Flutter App Development: How to write for IOS and Android at once

Worldwide Praise for Flutter App Development: How to Write for iOS and Android at Once....5

Table of Contents....7

About the Author....16

About the Technical Reviewer....17

Who Is This Book For?....18

Foreword....23

Preface....25

Chapter 1: Hello Flutter....27

What Is Flutter?....28

Why Flutter?....29

The Other Options....30

Native Solutions....31

Conclusion....32

Chapter 2: Developing in Flutter....33

The Flutter Toolchain....34

The Flutter SDK....34

Installing the Flutter SDK....34

IDEs....34

VS Code from Microsoft....35

Android Studio/IntelliJ from JetBrains....35

Which IDE Should I Use?....35

IDE DevTools....36

Emulators....37

iOS Simulator....37

Android Emulator....38

Keeping the Tools Up to Date....39

Flutter doctor....40

Flutter Upgrade....41

The Flutter Development Process....42

Scaffolding the App and Files....43

Anatomy of a Flutter Project....43

Running Your App....45

Running It As a Web App....46

Running It on a Tethered Device....47

Hot Reloading....47

Debugging....48

Conclusion....49

Chapter 3: Everything Is Widgets....50

UI As Code....53

Built-In Flutter Widgets....54

Value Widgets....55

Layout Widgets....56

Navigation Widgets....56

Other Widgets....57

How to Create Your Own Stateless Widgets....57

Widgets Have Keys....61

Passing a Value into Your Widget....62

Stateless and Stateful Widgets....64

So Which One Should I Create?....64

Conclusion....65

Chapter 4: Value Widgets....66

The Text Widget....66

The Icon Widget....67

The Image Widget....69

Embedded Images....70

Network Images....71

Sizing an Image....71

SnackBar Widget....74

Input Widgets....76

Text Fields....77

Making Your TextField Fancy....77

Password Boxes....78

Adjusting the Soft Keyboard....79

Restricting the Data That Can Be Typed....80

Checkboxes....81

Radio Buttons....82

Sliders....84

Dropdowns....85

Putting the Form Widgets Together....87

Form Widget....87

FormField Widget....89

TextFormField and DropdownButtonFormField....90

onSaved....91

validator....91

Submitting the Form....92

One Big Form Example....93

Conclusion....93

Chapter 5: Responding to Gestures....94

Meet the Button Family....95

ElevatedButton....97

TextButton and IconButton....97

FloatingActionButton (FAB)....97

SegmentedButton....98

CupertinoButton....99

Dismissible....99

Custom Gestures for Your Custom Widgets....100

Step 1: Decide on Your Gestures and Behaviors....101

Step 2: Create Your Custom Widget....101

Step 3: Add a GestureDetector widget....102

Step 4: Associate Your Gesture with Its Behavior....103

Example 1: Reacting to a Long Press....103

Example 2: Pinching to Add a New Item....105

Example 3: Swiping Left or Right....106

Conclusion....108

Chapter 6: Navigation and Routing....109

Stack Navigation....110

Navigating Forward and Back....111

Using Anonymous Routes....112

Get Result After a Scene Is Closed....113

Drawer Navigation....114

The Drawer Widget....115

Filling the Drawer....117

Tab Navigation....119

DefaultTabController....120

TabBarView....121

TabBar and Tabs....121

TabBar at the Bottom....122

The Dialog Widget....123

showDialog() and AlertDialog....124

Responses with a Dialog....125

Navigation Methods Can Be Combined....126

Chapter 7: Managing State....128

What Is State?....128

The Shape of a StatefulWidget....130

The Most Important Rule About State!....131

Passing State Down....132

Lifting State Back Up....133

An Example of State Management....135

When Should We Use State?....139

Conclusion....141

Chapter 8: State Management Libraries....142

The InheritedWidget....142

The BLoC Pattern....143

Some Libraries....144

ScopedModel....144

Redux and Hooks....145

Provider....145

Whoa! That’s a Lot of Packages!....145

Raw State....146

Riverpod....147

1. Install flutter_riverpod....148

2. Wrap Your App with a ProviderScope....148

3. Write a Provider....149

Wait, What Is This Provider You Speak Of?....149

4. Inherit from ConsumerStateWidget....149

5. Read Data with ref.watch()....150

6. Write Data with ref.read()....151

Conclusion....151

Chapter 9: Making RESTful API Calls with HTTP....152

What Is an API Call?....153

The Flavors of API Requests....154

Making an HTTP GET or DELETE Request....155

Making an HTTP PUT, POST, or PATCH Request....157

HTTP Responses to Widgets....158

Brute Force – The Easy Way....158

FutureBuilder – The Clean Way....159

StreamBuilder....161

Strongly Typed Classes....163

Create a Business Class....163

Write a .fromJSON() Method....164

Use .fromJSON() to Hydrate the Object....164

One Big Example....165

Overview of the App....166

Create the Flutter App....168

Making a Strongly Typed Business Class....169

list_people.dart....170

A GET Request in Flutter....173

A DELETE Request in Flutter....173

upsert_person.dart....174

A POST and PUT Request in Flutter....175

Conclusion....176

Chapter 10: Styling with Themes....177

Thinking in Flutter Styles....177

Individual Styles....178

Styling Text....178

Mass-Changing Values....180

Themes....181

1. ColorScheme....182

2. TextTheme....186

3. Widget-Specific Themes....188

4. Put Them Together in a Theme....189

5. Override the Styles on Individual Widgets....190

Final Styling Thoughts....191

A Word About Colors....191

Custom Fonts....193

Conclusion....196

Chapter 11: Laying Out Your Widgets....198

Our Approach....198

1. Layout the Entire Screen (a.k.a. Scene)....199

2. Position Widgets Above and Below Each Other or Side by Side....199

3. Handle Situations When We Run Out of Space and Overflow the Scene....201

