Book Image

Android Studio 4.2 Development Essentials - Kotlin Edition

By : Neil Smyth
Book Image

Android Studio 4.2 Development Essentials - Kotlin Edition

By: Neil Smyth

Overview of this book

Android Studio is an Integrated Development Environment that is based on the JetBrains IntelliJ IDEA. It provides developers with a unique platform to design and develop Android apps using various developer tools. The new Android Studio 4.2 has an upgraded IntelliJ platform and a variety of new features designed to improve the productivity of Android app developers. Fully updated for Android Studio 4.2, the objective of this book is to help you master the skills necessary to develop Android applications using Kotlin as the programming language. This book begins by outlining the steps necessary to set up an Android development and testing environment and introduces programming in Kotlin, addressing data types, flow control, functions, lambdas, and object-oriented programming. It includes an overview of Android Studio, covering areas such as tool windows, the code editor, and the Layout Editor tool. An introduction to Android architecture is followed by an in-depth explanation of the design of Android applications and user interfaces using the Android Studio environment. Early chapters detail Android Architecture components like view models, lifecycle management, Room database access, the Database Inspector, app navigation, live data, and data binding. Advanced topics such as intents are also covered, as are touch screen handling, gesture recognition, and the recording and playback of audio. You will also explore printing, transitions, cloud-based file storage, and foldable device support. Detailed descriptions of material design concepts are provided, including the use of floating action buttons, Snackbars, tabbed interfaces, card views, navigation drawers, and collapsing toolbars. Some key features of Android Studio 4.2 and Android discussed in-depth include the Layout Editor, the ConstraintLayout and ConstraintSet classes, MotionLayout Editor, view binding, constraint chains, barriers, and direct reply notifications. Later chapters cover advanced features of Android Studio such as App links, Dynamic Delivery, the Android Studio Profiler, Gradle build configuration, and submitting apps to the Google Play Developer Console.

