Book Image

Android Programming for Beginners - Second Edition

By : John Horton
Book Image

Android Programming for Beginners - Second Edition

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 (35 chapters)
Android Programming for Beginners - Second Edition
Contributors
Preface
Other Books You May Enjoy
Index

Coding the LiveDrawingView class


Remember that LiveDrawingView cannot see the variables in LiveDrawingActivity. By using the constructor, LiveDrawingActivity is providing LiveDrawingView with a reference to itself (this) as well as the screen size in pixels contained in size.x and size.y. Add this constructor to LiveDrawingView. The code must go within the opening and closing curly braces of the class. It is convention, but not mandatory, to place constructors above other methods but after member variable declarations:

// The LiveDrawingView constructor
// Called when this line:
// mLiveDrawingView = new LiveDrawingView(this, size.x, size.y);
// is executed from LiveDrawingActivity
public LiveDrawingView(Context context, int x, int y) {
        // Super... calls the parent class
        // constructor of SurfaceView
        // provided by the Android API
        super(context);
}

To import the Context class, do the following:

  1. Place the mouse pointer on the red colored Context in the new constructor...