4. Handle Extra Space in the Scene....201

5. Make Finer Adjustments in Positioning....202

Laying Out the Whole Scene....202

MaterialApp Widget....203

The Scaffold Widget....204

The AppBar Widget....206

SafeArea Widget....207

Flutter’s Layout Algorithm....208

The Dreaded “Unbounded Height” Error....208

The Algorithm Itself....212

Conclusion....215

Chapter 12: Layout – Positioning Widgets....216

Putting Widgets Next to or Below Others....216

Responsive Design....218

Responsive Design in Flutter....218

Flex and MediaQuery....219

Conclusion....220

Chapter 13: Layout – Fixing Overflows....221

Overflow Warning Bars....221

Our Options to Correct Overflows....222

A Sample Problem to Solve....223

1. Allow the Children to Wrap....225

2. Squeeze the Children Until They Fit....226

3. Allow the User to Scroll....228

SingleChildScrollView Widget....229

The ListView Widget....231

ListView Is Memory Efficient....231

ListView Is Very Flexible....232

Regular ListView....233

ListView.builder: When You’re Building Widgets from a List of Objects....233

GridView Widget....234

GridView.extent()....235

GridView.count()....236

Conclusion....238

Chapter 14: Layout – Filling Extra Space....239

What if There’s Extra Space Left Over?....240

mainAxisAlignment....240

crossAxisAlignment....242

IntrinsicWidth....243

Expanded Widget....244

Open Space with Expandeds....247

Conclusion....248

Chapter 15: Layout – Fine-Tuning Positioning....249

Container Widget and the Box Model....250

EdgeInsets for Padding and Margin....251

Alignment and Positioning Within a Container....252

Container Sizes Are Not Obvious....254

Container Decorations....256

Border....259

BorderRadius....260

BoxShape....262

Conclusion....264

Chapter 16: Layout – Special Presentation Widgets....265

Slivers....265

Stack Widget....266

Positioned Widget....268

Card Widget....270

The Table Widget....271

Conclusion....274

Appendix A: Dart Language Overview....275

What Is Dart?....275

Expected Features – Dart Cheat Sheet....276

Data Types....276

Arrays/Lists....277

Conditional Expressions....277

Looping....278

Classes....278

Class Constructors....279

Unexpected Things About Dart....279

Type Inference....279

final vs. const....280

Null Safety....281

String interpolationwith $....282

Multiline Strings....282

Spread Operator....283

Map....283

Functions Are Objects....283

Big Arrow/Fat Arrow/Lambda....284

Named Function Parameters....284

Omitting “new” and “this.”....285

Class Constructor Parameter Shorthand....286

Private Class Members....287

Mixins....287

The Cascade Operator (..)....288

No Overloading....289

Named Constructors....289

Appendix B: Futures, Async, and Await....291

Flutter Apps Use an Event Loop....291

Why Would It Wait?....292

How Do We Get the Data from a Future?....293

Await....294

Async....295

Summary....296

Appendix C: Including Packages in Your Flutter App....297

Finding a Library to Use....297

Downloading the Library....299

The pubspec.yaml File....300

Using These Packages in Your Code....301

Keeping Your Packages Current....302

How to Upload Your Own Library....303

Appendix D: How to Work with Files....306

Including a File with Your App....307

Writing a File....308

And Reading It!....309

Using JSON....310

Writing Your App’s Memory to JSON....311

Reading JSON into Your App’s Memory....312

Shared Preferences....313

To Write Preferences....314

To Read Preferences....314

Conclusion....315

Appendix E: How to Debug Your Layout....316

Index....320

Create apps for iOS and Android phones and tablets using Flutter, a Google framework that produces two outputs for a single app. Let’s face it, creating iOS apps using Apple tools such as Swift and Xcode is extremely complicated. Creating Android apps with Kotlin and Android Studio is just as difficult. This book breaks down complex concepts and tasks into easily digestible segments with examples, full-color pictures, and hands-on labs with starters and solutions.As you work through the accompanying lab exercises, you’ll learn the Dart programming language; the entire Flutter development toolchain; the differences between stateful and stateless widgets; and a working knowledge of the architecture of apps. You’ll work with themes and styles, develop custom widgets, and even teach your app to respond to gestures like taps, swipes, and pinches. You’ll also design, create, and control the layout of your app. Create tools to handle form data entry from users. And ultimately create killer multiscreen apps with navigation, menus, and tabs.You’ll see that with Flutter, you can write an app one time that produces two outputs: one that can be submitted to the Apple App Store and another that can be uploaded to the Google Play Store. In short, one code creates the same app that runs on iPhones, iPads, Android phones and tablets, virtually all devices. And if you like, it can also create a version that runs on Macs, Windows, Linux, and in browsers!Flutter App Development explains difficult topics in plain, everyday terms that simplify the process of writing mobile apps.

What You’ll Learn

• Get the most out of great Flutter widgets
• Create custom widgets, both stateless and stateful
• Exercise expert control over your Flutter layouts
• Manage data in stateful widgets and with libraries like Riverpod
• Exchange data actively with RESTful API servers

Who This Book Is For

Developers who have coded in JavaScript, Python, Java, C#, C++, or any similar language. Managers, product owners, and business analysts who need to understand Flutter’s capabilities.