Kotlin in 2 Days

K O T L I N F O R A
N D R O I D B E I N G K O T L I N E R S

@werockstar facebook: @werockstar github: @werockstar medium: @werockstar Software Developer

@werockstar W h a t i s K o t
l i n ?

@werockstar Kotlin is a statically typed programming language By Jetbrains
Kotlin supports both object-oriented and functional programming styles

@werockstar W h y K o t l i n
?

@werockstar

@werockstar Standalone compiler Source: https://kotlinlang.org/docs/tutorials/command-line.html

@werockstar ⭐

@werockstar W h y y o u s h o
u l d s t a r t u s i n g K o t l i n f o r A n d ro i d t o d a y

@werockstar 1. Language and environment are mature (Production ready) 2.
It makes Android development much easier 3. Seamlessly with IDE (Mature language with great IDE) 4. Modern language feature 5. From Startup to Fortune 500 already used in production 6. Kotlin is Multiplatform 7. Work very well with Java code base or Java libraries 8. Google fully support Source: https://antonioleiva.com/reasons-kotlin-android/

@werockstar Ofﬁcially language for android #io2017

@werockstar T h e s t a t e o
f K o t l i n

@werockstar Source: https://www.jetbrains.com/research/devecosystem-2018/kotlin/

@werockstar Null safety is a favorite feature for everyone who
ever had a NullPointerException in Java - i.e. every Android developer . Source: https://pusher.com/state-of-kotlin#kotlinverse

@werockstar K o t l i n a d o
p t i o n

@werockstar K o t l i n 1 . 3

@werockstar

@werockstar ~2011 Anywhere Java runs

@werockstar ~2018

@werockstar L a n g u a g e 1
0 1

@werockstar Ty p e I n f e re n
c e You don’t even have to declare the type

@werockstar Va r i a b l e Immutable or
not Prefer to immutable String java = "Java Language" Java , Kotlin val kotlin = "Kotlin Language" ⭐ By default, you should strive to declare all variables in Kotlin with the val keyword

@werockstar S t r i n g Te m p
l a t e

@werockstar C o n t ro l F l o
w when (with argument, without argument) and combine multiple values in the same branch if-else, if-else-if

@werockstar C o n c e p t s o
f r a n g e s L o o p +

@werockstar B a s i c F u n c
t i o n Start with fun

@werockstar 1. Block body 2. Expression body

@werockstar O b j e c t k e y
w o rd o b j e c t d e c l a r a t i o n ( s i n g l e t o n l i k e s t a t i c ) c o m p a n i o n o b j e c t s o b j e c t e x p re s s i o n ( a n a l o g o u s t o J a v a a n o n y m o u s c l a s s e s )

@werockstar C l a s s

@werockstar Java Kotlin ⭐ C o n t a i
n i n g o n l y d a t a b u t n o c o d e a re o f t e n c a l l e d v a l u e o b j e c t s

@werockstar C o n s t r u c t
o r -

@werockstar G e t t e r / S e
t t e r

@werockstar V i s i b i l i t
y m o d i f i e r Modiﬁer Class Member Top-Level Declaration Public (Default) Visible Everywhere Visible Everywhere Internal Visible In a Module Visible in a Module Protected Visible in Subclasses -- Private Visible in a Class Visible in a File

@werockstar D a t a C l a s s

@werockstar I n h e r i t a n
c e o r I m p l e m e n t K o t l i n u s e s t h e c o l o n ` : ` a f t e r t h e c l a s s n a m e t o re p l a c e b o t h t h e e x t e n d s a n d i m p l e m e n t s k e y w o rd s u s e d i n J a v a

E F F E C T I V E J
AVA B Y J O S H U A B L O C H ( A D D I S O N - W E S L E Y, 2 0 0 8 ) Design and document for inheritance or else prohibit it

@werockstar I n h e r i t a n
c e I n J a v a , O p e n b y d e f a u l t I n K o t l i n , F i n a l b y d e f a u l t

@werockstar A c c e s s m o d
i f i e r i n a c l a s s Modiﬁer Corresponding Member Comments Final Can’t Be Overridden Used By Default For Class Members Open Can Be Overridden Should Be Specified Explicitly Abstract Must Be Overridden Can Be Used Only In Abstract Classes; Abstract Members Can’t Have An Implementation Override Overrides A Member In A Superclass Or Interface Overridden Member Is Open By Default, If Not Marked Final

@werockstar O v e r r i d e @
O v e r r i d e a n n o t a t i o n i n J a v a , I n K o t l i n u s e o v e r r i d e

@werockstar O p e n C l a s s
( f i n a l b y d e f a u l t )

@werockstar A b s t r a c t C
l a s s

@werockstar O p e n v s A b s
t r a c t Open: Final by default Abstract: Open by default

@werockstar I n t e r f a c e
Similar interface in Java 8 (default methods implementation)

@werockstar D e f a u l t i m
p l e m e n t a t i o n i n I n t e r f a c e In Java 8, Mark with the default keyword In Kotlin, You just provide a method body

