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Android Programming for Beginners

Android Programming for Beginners

By : John Horton
3.8 (13)
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Android Programming for Beginners

Android Programming for Beginners

3.8 (13)
By: John Horton

Overview of this book

Are you trying to start a career in programming, but haven't found the right way in? Do you have a great idea for an app, but don't know how to make it a reality? Or maybe you're just frustrated that in order to learn Android, you must know Java. If so, then this book is for you. This new and expanded second edition of Android Programming for Beginners will be your companion to create Android Pie applications from scratch. We will introduce you to all the fundamental concepts of programming in an Android context, from the basics of Java to working with the Android API. All examples use the up-to-date API classes, and 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 and store your user's data with SQLite. In addition, you'll see how to make your apps multilingual, draw to the screen with a finger, 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 (33 chapters)
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32
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 do have the same name. If you declare a variable in a method, whether that is one of the life cycle 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. At first, this might seem like a problem but surprisingly, it is actually a very useful feature of Java.

I have already mentioned that the term used to describe this is scope. A variable is said to be in scope when it is usable and out of scope when it is not. The topic of scope is best discussed along with classes, and we will do so in Chapter 10, Object-Oriented programming, and Chapter 11, More Object-Oriented Programming...

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