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Table of Contents (94 chapters)
1
1. Introduction
1. Introduction
1.1 Downloading the Code Samples
1.2 Feedback
1.3 Errata
Free Chapter
2
2. Setting up an Android Studio Development Environment
2. Setting up an Android Studio Development Environment
2.1 System Requirements
2.2 Downloading the Android Studio Package
2.3 Installing Android Studio
2.4 The Android Studio Setup Wizard
2.5 Installing Additional Android SDK Packages
2.6 Making the Android SDK Tools Command-line Accessible
2.7 Android Studio Memory Management
2.8 Updating Android Studio and the SDK
2.9 Summary
3
3. Creating an Example Android App in Android Studio
3. Creating an Example Android App in Android Studio
3.1 About the Project
3.2 Creating a New Android Project
3.3 Creating an Activity
3.4 Defining the Project and SDK Settings
3.5 Modifying the Example Application
3.6 Modifying the User Interface
3.7 Reviewing the Layout and Resource Files
3.8 Adding the Kotlin Extensions Plugin
3.9 Adding Interaction
3.10 Summary
4
4. Creating an Android Virtual Device (AVD) in Android Studio
4. Creating an Android Virtual Device (AVD) in Android Studio
4.1 About Android Virtual Devices
4.2 Creating a New AVD
4.3 Starting the Emulator
4.4 Running the Application in the AVD
4.5 Running on Multiple Devices
4.6 Stopping a Running Application
4.7 Supporting Dark Theme
4.8 Running the Emulator in a Tool Window
4.9 AVD Command-line Creation
4.10 Android Virtual Device Configuration Files
4.11 Moving and Renaming an Android Virtual Device
4.12 Summary
5
5. Using and Configuring the Android Studio AVD Emulator
5. Using and Configuring the Android Studio AVD Emulator
5.1 The Emulator Environment
5.2 The Emulator Toolbar Options
5.3 Working in Zoom Mode
5.4 Resizing the Emulator Window
5.5 Extended Control Options
5.6 Working with Snapshots
5.7 Configuring Fingerprint Emulation
5.8 The Emulator in Tool Window Mode
5.9 Summary
6
6. A Tour of the Android Studio User Interface
6. A Tour of the Android Studio User Interface
6.1 The Welcome Screen
6.2 The Main Window
6.3 The Tool Windows
6.4 Android Studio Keyboard Shortcuts
6.5 Switcher and Recent Files Navigation
6.6 Changing the Android Studio Theme
6.7 Summary
7
7. Testing Android Studio Apps on a Physical Android Device
7. Testing Android Studio Apps on a Physical Android Device
7.1 An Overview of the Android Debug Bridge (ADB)
7.2 Enabling ADB on Android based Devices
7.3 Testing the adb Connection
7.4 Summary
8
8. The Basics of the Android Studio Code Editor
8. The Basics of the Android Studio Code Editor
8.1 The Android Studio Editor
8.2 Splitting the Editor Window
8.3 Code Completion
8.4 Statement Completion
8.5 Parameter Information
8.6 Parameter Name Hints
8.7 Code Generation
8.8 Code Folding
8.9 Quick Documentation Lookup
8.10 Code Reformatting
8.11 Finding Sample Code
8.12 Live Templates
8.13 Summary
9
9. An Overview of the Android Architecture
9. An Overview of the Android Architecture
9.1 The Android Software Stack
9.2 The Linux Kernel
9.3 Android Runtime – ART
9.4 Android Libraries
9.5 Application Framework
9.6 Applications
9.7 Summary
10
10. The Anatomy of an Android Application
10. The Anatomy of an Android Application
10.1 Android Activities
10.2 Android Fragments
10.3 Android Intents
10.4 Broadcast Intents
10.5 Broadcast Receivers
10.6 Android Services
10.7 Content Providers
10.8 The Application Manifest
10.9 Application Resources
10.10 Application Context
10.11 Summary
11
11. An Introduction to Kotlin
11. An Introduction to Kotlin
11.1 What is Kotlin?
11.2 Kotlin and Java
11.3 Converting from Java to Kotlin
11.4 Kotlin and Android Studio
11.5 Experimenting with Kotlin
11.6 Semi-colons in Kotlin
11.7 Summary
12
12. Kotlin Data Types,Variables and Nullability
12. Kotlin Data Types,Variables and Nullability
12.1 Kotlin Data Types
12.2 Mutable Variables
12.3 Immutable Variables
12.4 Declaring Mutable and Immutable Variables
12.5 Data Types are Objects
12.6 Type Annotations and Type Inference
12.7 Nullable Type
12.8 The Safe Call Operator
12.9 Not-Null Assertion
12.10 Nullable Types and the let Function
12.11 Late Initialization (lateinit)
12.12 The Elvis Operator
12.13 Type Casting and Type Checking
12.14 Summary
13
13. Kotlin Operators and Expressions
13. Kotlin Operators and Expressions
13.1 Expression Syntax in Kotlin
13.2 The Basic Assignment Operator
13.3 Kotlin Arithmetic Operators
13.4 Augmented Assignment Operators
13.5 Increment and Decrement Operators
13.6 Equality Operators
13.7 Boolean Logical Operators
13.8 Range Operator
13.9 Bitwise Operators
13.10 Summary
14
14. Kotlin Flow Control
14. Kotlin Flow Control
14.1 Looping Flow Control
14.2 Conditional Flow Control
14.3 Summary
15
15. An Overview of Kotlin Functions and Lambdas
15. An Overview of Kotlin Functions and Lambdas
15.1 What is a Function?
15.2 How to Declare a Kotlin Function
15.3 Calling a Kotlin Function
15.4 Single Expression Functions
15.5 Local Functions
15.6 Handling Return Values
15.7 Declaring Default Function Parameters
15.8 Variable Number of Function Parameters
15.9 Lambda Expressions
15.10 Higher-order Functions
15.11 Summary
16
16. The Basics of Object Oriented Programming in Kotlin
16. The Basics of Object Oriented Programming in Kotlin
16.1 What is an Object?
16.2 What is a Class?
16.3 Declaring a Kotlin Class
16.4 Adding Properties to a Class
16.5 Defining Methods
