Kotlin for Android

A talk presented at GDG Uyo meetup on January 20th 2018 on the basic features of Kotlin in Android development.

Transcript

1. Idorenyin Obong For Android
2. Background of Kotlin
3. • Developed by JetBrains JetBrains is a software development company whose tools are targeted towards software developers and project managers
4. • Runs on JVM . JVM - Java virtual machine is an abstract computing machine that enables a computer to run a Java program.
5. • It is open source - first commit on the project was in 2010 (https://github.com/JetBrains/kotlin)
6. • It interoperates with Java
7. • It can be compiled to Javascript
8. Key features of Kotlin
9. 1. No “new” keyword // Java ArrayList<String> arrayList = new ArrayList<>();
10. 1. No “new” keyword // Java ArrayList<String> arrayList = new ArrayList<>(); // Kotlin var arrayList: ArrayList<String> = ArrayList()
11. 2. Smart inference just like JavaScript !
12. 2. Smart inference just like JavaScript ! // Java String string = "Hello world";
13. 2. Smart inference just like JavaScript ! // Java String string = "Hello world"; // Kotlin var arrayList = "Hello world"
14. 3. Null safety
15. 3. Null safety // Java - no compiler error String h = null;
16. 3. Null safety // Java - no compiler error String h = null; // Kotlin - compiler error var h:String = null
17. 3. Null safety // Kotlin - no compiler error var h:String? = null
18. 3. Null safety // Kotlin - no compiler error var h:String? = null // Kotlin - compiler error on line 2 var h:String? = null var idee = h.length
19. 3. Null safety // Kotlin - no compiler error var h:String? = null // Kotlin - compiler error on line 2 var h:String? = null var idee = h.length // no compiler error var idee = h!!.length
20. 3. Null safety - class variables // Kotlin - no compiler error lateinit var h:String
21. 4. Mutability & Immutability // Java public final String variable ="Hello";
22. 4. Mutability & Immutability // Kotlin - cannot be reassignable val variable1 = "Hello"
23. 4. Mutability & Immutability // Kotlin - cannot be reassignable val variable1 = "Hello" // Kotlin - can be reassignable var variable2 = "World"
24. // Java public class Model { String name; public String getName() { return name; } public void setName(String name) { this.name = name; } } 5. Data classes
25. // Java public class Model { String name; public String getName() { return name; } public void setName(String name) { this.name = name; } } // Kotlin data class Model(var name: String, var age: Int) 5. Data classes
26. 6. View binding
27. 6. View binding // Java @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); RecyclerView recyclerView = findViewById(R.id.recycler_view); }
28. 6. View binding // Kotlin app-module build.gradle file: apply plugin: 'kotlin-android-extensions'
29. 6. View binding // Kotlin app-module build.gradle file: apply plugin: 'kotlin-android-extensions' // Kotlin MainActivity.kt file: import kotlinx.android.synthetic.main.activity_main.* class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) recycler_view.adapter = adapter } }
30. Creating a new Kotlin Android project
38. Thank you! https://speakerdeck.com/kingidee @kingidee @kingidee