Android development with Kotlin : learn Android application development with the extensive features of Kotlin

Custom getters/setters -- The getter versus property default value -- Late-initialized properties -- Annotating properties -- Inline properties -- Constructors -- Property versus constructor parameter -- Constructor with default arguments -- Patterns -- Inheritance -- The JvmOverloads annotation -- Interfaces -- Data classes -- The equals and hashCode method -- The toString method -- The copy method -- Destructive declarations -- Operator overloading -- Object declaration -- Object expression -- Companion objects -- Companion object instantiation -- Enum classes -- Infix calls for named methods -- Visibility modifiers -- Internal modifier and Java bytecode -- Sealed classes -- Nested classes -- Import aliases -- Summary -- Chapter 5: Functions as First-Class Citizens -- Function type -- What is function type under the hood? -- Anonymous functions -- Lambda expressions -- Implicit name of a single parameter -- Higher-order functions -- Providing operations to functions -- Observer (Listener) pattern -- Callback after a threaded operation -- Combination of named arguments and lambda expressions -- Last lambda in argument convention -- Named code surrounding -- Processing data structures using LINQ style -- Java SAM support in Kotlin -- Named Kotlin function types -- Named parameters in function type -- Type alias -- Underscore for unused variables -- Destructuring in lambda expressions -- Inline functions -- The noinline modifier -- Non-local returns -- Labeled return in lambda expressions -- Crossinline modifier -- Inline properties -- Function References -- Summary -- Chapter 6: Generics Are Your Friends -- Generics -- The need for generics -- Type parameters versus type arguments -- Generic constraints -- Nullability -- Variance -- Variance modifiers -- Use-site variance versus declaration-site variance -- Collection variance;Variance producer/consumer limitation -- Invariant constructor -- Type erasure -- Reified type parameters -- The startActivity method -- Star-projections -- Type parameter naming conventions -- Summary -- Chapter 7: Extension Functions and Properties -- Extension functions -- Extension functions under the hood -- No method overriding -- Access to receiver elements -- Extensions are resolved statically -- Companion object extensions -- Operator overloading using extension functions -- Where should top-level extension functions be used? -- Extension properties -- Where should extension properties be used? -- Member extension functions and properties -- Type of receivers -- Member extension functions and properties under the hood -- Generic extension functions -- Collection processing -- Kotlin collection type hierarchy -- The map, filter, flatMap functions -- The forEach and onEach functions -- The withIndex and indexed variants -- The sum, count, min, max, and sorted functions -- Other stream processing functions -- Examples of stream collection processing -- Sequence -- Function literals with receiver -- Kotlin standard library functions -- The let function -- Using the apply function for initialization -- The also function -- The run and with function -- The to function -- Domain-specific language -- Anko -- Summary -- Chapter 8: Delegates -- Class delegation -- Delegation pattern -- Decorator pattern -- Property delegation -- What are delegated properties? -- Predefined delegates -- The lazy function -- The notNull function -- The observable delegate -- The vetoable delegate -- Property delegation to Map type -- Custom delegates -- View binging -- Preference binding -- Providing a delegate -- Summary -- Chapter 9: Making Your Marvel Gallery Application -- Marvel Gallery -- How to use this chapter -- Make an empty project -- Character gallery;Cover -- Copyrights -- Credits -- About the Authors -- About the Reviewers -- www.PacktPub.com -- Customer Feedback -- Table of Contents -- Preface -- Chapter 1: Beginning Your Kotlin Adventure -- Say hello to Kotlin -- Awesome Kotlin examples -- Dealing with Kotlin code -- Kotlin Playground -- Android Studio -- Configuring Kotlin for the project -- Using Kotlin in a new Android project -- Java to Kotlin converter (J2K) -- Alternative ways to run Kotlin code -- Kotlin under the hood -- The Kotlin standard library -- More reasons to use Kotlin -- Summary -- Chapter 2: Laying a Foundation -- Variables -- Type inference -- Strict null safety -- Safe call -- Elvis operator -- Not null assertion -- Let -- Nullability and Java -- Casts -- Safe/unsafe cast operator -- Smart casts -- Type smart casts -- Non-nullable smart cast -- Primitive data types -- Numbers -- Char -- Arrays -- The Boolean type -- Composite data types -- Strings -- String templates -- Ranges -- Collections -- Statements versus expressions -- Control flow -- The if statement -- The when expression -- Loops -- The for loop -- The while loop -- Other iterations -- Break and continue -- Exceptions -- The try ... catch block -- Compile-time constants -- Delegates -- Summary -- Chapter 3: Playing with Functions -- Basic function declaration and usages -- Parameters -- Returning functions -- Vararg parameter -- Single-expression functions -- Tail-recursive functions -- Different ways of calling a function -- Default arguments values -- Named arguments syntax -- Top-level functions -- Top-level functions under the hood -- Local functions -- Nothing return type -- Summary -- Chapter 4: Classes and Objects -- Classes -- Class declaration -- Properties -- Read-write versus read-only property -- Property access syntax between Kotlin and Java -- Increment and decrement operators;View implementation -- Network definition -- Business logic implementation -- Putting it all together -- Character search -- Character profile display -- Summary -- Index Cover......Page 1 Copyrights......Page 3 Credits......Page 4 About the Authors......Page 5 About the Reviewers......Page 7 www.PacktPub.com......Page 8 Customer Feedback......Page 9 Table of Contents......Page 10 Preface......Page 16 Chapter 1: Beginning Your Kotlin Adventure......Page 22 Say hello to Kotlin......Page 23 Awesome Kotlin examples......Page 25 Kotlin Playground......Page 31 Configuring Kotlin for the project......Page 33 Using Kotlin in a new Android project......Page 36 Java to Kotlin converter (J2K)......Page 38 Alternative ways to run Kotlin code......Page 39 Kotlin under the hood......Page 40 More reasons to use Kotlin......Page 41 Summary......Page 43 Chapter 2: Laying a Foundation......Page 44 Variables......Page 45 Type inference......Page 47 Strict null safety......Page 51 Safe call......Page 54 Elvis operator......Page 55 Not-null assertion......Page 56 The let function......Page 57 Nullability and Java......Page 58 Safe/unsafe cast operator......Page 60 Smart casts......Page 62 Type smart casts......Page 63 Non-nullable smart cast......Page 65 Primitive data types......Page 66 Numbers......Page 67 Char......Page 69 Arrays......Page 70 The Boolean type......Page 71 String templates......Page 72 Ranges......Page 73 Statements versus expressions......Page 75 Control flow......Page 76 The if statement......Page 77 The when expression......Page 78 The for loop......Page 82 The while loop......Page 83 Break and continue......Page 84 Exceptions......Page 88 The try... catch block......Page 90 Compile-time constants......Page 91 Delegates......Page 92 Summary......Page 93 Chapter 3: Playing with Functions......Page 94 Basic function declaration and usage......Page 95 Parameters......Page 96 Returning functions......Page 98 Vararg parameter......Page 100 Single-expression functions......Page 101 Tail-recursive functions......Page 104 Default argument values......Page 106 Named arguments syntax......Page 107 Top-level functions......Page 108 Top-level functions under the hood......Page 110 Local functions......Page 112 Nothing return type......Page 114 Summary......Page 116 Chapter 4: Classes and Objects......Page 117 Properties......Page 118 Read-write versus read-only......Page 122 Property access syntax between Kotlin and Java......Page 123 Increment and decrement operators......Page 124 Custom getters/setters......Page 127 The getter versus property default value......Page 129 Late-initialized properties......Page 130 Annotating properties......Page 131 Inline properties......Page 132 Constructors......Page 133 Properties versus constructor parameters......Page 135 Patterns......Page 136 Inheritance......Page 137 The JvmOverloads annotation......Page 141 Interfaces......Page 142 Data classes......Page 146 The equals and hashCode methods......Page 147 The toString method......Page 149 The copy method......Page 150 Destructing declarations......Page 151 Operator overloading......Page 153 Object declaration......Page 156 Object expression......Page 158 Companion objects......Page 161 Companion object instantiation......Page 163 Enum classes......Page 166 Infix calls for named methods......Page 169 Visibility modifiers......Page 173 The internal modifier and Java bytecode......Page 176 Sealed classes......Page 178 Nested classes......Page 180 Import aliases......Page 181 Summary......Page 183 Chapter 5: Functions as First-Class Citizens......Page 184 Function types......Page 185 What is function type under the hood?......Page 186 Anonymous functions......Page 187 Lambda expressions......Page 189 The implicit name of a single parameter......Page 192 Higher-order functions......Page 193 Providing operations to functions......Page 195 A callback after a threaded operation......Page 196 Combination of named arguments and lambda expressions......Page 197 The last lambda in an argument convention......Page 198 Named code surrounding......Page 200 Java SAM support in Kotlin......Page 202 Named parameters in function types......Page 205 Type alias......Page 206 Underscore for unused variables......Page 209 Destructuring in lambda expressions......Page 210 Inline functions......Page 212 The noinline modifier......Page 215 Non-local returns......Page 216 Labeled returns in lambda expressions......Page 219 Crossinline modifier......Page 222 Inline properties......Page 224 Function references......Page 225 Summary......Page 228 Chapter 6: Generics Are Your Friends......Page 229 The need for generics......Page 230 Type parameters versus type arguments......Page 231 Generic constraints......Page 232 Nullability......Page 233 Variance......Page 235 Variance modifiers......Page 237 Use-site variance versus declaration-site variance......Page 239 Collection variance......Page 240 Variance producer/consumer