16.6 Declaring and Initializing a Class Instance
16.7 Primary and Secondary Constructors
16.8 Initializer Blocks
16.9 Calling Methods and Accessing Properties
16.10 Custom Accessors
16.11 Nested and Inner Classes
16.12 Companion Objects
16.13 Summary
17
17. An Introduction to Kotlin Inheritance and Subclassing
17. An Introduction to Kotlin Inheritance and Subclassing
17.1 Inheritance, Classes and Subclasses
17.2 Subclassing Syntax
17.3 A Kotlin Inheritance Example
17.4 Extending the Functionality of a Subclass
17.5 Overriding Inherited Methods
17.6 Adding a Custom Secondary Constructor
17.7 Using the SavingsAccount Class
17.8 Summary
18
18. An Overview of Android View Binding
18. An Overview of Android View Binding
18.1 Find View by Id and Synthetic Properties
18.2 View Binding
18.3 Converting the AndroidSample project
18.4 Enabling View Binding
18.5 Using View Binding
18.6 Choosing an Option
18.7 View Binding in the Book Examples
18.8 Migrating a Project to View Binding
18.9 Summary
19
19. Understanding Android Application and Activity Lifecycles
19. Understanding Android Application and Activity Lifecycles
19.1 Android Applications and Resource Management
19.2 Android Process States
19.3 Inter-Process Dependencies
19.4 The Activity Lifecycle
19.5 The Activity Stack
19.6 Activity States
19.7 Configuration Changes
19.8 Handling State Change
19.9 Summary
20
20. Handling Android Activity State Changes
20. Handling Android Activity State Changes
20.1 New vs. Old Lifecycle Techniques
20.2 The Activity and Fragment Classes
20.3 Dynamic State vs. Persistent State
20.4 The Android Lifecycle Methods
20.5 Lifetimes
20.6 Foldable Devices and Multi-Resume
20.7 Disabling Configuration Change Restarts
20.8 Lifecycle Method Limitations
20.9 Summary
21
21. Android Activity State Changes by Example
21. Android Activity State Changes by Example
21.1 Creating the State Change Example Project
21.2 Designing the User Interface
21.3 Overriding the Activity Lifecycle Methods
21.4 Filtering the Logcat Panel
21.5 Running the Application
21.6 Experimenting with the Activity
21.7 Summary
22
22. Saving and Restoring the State of an Android Activity
22. Saving and Restoring the State of an Android Activity
22.1 Saving Dynamic State
22.2 Default Saving of User Interface State
22.3 The Bundle Class
22.4 Saving the State
22.5 Restoring the State
22.6 Testing the Application
22.7 Summary
23
23. Understanding Android Views, View Groups and Layouts
23. Understanding Android Views, View Groups and Layouts
23.1 Designing for Different Android Devices
23.2 Views and View Groups
23.3 Android Layout Managers
23.4 The View Hierarchy
23.5 Creating User Interfaces
23.6 Summary
24
24. A Guide to the Android Studio Layout Editor Tool
24. A Guide to the Android Studio Layout Editor Tool
24.1 Basic vs. Empty Activity Templates
24.2 The Android Studio Layout Editor
24.3 Design Mode
24.4 The Palette
24.5 Design Mode and Layout Views
24.6 Night Mode
24.7 Code Mode
24.8 Split Mode
24.9 Setting Attributes
24.10 Transforms
24.11 Tools Visibility Toggles
24.12 Converting Views
24.13 Displaying Sample Data
24.14 Creating a Custom Device Definition
24.15 Changing the Current Device
24.16 Layout Validation (Multi Preview)
24.17 Summary
25
25. A Guide to the Android ConstraintLayout
25. A Guide to the Android ConstraintLayout
25.1 How ConstraintLayout Works
25.2 Baseline Alignment
25.3 Configuring Widget Dimensions
25.4 Guideline Helper
25.5 Group Helper
25.6 Barrier Helper
25.7 Flow Helper
25.8 Ratios
25.9 ConstraintLayout Advantages
25.10 ConstraintLayout Availability
25.11 Summary
26
26. A Guide to Using ConstraintLayout in Android Studio
26. A Guide to Using ConstraintLayout in Android Studio
26.1 Design and Layout Views
26.2 Autoconnect Mode
26.3 Inference Mode
26.4 Manipulating Constraints Manually
26.5 Adding Constraints in the Inspector
26.6 Viewing Constraints in the Attributes Window
26.7 Deleting Constraints
26.8 Adjusting Constraint Bias
26.9 Understanding ConstraintLayout Margins
26.10 The Importance of Opposing Constraints and Bias
26.11 Configuring Widget Dimensions
26.12 Design Time Tools Positioning
26.13 Adding Guidelines
26.14 Adding Barriers
26.15 Adding a Group
26.16 Working with the Flow Helper
26.17 Widget Group Alignment and Distribution
26.18 Converting other Layouts to ConstraintLayout
26.19 Summary
27
27. Working with ConstraintLayout Chains and Ratios in Android Studio
27. Working with ConstraintLayout Chains and Ratios in Android Studio
27.1 Creating a Chain
27.2 Changing the Chain Style
27.3 Spread Inside Chain Style
27.4 Packed Chain Style
27.5 Packed Chain Style with Bias
27.6 Weighted Chain
27.7 Working with Ratios
27.8 Summary
28
28. An Android Studio Layout Editor ConstraintLayout Tutorial
28. An Android Studio Layout Editor ConstraintLayout Tutorial
28.1 An Android Studio Layout Editor Tool Example
28.2 Creating a New Activity
28.3 Preparing the Layout Editor Environment
28.4 Adding the Widgets to the User Interface
28.5 Adding the Constraints
28.6 Testing the Layout
28.7 Using the Layout Inspector
28.8 Summary
29
29. Manual XML Layout Design in Android Studio
29. Manual XML Layout Design in Android Studio
29.1 Manually Creating an XML Layout
29.2 Manual XML vs. Visual Layout Design
29.3 Summary
30
30. Managing Constraints using Constraint Sets
30. Managing Constraints using Constraint Sets
30.1 Kotlin Code vs. XML Layout Files
