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

Android coordinate system


As we will see, drawing a Bitmap is trivial. But the coordinate system that we use to draw our graphics onto needs a brief explanation.

Plotting and drawing

When we draw a Bitmap object to the screen, we pass in the coordinates we want to draw the object at. The available coordinates of a given Android device depend upon the resolution of its screen.

For example, the Google Pixel phone has a screen resolution of 1920 pixels (across) by 1080 pixels (down) when held in landscape view.

The numbering system of these coordinates starts in the top left-hand corner at 0,0, and proceeds down and to the right until the bottom-right corner is pixel 1919, 1079. The apparent 1-pixel disparity between 1920/ 1919 and 1080/ 1079 is because the numbering starts at 0.

So, when we draw a Bitmap or anything else to the screen (such as Canvas circles and rectangles), we must specify an x, y coordinate.

Furthermore, a Bitmap (or Canvas shape), of course, comprises many pixels. So, which...