Kotlin for Android

A quick introduction to some of the cool features of Kotlin and the adoption in Android.

This has been presented at Berlin during the yearly ezhome Engineering Meetup.

Transcript

1. Kotlin for Android Spiros I. Economakis
2. Statically typed programming language for modern multiplatform applications 100% interoperable with Java™ and Android™
4. Syntax variables
5. Syntax functions
6. Syntax classes
7. Kotlin awesome features String templates Null-safety Smart casts Lambda expressions + Inline functions Extension functions Properties Primary constructors First-class delegation Type inference Declaration-site variance & Type projections Range expressions Operator overloading Companion objects Data classes Separate interfaces for read-only and mutable collections Coroutines Singletons
8. String templates
9. Smart Casts
10. Null-Safety
11. Operator Overloading
12. Primary Constructors
13. Declaration-site variance
14. Optional Arguments in Constructors
15. Data Classes
16. Singleton
17. First-class Delegation
18. First-class Delegation
19. First Class Support for Android
20. Why Kotlin for Android? Stuck on Java 6: - No javax.time - No streams - No lambdas, method refs, non-capturing anon classes - No try-with resources
21. Why Kotlin for Android? Stuck on Java 6: - No javax.time Use ThreeTenBP - No streams Use RxJava - No lambdas, method refs, non-capturing anon classes Use Retrolambda - No try-with resources Use Retrolambda or minSDK=19
22. Why Kotlin for Android? Java language restriction and problems: - Unable to add methods to platform types - Nullability problems - Mutability problems - General verbosity for common things
23. Why Kotlin for Android? Android API design problems: - Too much Inheritance - Nullability everywhere - Bunch of APIs
24. Kotlin for Android
25. Android boilerplate public class TestActivity extends AppCompatActivity { @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_welcome); ViewPager viewPager = (ViewPager) findViewById(R.id.welcomeViewPager); CircleIndicator circleIndicator = (CircleIndicator) findViewById(R.id.welcomeCircleIndicator); } }
26. Android boilerplate public class TestActivity extends AppCompatActivity { @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_welcome); ViewPager viewPager = (ViewPager) findViewById(R.id.welcomeViewPager); CircleIndicator circleIndicator = (CircleIndicator) findViewById(R.id.welcomeCircleIndicator); } }
27. Android boilerplate public class TestActivity extends AppCompatActivity { @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_welcome); ViewPager viewPager = (ViewPager) findViewById(R.id.welcomeViewPager); CircleIndicator circleIndicator = (CircleIndicator) findViewById(R.id.welcomeCircleIndicator); } }
28. Android boilerplate public class TestActivity extends AppCompatActivity { @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_welcome); ViewPager viewPager = (ViewPager) findViewById(R.id.welcomeViewPager); CircleIndicator circleIndicator = (CircleIndicator) findViewById(R.id.welcomeCircleIndicator); } }
29. Android boilerplate + Butterknife public class TestActivity extends AppCompatActivity { @BindView(R.id.welcomeViewPager) ViewPager welcomeViewPager; @BindView(R.id.welcomeCircleIndicator) CircleIndicator welcomeCircleIndicator; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.fragment_welcome); } }
30. Kotlin Android Extensions plugin What is it? Provides reference to all layout views (which have IDs) with single line of code How? Adds a hidden caching function and a field inside each Kotlin Activity
31. Kotlin Android Extensions plugin import kotlinx.android.synthetic.main.activity_welcome.* class TestActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_welcome) welcomeViewPager.setText("Hello, world!") } }
32. Kotlin Android Extensions plugin import kotlinx.android.synthetic.main.activity_welcome.* class TestActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_welcome) welcomeViewPager.setText("Hello, world!") } }
33. Kotlin Android Extensions plugin import kotlinx.android.synthetic.main.activity_welcome.* class TestActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_welcome) welcomeViewPager.setText("Hello, world!") } }
34. Kotlin & Java 100% Interoperability BUT………..
35. Kotlin & Java MULTIPLE LANGUAGES IN A PROJECT DIFFERENT LANGUAGES PARADIGMS COMPLEXITY ONBOARDING MAY LEAD TO INTEROPERABILITY BOILERPLATE ISOLATE CODE PER FEATURE/LAYER
37. Thanks Questions???