30.2 Creating Views
30.3 View Attributes
30.4 Constraint Sets
30.5 Summary
31
31. An Android ConstraintSet Tutorial
31. An Android ConstraintSet Tutorial
31.1 Creating the Example Project in Android Studio
31.2 Adding Views to an Activity
31.3 Setting View Attributes
31.4 Creating View IDs
31.5 Configuring the Constraint Set
31.6 Adding the EditText View
31.7 Converting Density Independent Pixels (dp) to Pixels (px)
31.8 Summary
32
32. A Guide to using Apply Changes in Android Studio
32. A Guide to using Apply Changes in Android Studio
32.1 Introducing Apply Changes
32.2 Understanding Apply Changes Options
32.3 Using Apply Changes
32.4 Configuring Apply Changes Fallback Settings
32.5 An Apply Changes Tutorial
32.6 Using Apply Code Changes
32.7 Using Apply Changes and Restart Activity
32.8 Using Run App
32.9 Summary
33
33. An Overview and Example of Android Event Handling
33. An Overview and Example of Android Event Handling
33.1 Understanding Android Events
33.2 Using the android:onClick Resource
33.3 Event Listeners and Callback Methods
33.4 An Event Handling Example
33.5 Designing the User Interface
33.6 The Event Listener and Callback Method
33.7 Consuming Events
33.8 Summary
34
34. Android Touch and Multi-touch Event Handling
34. Android Touch and Multi-touch Event Handling
34.1 Intercepting Touch Events
34.2 The MotionEvent Object
34.3 Understanding Touch Actions
34.4 Handling Multiple Touches
34.5 An Example Multi-Touch Application
34.6 Designing the Activity User Interface
34.7 Implementing the Touch Event Listener
34.8 Running the Example Application
34.9 Summary
35
35. Detecting Common Gestures Using the Android Gesture Detector Class
35. Detecting Common Gestures Using the Android Gesture Detector Class
35.1 Implementing Common Gesture Detection
35.2 Creating an Example Gesture Detection Project
35.3 Implementing the Listener Class
35.4 Creating the GestureDetectorCompat Instance
35.5 Implementing the onTouchEvent() Method
35.6 Testing the Application
35.7 Summary
36
36. Implementing Custom Gesture and Pinch Recognition on Android
36. Implementing Custom Gesture and Pinch Recognition on Android
36.1 The Android Gesture Builder Application
36.2 The GestureOverlayView Class
36.3 Detecting Gestures
36.4 Identifying Specific Gestures
36.5 Installing and Running the Gesture Builder Application
36.6 Creating a Gestures File
36.7 Creating the Example Project
36.8 Extracting the Gestures File from the SD Card
36.9 Adding the Gestures File to the Project
36.10 Designing the User Interface
36.11 Loading the Gestures File
36.12 Registering the Event Listener
36.13 Implementing the onGesturePerformed Method
36.14 Testing the Application
36.15 Configuring the GestureOverlayView
36.16 Intercepting Gestures
36.17 Detecting Pinch Gestures
36.18 A Pinch Gesture Example Project
36.19 Summary
37
37. An Introduction to Android Fragments
37. An Introduction to Android Fragments
37.1 What is a Fragment?
37.2 Creating a Fragment
37.3 Adding a Fragment to an Activity using the Layout XML File
37.4 Adding and Managing Fragments in Code
37.5 Handling Fragment Events
37.6 Implementing Fragment Communication
37.7 Summary
38
38. Using Fragments in Android Studio - An Example
38. Using Fragments in Android Studio - An Example
38.1 About the Example Fragment Application
38.2 Creating the Example Project
38.3 Creating the First Fragment Layout
38.4 Migrating a Fragment to View Binding
38.5 Adding the Second Fragment
38.6 Adding the Fragments to the Activity
38.7 Making the Toolbar Fragment Talk to the Activity
38.8 Making the Activity Talk to the Text Fragment
38.9 Testing the Application
38.10 Summary
39
39. Modern Android App Architecture with Jetpack
39. Modern Android App Architecture with Jetpack
39.1 What is Android Jetpack?
39.2 The “Old” Architecture
39.3 Modern Android Architecture
39.4 The ViewModel Component
39.5 The LiveData Component
39.6 ViewModel Saved State
39.7 LiveData and Data Binding
39.8 Android Lifecycles
39.9 Repository Modules
39.10 Summary
40
40. An Android Jetpack ViewModel Tutorial
40. An Android Jetpack ViewModel Tutorial
40.1 About the Project
40.2 Creating the ViewModel Example Project
40.3 Reviewing the Project
40.4 Designing the Fragment Layout
40.5 Implementing the View Model
40.6 Associating the Fragment with the View Model
40.7 Modifying the Fragment
40.8 Accessing the ViewModel Data
40.9 Testing the Project
40.10 Summary
41
41. An Android Jetpack LiveData Tutorial
41. An Android Jetpack LiveData Tutorial
41.1 LiveData - A Recap
41.2 Adding LiveData to the ViewModel
41.3 Implementing the Observer
41.4 Summary
42
42. An Overview of Android Jetpack Data Binding
42. An Overview of Android Jetpack Data Binding
42.1 An Overview of Data Binding
42.2 The Key Components of Data Binding
42.3 Summary
43
43. An Android Jetpack Data Binding Tutorial
43. An Android Jetpack Data Binding Tutorial
43.1 Removing the Redundant Code
43.2 Enabling Data Binding
43.3 Adding the Layout Element
43.4 Adding the Data Element to Layout File
43.5 Working with the Binding Class
43.6 Assigning the ViewModel Instance to the Data Binding Variable
43.7 Adding Binding Expressions
43.8 Adding the Conversion Method
43.9 Adding a Listener Binding
43.10 Testing the App
43.11 Summary
44
44. An Android ViewModel Saved State Tutorial
44. An Android ViewModel Saved State Tutorial
44.1 Understanding ViewModel State Saving
