Android City-The walls of Kotlin Street

Time constraint and productivity are two major things kept in mind when working on any Android project, which could not be easily achieved by the boilerplate code and innumerable exception handlers in Java. Thus, it was time to introduce a new and more mature language, Kotlin

Transcript

1. Android City-The walls of Kotlin Street
2. Signs on the Street of Kotlin! 2 What are these “!!”? Why is my code littered with “?” and “:”?
3. HELLO! I am Temidayo Adefioye I am here because I love to talk about technology. You can find me at @temidjoy 3 https://medium.com/@temidjoy Geek Of Thrones
4. 1. Why you need Kotlin? Let’s get started...
5. “Kotlin is a statically typed programming language that runs on the Java virtual machine(JVM) and also can be compiled to Js source code. Its primary development is from a team of JetBrains Developers based in Russia 5
6. Kotlin vs Java ▪ Java is obsolete...very obsolete ▪ Verbosity and ceremony ▪ Java is vulnerable to error ▪ Goodbye to NullPointerExceptions ▪ Write less code, be happy ▪ Kotlin interoperability with Java is 100% Kotlin can help make your developer life a lot more easier! 6
7. The Walls of Kotlin Street Let’s dive into the awesomeness of Kotlin 7
8. Extension Methods 8 A handy way of extending existing classes with a new functionality without using inheritance or any forms of the Decorator patterns Java Code String escaped = escapeStringForXml(input ); Kotlin Code val escaped = input.escapeForXml()
9. Extension Methods 9 Context Adjusting Extension Methods val name = maybeGetName() val uppercase = name?.let { n -> n.toUpperCase() } Custom Extension Method fun String.escapeForXml() : String { return this .replace("&", "&amp;") .replace("<", "&lt;") .replace(">", "&gt;") } Generic Extension Methods fun <T> T.concatAsString(b: T) : String { return this.toString() + b.toString() }
10. LAMBDAS A function that is not declared, but passed immediately as an expression. 10
11. Lambdas Expression Syntax 11 //Create function fun saySomething(name: String, f: (String) -> Unit) { f(name) } //Call function saySomething("Kotlin", {name -> println("Hello $name")}) - A lambda expression is always surrounded by curly braces. - Parameter declarations in the full syntactic form go inside curly braces and have optional type annotations - The body goes after an -> sign. - If the inferred return type of the lambda is not Unit, the last (or possibly single) expression inside the lambda body is treated as the return value.
12. NULL IS SAFETY Kotlin is null-safe!!! 12
13. Null Safety 13 var artist: Artist? = null var notNullArtist: Artist = null artist?.print() artist.print() if (artist != null) { artist.print() }// Use Elvis operator to give an alternative in case the object is null val name = artist?.name ?: “empty” // Only use it when we are sure it ́s not null. // Will throw an exception otherwise. artist!!.print()
14. DATA CLASSES Classes hold nothing but data 14
15. class Hello : Greeting { private val greeting: String = “hello” override fun greet() { print(greeting) } } 15 Data Classes
16. Why do I care much about Kotlin? It’s safer I can write more productive code! Concise and Readable 16 I can Leverage Java’s rich ecosystem and JVM platform
17. ANDROID PROJECT Simple login app written in kotlin Place your screenshot here 17
18. email_sign_in_button.setOnCli ckListener { attemptLogin() } 18 Kotlin Button email_sign_in_button=(Button )findViewById(R.id.email_sign _in_button); email_sign_in_button.setOnCli ckListener { attemptLogin() } Java
19. val emailStr = email.text.toString() val passwordStr = password.text.toString() 19 Kotlin EditText email=(EditText)findViewById( R.id.email); EditText password=(EditText)findView ById(R.id.password); Java
20. private fun isEmailValid(email: String): Boolean { return email.contains("@") } 20 Kotlin private boolean isEmailValid(String email){ return email.contains("@") } Java
21. Project Source To see the entire source code for this kotlin project ▪ https://github.com/Temidtech/SimpleLoginKotlin 21
22. THANKS! Any questions? You can find me at: @temidjoy temidjoy@hotmail.com 22