0 2 . 1 + Te s t i n g ✅

@werockstar U n i t Te s t i n
g i n K o t l i n

@werockstar M o c k i n g d e
p e n d e n c y i n K o t l i n

0 2 . 2

@werockstar K o t l i n ❤ J a
v a 100% compatibility

@werockstar C o d e C o n v e
n t i o n ? For example, PersonJava class

@werockstar Wo r k i n g w i t
h J a v a ☕

@werockstar K o t l i n t e l
l t o J a v a

@werockstar J a v a t e l l t
o K o t l i n

@werockstar C o n v e r t J a
v a t o K o t l i n w i t h I D E 1. Copy and past to automatic convert 2. Convert by shortcut

@werockstar P l a t f o r m Ty
p e s

@werockstar H o w t o d e a l
w i t h P l a t f o r m Ty p e s Option 1: If we have control over the java code Option 2: If we don’t have control over the java code

0 3 5

@werockstar I n i t i a l i z
e r b l o c k s The primary constructor cannot contain any code

@werockstar l a z y v s l a t
e i n i t i n i t i a l i z a t i o n

@werockstar N u l l S a f e t
y a n d h o w t o d e a l w i t h 1. let 2. ? ⛑ 3. !! 4. ?: 5. as? ☢

@werockstar D S L ( i n f i x
)

@werockstar S m a r t C a s t
Combine a type check and a cast into one operation

@werockstar C o l l e c t i o
n s Immutable Mutable K o t l i n u s e s t h e s t a n d a rd J a v a c o l l e c t i o n c l a s s e s ✅ println(<collection>.javaClass)

@werockstar C o l l e c t i o
n o p e r a t i o n s ⮑ Filter, Map, FlatMap

@werockstar Ty p e a l i a s e
s

@werockstar D e c o n s t r u
c t i n g v a l u e Unpack a single composite value into multiple variables

@werockstar H i g h e r o rd e
r f u n c t i o n ⮑ A higher order function is a function that accepts or return another function

@werockstar E x t e n s i o n
f u n c t i o n Ability to extend a class with new functionality without having to inherit from the class or use any type of design pattern such as Decorator Source: https://kotlinlang.org/docs/reference/extensions.html

@werockstar I n l i n e f u n
c t i o n I n l i n i n g i s a n a t t e m p t t o re m o v e ( o r re d u c e ) t h e r u n t i m e o v e r h e a d o f l a m b d a f u n c t i o n s b y m o v i n g ( o r i n l i n i n g ) t h e h i g h e r o rd e r f u n c t i o n a n d i t s l a m b d a a rg u m e n t b o d y t o t h e c a l l - s i t e S o u rc e : h t t p s : / / m e d i u m . c o m / t o m p e e / i d i o m a t i c - k o t l i n - i n l i n e - f u n c t i o n s - e 3 9 b 2 f 9 0 a 2 9 1

@werockstar B y t e s C o d e
V i e w e r ( I n l i n e )

0 1

@werockstar

@werockstar E n u m C l a s s

@werockstar S e a l e d C l a
s s

@werockstar D e l e g a t i o
n

@werockstar A n d r o i d F r
a m e w o r k U s e c a s e

@werockstar R x J a v a ( R x
K o t l i n ) i n A n d ro i d ? Work with UI thread

@werockstar C o ro u t i n e s
i n A n d ro i d ? Work with UI thread

@werockstar S a y g o o d b y
e f i n d V i e w B y I d W i t h A n d ro i d K o t l i n E x t e n s i o n ✋

@werockstar C a c h i n g b i
n d V i e w

@werockstar B y t e s C o d e
V i e w e r

@werockstar C o m m u n i c a
t e w i t h a c t i v i t y

@werockstar C o m m u n i c a
t e w i t h f r a g m e n t

@werockstar P l a t f o r m t
y p e s f ro m A n d ro i d S D K

@werockstar K T X

@werockstar P a rc e l a b l e

@werockstar A n d ro i d P ro j
e c t S t r u c t u re ( S u g g e s t i o n )

@werockstar

@werockstar ➕

@werockstar Build Pipeline

@werockstar U I Te s t i n g w
i t h E s p re s s o

@werockstar E s p re s s o I d
l i n g re s o u rc e

@werockstar I d l i n g re s o
u rc e o n N e t w o r k i n g

@werockstar M o c k We b S e r
v e r ( S w a p w i t h m a n u a l )

@werockstar M o c k We b S e r
v e r ( S w a p w i t h D I ? )

@werockstar R o b o t P a t t
e r n

@werockstar R o b o t P a t t
e r n ( S e p a r a t i n g t h e W h a t F ro m t h e H o w ) Source: https://speakerdeck.com/jakewharton/testing-robots-kotlin-night-may-2016 Page Object?

@werockstar

@werockstar 1 2

@werockstar

@werockstar S p o o n

@werockstar A r c h i t e c t
u r e 1. MVP 2. MVVM 3. UI Testing 4. Robot Pattern

@werockstar R e s o u r c e s
1. Kotlin in Action (Book) 2. Kotlin for Android Developers (Book) 3. Kotlin official document 4. Android Developer Google official document

@werockstar Q & A facebook: @werockstar github: @werockstar medium: @werockstar

Kotlin in 2 Days

Kotlin in 2 Days

More Decks by WeRockStar

Other Decks in Programming

Featured

Transcript