44.2 Implementing ViewModel State Saving
44.3 Saving and Restoring State
44.4 Adding Saved State Support to the ViewModelDemo Project
44.5 Summary
45
45. Working with Android Lifecycle-Aware Components
45. Working with Android Lifecycle-Aware Components
45.1 Lifecycle Awareness
45.2 Lifecycle Owners
45.3 Lifecycle Observers
45.4 Lifecycle States and Events
45.5 Summary
46
46. An Android Jetpack Lifecycle Awareness Tutorial
46. An Android Jetpack Lifecycle Awareness Tutorial
46.1 Creating the Example Lifecycle Project
46.2 Creating a Lifecycle Observer
46.3 Adding the Observer
46.4 Testing the Observer
46.5 Creating a Lifecycle Owner
46.6 Testing the Custom Lifecycle Owner
46.7 Summary
47
47. An Overview of the Navigation Architecture Component
47. An Overview of the Navigation Architecture Component
47.1 Understanding Navigation
47.2 Declaring a Navigation Host
47.3 The Navigation Graph
47.4 Accessing the Navigation Controller
47.5 Triggering a Navigation Action
47.6 Passing Arguments
47.7 Summary
48
48. An Android Jetpack Navigation Component Tutorial
48. An Android Jetpack Navigation Component Tutorial
48.1 Creating the NavigationDemo Project
48.2 Adding Navigation to the Build Configuration
48.3 Creating the Navigation Graph Resource File
48.4 Declaring a Navigation Host
48.5 Adding Navigation Destinations
48.6 Designing the Destination Fragment Layouts
48.7 Adding an Action to the Navigation Graph
48.8 Implement the OnFragmentInteractionListener
48.9 Adding View Binding Support to the Destination Fragments
48.10 Triggering the Action
48.11 Passing Data Using Safeargs
48.12 Summary
49
49. An Introduction to MotionLayout
49. An Introduction to MotionLayout
49.1 An Overview of MotionLayout
49.2 MotionLayout
49.3 MotionScene
49.4 Configuring ConstraintSets
49.5 Custom Attributes
49.6 Triggering an Animation
49.7 Arc Motion
49.8 Keyframes
49.9 Time Linearity
49.10 KeyTrigger
49.11 Cycle and Time Cycle Keyframes
49.12 Starting an Animation from Code
49.13 Summary
50
50. An Android MotionLayout Editor Tutorial
50. An Android MotionLayout Editor Tutorial
50.1 Creating the MotionLayoutDemo Project
50.2 ConstraintLayout to MotionLayout Conversion
50.3 Configuring Start and End Constraints
50.4 Previewing the MotionLayout Animation
50.5 Adding an OnClick Gesture
50.6 Adding an Attribute Keyframe to the Transition
50.7 Adding a CustomAttribute to a Transition
50.8 Adding Position Keyframes
50.9 Summary
51
51. A MotionLayout KeyCycle Tutorial
51. A MotionLayout KeyCycle Tutorial
51.1 An Overview of Cycle Keyframes
51.2 Using the Cycle Editor
51.3 Creating the KeyCycleDemo Project
51.4 Configuring the Start and End Constraints
51.5 Creating the Cycles
51.6 Previewing the Animation
51.7 Adding the KeyFrameSet to the MotionScene
51.8 Summary
52
52. Working with the Floating Action Button and Snackbar
52. Working with the Floating Action Button and Snackbar
52.1 The Material Design
52.2 The Design Library
52.3 The Floating Action Button (FAB)
52.4 The Snackbar
52.5 Creating the Example Project
52.6 Reviewing the Project
52.7 Removing Navigation Features
52.8 Changing the Floating Action Button
52.9 Adding an Action to the Snackbar
52.10 Summary
53
53. Creating a Tabbed Interface using the TabLayout Component
53. Creating a Tabbed Interface using the TabLayout Component
53.1 An Introduction to the ViewPager
53.2 An Overview of the TabLayout Component
53.3 Creating the TabLayoutDemo Project
53.4 Creating the First Fragment
53.5 Duplicating the Fragments
53.6 Adding the TabLayout and ViewPager
53.7 Creating the Pager Adapter
53.8 Performing the Initialization Tasks
53.9 Testing the Application
53.10 Customizing the TabLayout
53.11 Displaying Icon Tab Items
53.12 Summary
54
54. Working with the RecyclerView and CardView Widgets
54. Working with the RecyclerView and CardView Widgets
54.1 An Overview of the RecyclerView
54.2 An Overview of the CardView
54.3 Summary
55
55. An Android RecyclerView and CardView Tutorial
55. An Android RecyclerView and CardView Tutorial
55.1 Creating the CardDemo Project
55.2 Modifying the Basic Activity Project
55.3 Designing the CardView Layout
55.4 Adding the RecyclerView
55.5 Adding the Image Files
55.6 Creating the RecyclerView Adapter
55.7 Initializing the RecyclerView Component
55.8 Testing the Application
55.9 Responding to Card Selections
55.10 Summary
56
56. A Layout Editor Sample Data Tutorial
56. A Layout Editor Sample Data Tutorial
56.1 Adding Sample Data to a Project
56.2 Using Custom Sample Data
56.3 Summary
57
57. Working with the AppBar and Collapsing Toolbar Layouts
57. Working with the AppBar and Collapsing Toolbar Layouts
57.1 The Anatomy of an AppBar
57.2 The Example Project
57.3 Coordinating the RecyclerView and Toolbar
57.4 Introducing the Collapsing Toolbar Layout
57.5 Changing the Title and Scrim Color
57.6 Summary
58
58. An Android Studio Primary/Detail Flow Tutorial
58. An Android Studio Primary/Detail Flow Tutorial
58.1 The Primary/Detail Flow
58.2 Creating a Primary/Detail Flow Activity
58.3 Modifying the Primary/Detail Flow Template
58.4 Changing the Content Model
58.5 Changing the Detail Pane
58.6 Modifying the WebsiteDetailFragment Class
58.7 Modifying the WebsiteListFragment Class
58.8 Adding Manifest Permissions
58.9 Running the Application
58.10 Summary
59
59. An Overview of Android Intents
59. An Overview of Android Intents
59.1 An Overview of Intents
59.2 Explicit Intents
