Book Image

Android Programming for Beginners

By : John Horton, Mayani
Book Image

Android Programming for Beginners

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)
31
Index

Arrays and ArrayLists are polymorphic


We already know that we can put objects into arrays and ArrayList. But being polymorphic means that they can handle objects of multiple different types as long as they have a common parent type, all within the same array or ArrayList.

In Chapter 9, Object-Oriented Programming, you learned that polymorphism roughly means different forms. But what does it mean to us in the context of arrays and ArrayList?

Boiled down to its simplest, any subclass can be used as part of the code that uses the super class.

For example, if we have an array of Animals, we could put any object that is a type, that is a subclass of Animal in the Animal array, perhaps, Cats and Dogs.

This means that we can write code that is simpler and easier to understand and easier to modify or change:

// This code assumes we have an Animal class
// And we have a Cat and Dog class that extends Animal
Animal myAnimal =  new Animal();
Dog myDog = new Dog();
Cat myCat = new Cat();
Animal [] myAnimals...