Book Image

Android 9 Development Cookbook - Third Edition

By : Rick Boyer
Book Image

Android 9 Development Cookbook - Third Edition

By: Rick Boyer

Overview of this book

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.

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Table of Contents (24 chapters)
Title Page
Title Page
Copyright and Credits
Copyright and Credits
Dedication
Dedication
About Packt
About Packt
Contributors
Contributors
Preface
Preface
Free Chapter
1
Activities
Activities
Introduction
Declaring an activity
Starting a new activity with an intent object
Switching between activities
Passing data to another activity
Returning a result from an activity
Saving an activity's state
Storing persistent activity data
Understanding the activity life cycle
2
Layouts
Layouts
Introduction
Defining and inflating a layout
Using RelativeLayout
Using LinearLayout
Creating tables – TableLayout and GridLayout
RecyclerView replaces ListView
Changing layout properties during runtime
3
Views, Widgets, and Styles
Views, Widgets, and Styles
Introduction
Inserting a widget into a layout
Using graphics to show button state
Creating a widget at runtime
Creating a custom component
Applying a style to a View
Turning a style into a theme
Selecting a theme based on the Android version
4
Menus and Action Mode
Menus and Action Mode
Introduction
Creating an options menu
Modifying menus and menu items during runtime
Enabling Contextual Action Mode for a view
Using Contextual Batch Mode with RecyclerView
Creating a pop-up menu
5
Fragments
Fragments
Introduction
Creating and using a Fragment
Adding and removing Fragments during runtime
Passing data between Fragments
Handling the Fragment back stack
6
Home Screen Widgets, Search, and the System UI
Home Screen Widgets, Search, and the System UI
Introduction
Creating a shortcut on the Home screen
Creating a Home screen widget
Adding Search to the Action Bar
Showing your app full-screen
7
Data Storage
Data Storage
Introduction
Storing simple data
Read and write a text file to internal storage
Read and write a text file to external storage
Including resource files in your project
Creating and using an SQLite database
Accessing data in the background using a Loader
Accessing external storage with scoped directories in Android N
8
Alerts and Notifications
Alerts and Notifications
Introduction
Lights, Action, and Sound – getting the user's attention!
Creating a Toast with a custom layout
Displaying a message box with AlertDialog
Displaying a progress dialog
Lights, Action, and Sound Redux using Notifications
Creating a Media Player Notification
Making a Flashlight with a Heads-Up Notification
Notifications with Direct Reply
9
Using the Touchscreen and Sensors
Using the Touchscreen and Sensors
Introduction
Listening for click and long-press events
Recognizing tap and other common gestures
Pinch-to-zoom with multi-touch gestures
Swipe-to-Refresh
Listing available sensors – an introduction to the Android Sensor Framework
Reading sensor data – using Android Sensor Framework events
Reading device orientation
10
Graphics and Animation
Graphics and Animation
Introduction
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 animated image (GIF/WebP) with the new ImageDecoder library
Creating a circle image with the new ImageDecoder
11
A First Look at OpenGL ES
A First Look at OpenGL ES
Introduction
Setting up the OpenGL ES environment
Drawing shapes on GLSurfaceView
Applying the projection and camera view while drawing
Moving the triangle with rotation
Rotating the triangle with user input
12
Multimedia
Multimedia
Introduction
Playing sound effects with SoundPool
Playing audio with MediaPlayer
Responding to hardware media controls in your app
Taking a photo with the default camera app
Taking a picture using the Camera2 API
13
Telephony, Networks, and the Web
Telephony, Networks, and the Web
Introduction
How to make a phone call
Monitoring phone call events
How to send SMS (text) messages
Receiving SMS messages
Displaying a web page in your application
Checking online status and connection type
Phone number blocking API
14
Location and Using Geofencing
Location and Using Geofencing
Introduction
How to get the device location
Resolving problems reported with the GoogleApiClient OnConnectionFailedListener
Creating and monitoring a Geofence
15
Getting Your App Ready for the Play Store
Getting Your App Ready for the Play Store
Introduction
The Android 6.0 Runtime Permission Model
How to schedule an alarm
Receiving notification of device boot
Using the AsyncTask for background work
Adding speech recognition to your app
How to add Google sign-in to your app
16
Getting Started with Kotlin
Getting Started with Kotlin
Introduction
How to create an Android project with Kotlin
Creating a Toast in Kotlin
Runtime permission in Kotlin
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Index
Index

Using graphics to show button state

We've talked about the versatility of Android Views and how behavior and visual appearance can be customized. In this recipe, we will create a drawable state selector, which is a resource defined in XML that specifies the drawable to use based on the View's state. The most commonly used states, along with the possible values, include the following:

  • state_pressed=["true" | "false"]
  • state_focused=["true" | "false"]
  • state_selected=["true" | "false"]
  • state_checked=["true" | "false"]
  • state_enabled=["true" | "false"]

To define a state selector, create an XML file with the <selector> element, as shown:

<?xml version="1.0" encoding="utf-8"?> 
<selector xmlns:android="http://schemas.android.com/apk/res/android" > 
</selector>

Within the <selector> element, we define an <item> element to identify the drawable to be used based on the specified state(s). Here's an example <item> element using multiple states:

 <item 
    android...
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