59.3 Returning Data from an Activity
59.4 Implicit Intents
59.5 Using Intent Filters
59.6 Checking Intent Availability
59.7 Summary
60
60. Android Explicit Intents – A Worked Example
60. Android Explicit Intents – A Worked Example
60.1 Creating the Explicit Intent Example Application
60.2 Designing the User Interface Layout for MainActivity
60.3 Creating the Second Activity Class
60.4 Designing the User Interface Layout for SecondActivity
60.5 Reviewing the Application Manifest File
60.6 Creating the Intent
60.7 Extracting Intent Data
60.8 Launching SecondActivity as a Sub-Activity
60.9 Returning Data from a Sub-Activity
60.10 Testing the Application
60.11 Summary
61
61. Android Implicit Intents – A Worked Example
61. Android Implicit Intents – A Worked Example
61.1 Creating the Android Studio Implicit Intent Example Project
61.2 Designing the User Interface
61.3 Creating the Implicit Intent
61.4 Adding a Second Matching Activity
61.5 Adding the Web View to the UI
61.6 Obtaining the Intent URL
61.7 Modifying the MyWebView Project Manifest File
61.8 Installing the MyWebView Package on a Device
61.9 Testing the Application
61.10 Summary
62
62. Android Broadcast Intents and Broadcast Receivers
62. Android Broadcast Intents and Broadcast Receivers
62.1 An Overview of Broadcast Intents
62.2 An Overview of Broadcast Receivers
62.3 Obtaining Results from a Broadcast
62.4 Sticky Broadcast Intents
62.5 The Broadcast Intent Example
62.6 Creating the Example Application
62.7 Creating and Sending the Broadcast Intent
62.8 Creating the Broadcast Receiver
62.9 Registering the Broadcast Receiver
62.10 Testing the Broadcast Example
62.11 Listening for System Broadcasts
62.12 Summary
63
63. An Introduction to Kotlin Coroutines
63. An Introduction to Kotlin Coroutines
63.1 What are Coroutines?
63.2 Threads vs Coroutines
63.3 Coroutine Scope
63.4 Suspend Functions
63.5 Coroutine Dispatchers
63.6 Coroutine Builders
63.7 Jobs
63.8 Coroutines – Suspending and Resuming
63.9 Returning Results from a Coroutine
63.10 Using withContext
63.11 Coroutine Channel Communication
63.12 Summary
64
64. An Android Kotlin Coroutines Tutorial
64. An Android Kotlin Coroutines Tutorial
64.1 Creating the Coroutine Example Application
64.2 Adding Coroutine Support to the Project
64.3 Designing the User Interface
64.4 Implementing the SeekBar
64.5 Adding the Suspend Function
64.6 Implementing the launchCoroutines Method
64.7 Testing the App
64.8 Summary
65
65. An Overview of Android Services
65. An Overview of Android Services
65.1 Started Services
65.2 Intent Service
65.3 Bound Service
65.4 The Anatomy of a Service
65.5 Controlling Destroyed Service Restart Options
65.6 Declaring a Service in the Manifest File
65.7 Starting a Service Running on System Startup
65.8 Summary
66
66. Implementing an Android Started Service – A Worked Example
66. Implementing an Android Started Service – A Worked Example
66.1 Creating the Example Project
66.2 Designing the User Interface
66.3 Creating the Service Class
66.4 Adding the Service to the Manifest File
66.5 Starting the Service
66.6 Testing the IntentService Example
66.7 Using the Service Class
66.8 Creating the New Service
66.9 Launching the Service
66.10 Running the Application
66.11 Using a Coroutine for the Service Task
66.12 Summary
67
67. Android Local Bound Services – A Worked Example
67. Android Local Bound Services – A Worked Example
67.1 Understanding Bound Services
67.2 Bound Service Interaction Options
67.3 A Local Bound Service Example
67.4 Adding a Bound Service to the Project
67.5 Implementing the Binder
67.6 Binding the Client to the Service
67.7 Completing the Example
67.8 Testing the Application
67.9 Summary
68
68. Android Remote Bound Services – A Worked Example
68. Android Remote Bound Services – A Worked Example
68.1 Client to Remote Service Communication
68.2 Creating the Example Application
68.3 Designing the User Interface
68.4 Implementing the Remote Bound Service
68.5 Configuring a Remote Service in the Manifest File
68.6 Launching and Binding to the Remote Service
68.7 Sending a Message to the Remote Service
68.8 Summary
69
69. An Android Notifications Tutorial
69. An Android Notifications Tutorial
69.1 An Overview of Notifications
69.2 Creating the NotifyDemo Project
69.3 Designing the User Interface
69.4 Creating the Second Activity
69.5 Creating a Notification Channel
69.6 Creating and Issuing a Notification
69.7 Launching an Activity from a Notification
69.8 Adding Actions to a Notification
69.9 Bundled Notifications
69.10 Summary
70
70. An Android Direct Reply Notification Tutorial
70. An Android Direct Reply Notification Tutorial
70.1 Creating the DirectReply Project
70.2 Designing the User Interface
70.3 Creating the Notification Channel
70.4 Building the RemoteInput Object
70.5 Creating the PendingIntent
70.6 Creating the Reply Action
70.7 Receiving Direct Reply Input
70.8 Updating the Notification
70.9 Summary
71
71. Foldable Devices and Multi-Window Support
71. Foldable Devices and Multi-Window Support
71.1 Foldables and Multi-Window Support
71.2 Using a Foldable Emulator
71.3 Entering Multi-Window Mode
71.4 Enabling and using Freeform Support
71.5 Checking for Freeform Support
71.6 Enabling Multi-Window Support in an App
71.7 Specifying Multi-Window Attributes
71.8 Detecting Multi-Window Mode in an Activity
71.9 Receiving Multi-Window Notifications
