI through fragments, make location-aware apps with Google Maps integration, and store your user’s data with SQLite. In addition, you’ll see how to make your apps multilingual, capture images from a device’s camera, and work with graphics, sound, and animations too. By the end of this book, you’ll be ready to start building your own custom applications in Android and Java.
Table of Contents (32 chapters)
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31
Index

Scope and variables revisited


You might remember that in the Real World Methods project, the slightly disturbing anomaly was that variables in one method were not apparently the same as those from another, even if they did have the same name. If you declare a variable in a method, whether that is one of the lifecycle methods or one of our own methods, it can only be used within that method.

It is no use doing this in onCreate:

int a = 0;

And then, trying to do this in onPause or some other method:

a++;

We will get an error because a is only visible within the method it was declared in. At first, this might seem like a problem, but perhaps surprisingly, it is actually a very useful feature of Java.

The term used to describe this is "scope". A variable is said to be in a scope when it is usable and out of the scope when it is not. The topic of scope is best discussed along with classes, and we will in the next chapter, but as a sneak look at what lies ahead you might like to know that a class can...

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