limitation......Page 243 Type erasure......Page 245 Reified type parameters......Page 247 Star-projections......Page 249 Type parameter naming convention......Page 251 Summary......Page 252 Chapter 7: Extension Functions and Properties......Page 253 Extension functions......Page 254 Extension functions under the hood......Page 256 No method overriding......Page 257 Access to receiver elements......Page 258 Companion object extensions......Page 259 Operator overloading using extension functions......Page 260 Where should top-level extension functions be used?......Page 261 Extension properties......Page 262 Where should extension properties be used?......Page 264 Member extension functions and properties......Page 266 Types of receivers......Page 269 Member extension functions and properties under the hood......Page 271 Generic extension functions......Page 272 Collection processing......Page 274 The Kotlin collection type hierarchy......Page 276 The map, filter, and flatMap functions......Page 280 The withIndex and indexed variants......Page 282 The sum, count, min, max, and sorted functions......Page 283 Examples of stream collection processing......Page 287 Sequence......Page 290 Function literals with a receiver......Page 292 Kotlin standard library functions......Page 293 The let function......Page 295 The also function......Page 297 The run and with functions......Page 298 Domain-specific language......Page 300 Anko......Page 307 Summary......Page 308 Chapter 8: Delegates......Page 309 The Delegation pattern......Page 310 Decorator pattern......Page 316 What are delegated properties?......Page 319 The lazy function......Page 322 The notNull function......Page 328 The observable delegate......Page 330 The vetoable delegate......Page 332 Property delegation to the Map type......Page 334 Custom delegates......Page 337 View binging......Page 340 Preference binding......Page 342 Providing a delegate......Page 346 Summary......Page 348 Chapter 9: Making Your Marvel Gallery Application......Page 349 Marvel Gallery......Page 350 How to use this chapter......Page 351 Making an empty project......Page 354 Character gallery......Page 358 View implementation......Page 359 Network definition......Page 372 Business logic implementation......Page 381 Putting it all together......Page 397 Character search......Page 400 Character profile display......Page 412 Summary......Page 429 Index......Page 430 Learn how to make Android development much faster using a variety of Kotlin features, from basics to advanced, to write better quality code. About This Book • Leverage specific features of Kotlin to ease Android application development • Write code based on both object oriented and functional programming to build robust applications • Filled with various practical examples so you can easily apply your knowledge to real world scenarios • Identify the improved way of dealing with common Java patterns Who This Book Is For This book is for developers who have a basic understanding of Java language and have 6-12 months of experience with Android development and developers who feel comfortable with OOP concepts. What You Will Learn • Run a Kotlin application and understand the integration with Android Studio • Incorporate Kotlin into new/existing Android Java based project • Learn about Kotlin type system to deal with null safety and immutability • Define various types of classes and deal with properties • Define collections and transform them in functional way • Define extensions, new behaviours to existing libraries and Android framework classes • Use generic type variance modifiers to define subtyping relationship between generic types • Build a sample application In Detail Nowadays, improved application development does not just mean building better performing applications. It has become crucial to find improved ways of writing code. Kotlin is a language that helps developers build amazing Android applications easily and effectively. This book discusses Kotlin features in context of Android development. It demonstrates how common examples that are typical for Android development, can be simplified using Kotlin. It also shows all the benefits, improvements and new possibilities provided by this language. The book is divided in three modules that show the power of Kotlin and teach you how to use it properly. Each module present features in different levels of advancement. The first module covers Kotlin basics. This module will lay a firm foundation for the rest of the chapters so you are able to read and understand most of the Kotlin code. The next module dives deeper into the building blocks of Kotlin, such as functions, classes, and function types. You will learn how Kotlin brings many improvements to the table by improving common Java concepts and decreasing code verbosity. The last module presents features that are not present in Java. You will learn how certain tasks can be achieved in simpler ways thanks to Kotlin. Through the book, you will learn how to use Kotlin for Android development. You will get to know and understand most important Kotlin features, and how they can be used. You will be ready to start your own adventure with Android development with Kotlin. Style and approach A step-by-step guide that is filled with numerous real-world examples.