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)

Adding custom buttons to the screen

We need to let the user control when to start another drawing and clear the screen of their previous work. We need the user to be able to decide if and when to bring the drawing to life. To achieve this, we will add two buttons to the screen, one for each of the tasks.

Add the members highlighted next in the LiveDrawingView class:

// These will be used to make simple buttons
private RectF mResetButton;
private RectF mTogglePauseButton;

We now have two RectF instances. These objects hold four floating-point coordinates each, one coordinate for each corner of our two proposed buttons.

Initialize the positions in the constructor of LiveDrawingView:

// Initialize the two buttons
mResetButton = new RectF(0, 0, 100, 100);
mTogglePauseButton = new RectF(0, 150, 100, 250);

Add the import for the RectF class:

import android.graphics.RectF;

Now we have added actual coordinates for the buttons. If you visualize the coordinates on the...