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Building a
career in
Android
Development
@magdamiu
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ABOUT ME
● Squad Leader Developer @Orange
● Android Google Developers Expert
● Trainer & Speaker
● Co-organiser GDG Pitesti & WTM Romania
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Employment history
Web Developer
Aug 2010 - Oct 2010
Android Developer
Nov 2010 - Aug 2015
Android Technical Lead
Sept 2015 - Dec 2019
Squad Lead Developer
Jan 2019 - Present
GDE Android
Feb 2019 - Present
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OOP
Q: What’s the object-oriented
way to become wealthy?
A: Inheritance
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Cohesion
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Coupling
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Best case scenario
Cohesion Coupling
high
low
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● Don’t Repeat Yourself
● Applicable whenever we copy / paste a piece of code
D.R.Y.
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● Keep It Simple and Stupid
● Whenever we want to implement a method to do all things
K.I.S.S.
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● You Ain’t Gonna Need It
● Don’t write code which is not yet necessary
Y.A.G.N.I.
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● Single responsibility (SRP)
● Open-closed (OCP)
● Liskov substitution (LSP)
● Interface segregation (ISP)
● Dependency inversion (DIP)
S.O.L.I.D.
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Design Patterns
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Law of Demeter
A B
B is a friend
of A
C
C is a
friend of
B
*Note: A friend of a friend is a stranger
Messages from A
to B are OK
Messages from A
to C are
discouraged
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“Tell, Don't Ask” Principle
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Objects vs Data
Tell, don’t ask.
Don’t talk to
strangers.
Dealing with
Objects?
Dealing with
Data?
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Kotlin
A modern and pragmatic
language for the industry, not an
academic one.
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● General-purpose
● FP + OOP
● Open source (Apache 2.0)
● Developed by JetBrains
● Static typing
What is Kotlin?
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Kotlin is 100% interoperable with Java
*.kt
*.java
Kotlin
compiler
Java
compiler
*.class *.jar
App
Kotlin
runtime
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// Elvis operator
val name: String? = null
val lengthOfName = name?.length ?: -1
println(lengthOfName)
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// Elvis operator
val name: String? = null
val lengthOfName = name?.length ?: -1
println(lengthOfName) // => -1
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class Utility {
// infix functions = functions with a single parameter
infix fun String.onto(other: String) = Pair(this, other)
}
fun main(args: Array) {
val blueShoes = "blue".onto("shoes")
val yellowScarf = "yellow" onto "scarf"
println(blueShoes) // => (blue, shoes)
println(yellowScarf) // => (yellow, scarf)
}
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fun String.removeFirstLastChar(): String =
this.substring(1, this.length - 1)
Receiver type
Receiver object
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Data classes are a concise way to create classes that just hold data.
Data classes
Function Price
Getters and Setters 0 Lei
equals() & hashCode() 0 Lei
toString() 0 Lei
componentN() 0 Lei
copy() 0 Lei
TOTAL FREE!
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Coroutines are lightweight
threads
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co + routines
coroutines
Cooperation Functions
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Clean Code
“Clean code is readable. It tells a
story.”
Uncle Bob, Clean Code
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Code quality
“measure”
WTFs/min
Few WTFs Developer
Many WTFs Developer
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Use intention-revealing names
Types Names
Classes and Objects Customer, Account, WikiPage
Methods postPayment, deleteAccount, displayPage
Solution domain names AccountVisitor
Problem domain names churnPerMonth
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“UNCLEAN” CODE CLEAN CODE
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users.filter{ it.job == Job.Developer }
.map{ it.birthDate.dayOfMonth }
.filter{ it <= 10 }
.min()
WARNING: Use explicit argument names and avoid using too often “it”
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users.filter{ user -> user.job == Job.Developer }
.map{ developer -> developer.birthDate.dayOfMonth }
.filter { birthDay -> birthDay <= 10 }
.min()
WARNING: Use explicit argument names and avoid using too often “it”
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fun sumUpUserPoints(): Int {
var sumAllPoints = 0
for (user in users) {
sumAllPoints += user.points
sendEmail(user)
}
return sumAllPoints
}
No side effects
Side effect
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fun computeSqrt(number: Double): Double {
if(number >= 0) {
return Math.sqrt(number)
} else {
throw RuntimeException("No negative please")
}
}
Nothing is something...
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fun getMovie(id: Int): Movie {
val movie = movieRepository.findMovie(id)
return movie ?: throw RuntimeException("Movie not found")
}
Throw exceptions
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sealed class MovieSearchResult
data class MovieFound(val movie: Movie) : MovieSearchResult()
object MovieNotFound : MovieSearchResult()
object DatabaseOffline : MovieSearchResult()
fun getMovie(id: Int): MovieSearchResult {
val movie = movieRepository.findMovie(id)
return if (movie == null) {
MovieNotFound
} else {
MovieFound(movie)
}
}
Return result class
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inputStream.use {
outputStream.use {
// do something with the streams
outputStream.write(inputStream.read())
}
}
“try-with-resources” in Kotlin - initial solution
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arrayOf(inputStream, outputStream).use {
// do something with the streams
outputStream.write(inputStream.read())
}
“try-with-resources” in Kotlin - improved solution
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private inline fun Array.use(block: ()->Unit) {
// implementation
}
use implementation
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Kotlin is about developer’s happiness and
productivity.
