Book Image

Android Programming for Beginners - Third Edition

By : John Horton
Book Image

Android Programming for Beginners - Third Edition

By: John Horton

Overview of this book

Do you want to make a career in programming but don’t know where to start? Do you have a great idea for an app but don't know how to make it a reality? Or are you worried that you’ll have to learn Java programming to become an Android developer? Look no further! This new and expanded third edition of Android Programming for Beginners will be your guide to creating Android applications from scratch. The book starts by introducing you to all the fundamental concepts of programming in an Android context, from the basics of Java to working with the Android API. You’ll learn with the help of examples that use up-to-date API classes and are created within Android Studio, the official Android development environment that helps supercharge your mobile application development process. After a crash course on the key programming concepts, you’ll explore Android programming and get to grips with creating applications with a professional-standard UI using fragments and storing user data with SQLite. This Android Java book also shows you how you can make your apps multilingual, draw on the screen with a finger, and work with graphics, sound, and animations. By the end of this Android programming book, you'll be ready to start building your own custom applications in Android and Java.
Table of Contents (30 chapters)

Polymorphism

We already know that polymorphism means different forms. But what does it mean to us?

Boiled down to its simplest:

Any subclass can be used as part of the code that uses the super class.

This means we can write code that is simpler and easier to understand, and easier to change.

Also, we can write code for the super class and rely on the fact that no matter how many times it is sub-classed, within certain parameters, the code will still work. Let's discuss an example.

Suppose we want to use polymorphism to help to write a zoo management app. We will probably want to have a method such as feed. We will probably want to pass a reference to the animal to be fed into the feed method. This might seem like we need to write a feed method for each and every type of Animal.

However, we can write polymorphic methods with polymorphic return types and arguments:

Animal feed(Animal animalToFeed){
   // Feed any animal here
   ...