71.10 Launching an Activity in Multi-Window Mode
71.11 Configuring Freeform Activity Size and Position
71.12 Summary
72
72. An Overview of Android SQLite Databases
72. An Overview of Android SQLite Databases
72.1 Understanding Database Tables
72.2 Introducing Database Schema
72.3 Columns and Data Types
72.4 Database Rows
72.5 Introducing Primary Keys
72.6 What is SQLite?
72.7 Structured Query Language (SQL)
72.8 Trying SQLite on an Android Virtual Device (AVD)
72.9 The Android Room Persistence Library
72.10 Summary
73
73. The Android Room Persistence Library
73. The Android Room Persistence Library
73.1 Revisiting Modern App Architecture
73.2 Key Elements of Room Database Persistence
73.3 Understanding Entities
73.4 Data Access Objects
73.5 The Room Database
73.6 The Repository
73.7 In-Memory Databases
73.8 Database Inspector
73.9 Summary
74
74. An Android TableLayout and TableRow Tutorial
74. An Android TableLayout and TableRow Tutorial
74.1 The TableLayout and TableRow Layout Views
74.2 Creating the Room Database Project
74.3 Converting to a LinearLayout
74.4 Adding the TableLayout to the User Interface
74.5 Configuring the TableRows
74.6 Adding the Button Bar to the Layout
74.7 Adding the RecyclerView
74.8 Adjusting the Layout Margins
74.9 Summary
75
75. An Android Room Database and Repository Tutorial
75. An Android Room Database and Repository Tutorial
75.1 About the RoomDemo Project
75.2 Modifying the Build Configuration
75.3 Building the Entity
75.4 Creating the Data Access Object
75.5 Adding the Room Database
75.6 Adding the Repository
75.7 Modifying the ViewModel
75.8 Creating the Product Item Layout
75.9 Adding the RecyclerView Adapter
75.10 Preparing the Main Fragment
75.11 Adding the Button Listeners
75.12 Adding LiveData Observers
75.13 Initializing the RecyclerView
75.14 Testing the RoomDemo App
75.15 Using the Database Inspector
75.16 Summary
76
76. Accessing Cloud Storage using the Android Storage Access Framework
76. Accessing Cloud Storage using the Android Storage Access Framework
76.1 The Storage Access Framework
76.2 Working with the Storage Access Framework
76.3 Filtering Picker File Listings
76.4 Handling Intent Results
76.5 Reading the Content of a File
76.6 Writing Content to a File
76.7 Deleting a File
76.8 Gaining Persistent Access to a File
76.9 Summary
77
77. An Android Storage Access Framework Example
77. An Android Storage Access Framework Example
77.1 About the Storage Access Framework Example
77.2 Creating the Storage Access Framework Example
77.3 Designing the User Interface
77.4 Declaring Request Codes
77.5 Creating a New Storage File
77.6 The onActivityResult() Method
77.7 Saving to a Storage File
77.8 Opening and Reading a Storage File
77.9 Testing the Storage Access Application
77.10 Summary
78
78. Video Playback on Android using the VideoView and MediaController Classes
78. Video Playback on Android using the VideoView and MediaController Classes
78.1 Introducing the Android VideoView Class
78.2 Introducing the Android MediaController Class
78.3 Creating the Video Playback Example
78.4 Designing the VideoPlayer Layout
78.5 Downloading the Video File
78.6 Configuring the VideoView
78.7 Adding the MediaController to the Video View
78.8 Setting up the onPreparedListener
78.9 Summary
79
79. Android Picture-in-Picture Mode
79. Android Picture-in-Picture Mode
79.1 Picture-in-Picture Features
79.2 Enabling Picture-in-Picture Mode
79.3 Configuring Picture-in-Picture Parameters
79.4 Entering Picture-in-Picture Mode
79.5 Detecting Picture-in-Picture Mode Changes
79.6 Adding Picture-in-Picture Actions
79.7 Summary
80
80. An Android Picture-in-Picture Tutorial
80. An Android Picture-in-Picture Tutorial
80.1 Adding Picture-in-Picture Support to the Manifest
80.2 Adding a Picture-in-Picture Button
80.3 Entering Picture-in-Picture Mode
80.4 Detecting Picture-in-Picture Mode Changes
80.5 Adding a Broadcast Receiver
80.6 Adding the PiP Action
80.7 Testing the Picture-in-Picture Action
80.8 Summary
81
81. Making Runtime Permission Requests in Android
81. Making Runtime Permission Requests in Android
81.1 Understanding Normal and Dangerous Permissions
81.2 Creating the Permissions Example Project
81.3 Checking for a Permission
81.4 Requesting Permission at Runtime
81.5 Providing a Rationale for the Permission Request
81.6 Testing the Permissions App
81.7 Summary
82
82. Android Audio Recording and Playback using MediaPlayer and MediaRecorder
82. Android Audio Recording and Playback using MediaPlayer and MediaRecorder
82.1 Playing Audio
82.2 Recording Audio and Video using the MediaRecorder Class
82.3 About the Example Project
82.4 Creating the AudioApp Project
82.5 Designing the User Interface
82.6 Checking for Microphone Availability
82.7 Initializing the Activity
82.8 Implementing the recordAudio() Method
82.9 Implementing the stopAudio() Method
82.10 Implementing the playAudio() method
82.11 Configuring and Requesting Permissions
82.12 Testing the Application
82.13 Summary
83
83. Printing with the Android Printing Framework
83. Printing with the Android Printing Framework
83.1 The Android Printing Architecture
83.2 The Print Service Plugins
83.3 Google Cloud Print
83.4 Printing to Google Drive
83.5 Save as PDF
83.6 Printing from Android Devices
83.7 Options for Building Print Support into Android Apps
83.8 Summary
84
84. An Android HTML and Web Content Printing Example
84. An Android HTML and Web Content Printing Example