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Android
Jetpack
A set of libraries, tools and
guides to help make app building
quick and easy.
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Android Jetpack
Follow best practices
Fewer crashes and less
memory leaks with
backwards-compatibility
baked in.
No boilerplate code
You can focus on what
makes your app great.
Reduce fragmentation
Reduce complexity with
libraries that work
consistently across
Android versions and
devices.
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Android Jetpack
UI
Jetpack Compose
Foundation
AndroidX, Android KTX
Architecture
LiveData, ViewModel,
Lifecycle, Room,
Navigation, Paging, Hilt
Behaviour
Slices, Security,
Permissions
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*Recommended app architecture
Activity / Fragment
Model
Room
Remote Data source
Retrofit
SQLite
REST
API
ViewModel
LiveData
Repository
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Architecture Components: Room for databases
Components
Entity, Dao, Database
“Relations”
@Embedded, @Relation,
@ForeignKey
Queries
@Insert, @Update, @Delete,
@Query, @RawQuery
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Tools for Android development
CI/CD Pipeline
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Learning Plan
“A goal without a plan is just a
wish.”
Antoine de Saint-Exupéry
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Achievable Learning Plan
@Work
Code review
&
Pull Request
@Home
SWOT
&
OKRs
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@Work
Code review & Pull Request
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Reviewer
Author
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Author
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Writing the code
● Make sure you understand your task
● Refactor the code if it’s unreadable
● Write tests and follow the team conventions
● Format your code before commit it
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The boy scout rule
Leave the campground cleaner
than you found it.
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Before the code review
● Add relevant commit comments
● Send pull requests often
● Have minimum 2 reviewers (one is senior)
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After the code review
● Be humble
● You are on the same side with your reviewer(s)
● Know when to unlearn the old habits
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Reviewer
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Use I… comments
● I think…
● I would…
● I believe…
● I suggest...
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Ask questions
● Have you consider using… ?
● What do you think about… ?
● Have you tried to… ?
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It’s about the code, not about the coder
● This code…
● This function…
● This line of code...
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Feedback equation*
Observation
of a behavior
Impact
of the behavior
Question or
Request
I observed this function
has 60 lines.
This makes it difficult for
me to understand the
logic.
I suggest extracting a
part of the code into
other functions and give
them relevant names.
*
Defined by Lara Hogan
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@Home
SWOT & OKRs
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The “process”
SWOT
Where I am now
Retro
How it was and
what’s next
OKRs
What I want to
achieve
Review
What I achieved
01 02
04 03
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Personal SWOT Analysis
ME
Weaknesses
Skills that should be
improved (technical or
work habits)
Threats
Impediments at work,
changes, weaknesses
lead to threats
Strengths
Advantages like: skills,
achievements,
certifications, education,
connections
Opportunities
Events, conferences, new
role/project, industry
growing
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● Goal setting in a collaborative way
● Objective => WHAT
● Key results => HOW
● “It’s not a key result unless it has a number”
OKRs
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● Superpower #1 => focus and commit to priorities
● Superpower #2 => align and connect for teamwork
● Superpower #3 => track for accountability
● Superpower #4 => stretch for amazing
OKRs superpowers
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● 0.7 to 1.0 = green (we delivered)
● 0.4 to 0.6 = yellow (we made progress, but fell short of completion)
● 0.0 to 0.3 = red (we failed to make real progress)
Scoring @Google
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OKR sample
Learn Kotlin for Android Development
6 months / weekly review
Quantity Goal Quality Goal Result
1 Kotlin Koan per week Learn specific features of the
language => 1 feature / week
Exercise often and on a set of
Koans proposed by JetBrains
Write one detailed article
about a specific topic per
month
Improve my writing skills and
learn by teaching to others
Learn new things, help the
community and get feedback
3 code samples runned per
week
Get a repo with samples that I
can re-check (use ktlint)
Gain real experience in
programming using Kotlin
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● Score your results
● Keep notes of your accomplishments
● Look for feedback because development is continuous
● Surround yourself with people who motivate and inspire you
● Find a mentor
Review
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● Did I accomplish all of my objectives?
○ YES => what contributed to my success?
○ NO => what obstacles did I encounter?
● If I were to rewrite a goal achieved in full, what would I change?
● What have I learned that might alter my approach to the next cycle’s
OKRs?
● Understand what is your WHY
● Repeat the process
Retrospective
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Official Documentation from Google
Blogs and Websites
Code Examples (Codelabs & GitHub)
Newsletters
Books & Online Courses
From where to learn more...
Videos & Youtube Channels
Podcasts
Twitter
Conferences & Meetups
Troubleshooting
https://magdamiu.com/2019/09/22/lets-talk-android/
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● Define with your colleagues a set of conventions
● Justify technology use
● Enforce good practices (XP)
● Question until you understand
● Criticize ideas, not people
● Testing, testing, testing
● Integrate early, integrate often
● Emphasize collective ownership of code
● Prioritize and actively evaluate trade-offs
● Listen to users
My summary
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CREDITS: This presentation template was created by Slidesgo,
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THANKS!
magdamiu.com
@magdamiu