Android 9 Development Cookbook

Over 100 recipes and solutions to solve the most common problems faced by Android developers, 3rd Edition

Rick Boyer

• Publisher: Packt Publishing
• Year: 2018
• Edition: 3
• eBook ISBN:
  9781788622967
• Topic: Computer Science
• Subtopic: Application Development
• Index: Computer Science

Build feature-rich, reliable Android Pie apps with the help of more than 100 proven industry standard recipes and strategies.

Key Features

• Uncover the latest features in Android 9 Pie to make your applications stand out
• Develop Android Pie applications with the latest mobile technologies, from set up to security
• Get up-to-speed with Android Studio 3 and its impressive new features

Book Description

The Android OS has the largest installation base of any operating system in the world. There has never been a better time to learn Android development to write your own applications, or to make your own contributions to the open source community! With this extensively updated cookbook, you'll find solutions for working with the user interfaces, multitouch gestures, location awareness, web services, and device features such as the phone, camera, and accelerometer. You also get useful steps on packaging your app for the Android Market. Each recipe provides a clear solution and sample code you can use in your project from the outset. Whether you are writing your first app or your hundredth, this is a book that you will come back to time and time again, with its many tips and tricks on the rich features of Android Pie.

What you will learn

• Develop applications using the latest Android framework while maintaining backward-compatibility with the support library
• Create engaging applications using knowledge gained from recipes on graphics, animations, and multimedia
• Work through succinct steps on specifics that will help you complete your project faster
• Add location awareness to your own app with examples using the latest Google Play services API
• Utilize Google Speech Recognition APIs for your app

Who this book is for

If you are new to Android development and want to take a hands-on approach to learning the framework, or if you are an experienced developer in need of clear working code to solve the many challenges in Android development, you will benefit from this book. Either way, this is a resource you'll want to keep on your desk as a quick reference to help you solve new problems as you tackle more challenging projects.

Graphics and Animation

In this chapter, we will cover the following topics:

• Scaling down large images to avoid Out of Memory exceptions
• A transition animation: Defining scenes and applying a transition
• Creating a Compass using sensor data and RotateAnimation
• Creating a slideshow with ViewPager
• Creating a Card Flip Animation with Fragments
• Creating a Zoom Animation with a Custom Transition
• Displaying an animated image (GIF/WebP) with the new ImageDecoder library
• Creating a circle image with the new ImageDecoder

Introduction

Animations can be both visually appealing and functional, as demonstrated with the simple button press. The graphical representation of the button press brings the app alive, plus it provides a functional value by giving the user a visual response to the event.

The Android Framework provides several animation systems to make it easier to include animations in your own application. They include the following:

• View Animation (the original animation system): It usually requires less code but has limited animation options
• Property Animation: It's a more flexible system, allowing the animation of any property of any object
• Drawable Animation: It uses drawable resources to create frame-by-frame animations (like a movie)

The Property Animation system was introduced in Android 3.0, and it is usually preferred over the View Animation because of the flexibility. The main drawbacks to the View Animation include the following:

• Limited aspects of what can be animated, such as scale and rotation
• Can only animate the contents of the view; it cannot change where on the screen the view is drawn (so it cannot animate moving a ball across the screen)
• Can only animate View objects

Here is a simple example demonstrating a View Animation to "blink" a view (a simple simulation of a button press):

Animation blink =AnimationUtils.loadAnimation(this,R.anim.blink); view.startAnimation(blink); 

Here are the contents for the blink.xml resource file, located in the res/anim folder:

<?xml version="1.0" encoding="utf-8"?> <set xmlns:android="http://schemas.android.com/apk/res/android"> <alpha android:fromAlpha="1.0" android:toAlpha="0.0" android:background="#000000" android:interpolator="@android:anim/linear_interpolator" android:duration="100" android:repeatMode="restart" android:repeatCount="0"/> </set> 

As you can see, it's very simple to create this animation, so if the View Animation accomplishes your goal, use it. When it doesn't meet your needs, turn to the Property Animation system. We'll demonstrate Property Animation using the new objectAnimator in the Creating a Card Flip Animation with Fragments and Creating a Zoom Animation with a Custom Transition recipes.

The A transition animation – defining scenes and applying a transition recipe will provide additional information on the Android Transition Framework, which we will use in many of the recipes.

The Interpolator is a function that defines the rate of change for an animation.

Interpolators will be mentioned in several recipes in this chapter, as well as in the previous blink example. The Interpolator defines how the transition is calculated. A Linear Interpolator will calculate the change evenly over a set duration, whereas an AccelerateInterpolator function would create faster movement for the duration. Here is the full list of Interpolators available, along with the XML identifier:

• AccelerateDecelerateInterpolator (@android:anim/accelerate_decelerate_interpolator)
• AccelerateInterpolator (@android:anim/accelerate_interpolator)
• AnticipateInterpolator (@android:anim/anticipate_interpolator)
• AnticipateOvershootInterpolator (@android:anim/anticipate_overshoot_interpolator)
• BounceInterpolator (@android:anim/bounce_interpolator)
• CycleInterpolator (@android:anim/cycle_interpolator)
• DecelerateInterpolator (@android:anim/decelerate_interpolator)
• LinearInterpolator (@android:anim/linear_interpolator)
• OvershootInterpolator (@android:anim/overshoot_interpolator)

Although animations don't generally require much memory, the graphic resources often do. Many of the images you may want to work with often exceed the available device memory. In the first recipe of this chapter, Scaling down large images to avoid Out of Memor...

Table of contents

• Title Page
• Copyright and Credits
• Dedication
• About Packt
• Contributors
• Preface
• Activities
• Layouts
• Views, Widgets, and Styles
• Menus and Action Mode
• Fragments
• Home Screen Widgets, Search, and the System UI
• Data Storage
• Alerts and Notifications
• Using the Touchscreen and Sensors
• Graphics and Animation
• A First Look at OpenGL ES
• Multimedia
• Telephony, Networks, and the Web
• Location and Using Geofencing
• Getting Your App Ready for the Play Store
• Getting Started with Kotlin
• Other Books You May Enjoy