84.1 Creating the HTML Printing Example Application
84.2 Printing Dynamic HTML Content
84.3 Creating the Web Page Printing Example
84.4 Removing the Floating Action Button
84.5 Removing Navigation Features
84.6 Designing the User Interface Layout
84.7 Accessing the WebView from the Main Activity
84.8 Loading the Web Page into the WebView
84.9 Adding the Print Menu Option
84.10 Summary
85
85. A Guide to Android Custom Document Printing
85. A Guide to Android Custom Document Printing
85.1 An Overview of Android Custom Document Printing
85.2 Preparing the Custom Document Printing Project
85.3 Creating the Custom Print Adapter
85.4 Implementing the onLayout() Callback Method
85.5 Implementing the onWrite() Callback Method
85.6 Checking a Page is in Range
85.7 Drawing the Content on the Page Canvas
85.8 Starting the Print Job
85.9 Testing the Application
85.10 Summary
86
86. An Introduction to Android App Links
86. An Introduction to Android App Links
86.1 An Overview of Android App Links
86.2 App Link Intent Filters
86.3 Handling App Link Intents
86.4 Associating the App with a Website
86.5 Summary
87
87. An Android Studio App Links Tutorial
87. An Android Studio App Links Tutorial
87.1 About the Example App
87.2 The Database Schema
87.3 Loading and Running the Project
87.4 Adding the URL Mapping
87.5 Adding the Intent Filter
87.6 Adding Intent Handling Code
87.7 Testing the App Link
87.8 Associating an App Link with a Web Site
87.9 Summary
88
88. A Guide to the Android Studio Profiler
88. A Guide to the Android Studio Profiler
88.1 Accessing the Android Profiler
88.2 Enabling Advanced Profiling
88.3 The Android Profiler Tool Window
88.4 The Sessions Panel
88.5 The CPU Profiler
88.6 Memory Profiler
88.7 Network Profiler
88.8 Energy Profiler
88.9 Summary
89
89. An Android Biometric Authentication Tutorial
89. An Android Biometric Authentication Tutorial
89.1 An Overview of Biometric Authentication
89.2 Creating the Biometric Authentication Project
89.3 Configuring Device Fingerprint Authentication
89.4 Adding the Biometric Permission to the Manifest File
89.5 Designing the User Interface
89.6 Adding a Toast Convenience Method
89.7 Checking the Security Settings
89.8 Configuring the Authentication Callbacks
89.9 Adding the CancellationSignal
89.10 Starting the Biometric Prompt
89.11 Testing the Project
89.12 Summary
90
90. Creating, Testing and Uploading an Android App Bundle
90. Creating, Testing and Uploading an Android App Bundle
90.1 The Release Preparation Process
90.2 Android App Bundles
90.3 Register for a Google Play Developer Console Account
90.4 Configuring the App in the Console
90.5 Enabling Google Play App Signing
90.6 Creating a Keystore File
90.7 Creating the Android App Bundle
90.8 Generating Test APK Files
90.9 Uploading the App Bundle to the Google Play Developer Console
90.10 Exploring the App Bundle
90.11 Managing Testers
90.12 Rolling the App Out for Testing
90.13 Uploading New App Bundle Revisions
90.14 Analyzing the App Bundle File
90.15 Summary
91
91. An Overview of Android Dynamic Feature Modules
91. An Overview of Android Dynamic Feature Modules
91.1 An Overview of Dynamic Feature Modules
91.2 Dynamic Feature Module Architecture
91.3 Creating a Dynamic Feature Module
91.4 Converting an Existing Module for Dynamic Delivery
91.5 Working with Dynamic Feature Modules
91.6 Handling Large Dynamic Feature Modules
91.7 Summary
92
92. An Android Studio Dynamic Feature Tutorial
92. An Android Studio Dynamic Feature Tutorial
92.1 Creating the DynamicFeature Project
92.2 Adding Dynamic Feature Support to the Project
92.3 Designing the Base Activity User Interface
92.4 Adding the Dynamic Feature Module
92.5 Reviewing the Dynamic Feature Module
92.6 Adding the Dynamic Feature Activity
92.7 Implementing the launchIntent() Method
92.8 Uploading the App Bundle for Testing
92.9 Implementing the installFeature() Method
92.10 Adding the Update Listener
92.11 Handling Large Downloads
92.12 Using Deferred Installation
92.13 Removing a Dynamic Module
92.14 Summary
93
93. An Overview of Gradle in Android Studio
93. An Overview of Gradle in Android Studio
93.1 An Overview of Gradle
93.2 Gradle and Android Studio
93.3 The Top-level Gradle Build File
93.4 Module Level Gradle Build Files
93.5 Configuring Signing Settings in the Build File
93.6 Running Gradle Tasks from the Command-line
93.7 Summary
94
Index
Index

12.8 The Safe Call Operator

A nullable variable also cannot be used to call a function or to access a property in the usual way. Earlier in this chapter the toUpperCase() function was called on a String object. Given the possibility that this could cause a function to be called on a null reference, the following code will be disallowed by the compiler:

val username: String? = null

val uppercase = username.toUpperCase()

The exact error message generated by the compiler in this situation reads as follows:

Error: (Only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type String?

In this instance, the compiler is essentially refusing to allow the function call to be made because no attempt has been made to verify that the variable is non-null. One way around this is to add some code to verify that something other than null value has been assigned to the variable prior to making the function call:

if (username != null) {

  ...

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