Android Development Workshop

This is a workshop that i gave to at the University of Johannesburg in 2018.
In 2019 I did a similar workshop, but the project we built was an API with Ktor.

https://github.com/pjwelcome/Ktor-StarterProject
https://github.com/pjwelcome/AndroidWorkshop

Transcript

1. Android Development
   Workshop
   Peter-John Welcome
   @pjapplez
   Mobile Engineering Lead
   

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2. Day 1
   

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3. What we will do Today:
   Intro:
   1. Create our first Android app and run it.
   2. Git Crash Course
   3. Learn Kotlin for Android
   4. Crash Course on Android Layouts. (Constraint Layouts)
   5. RecyclerViews (View Holder Pattern)
   

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4. Let’s open Android Studio
   

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5. Android Dependencies
   dependencies {
   implementation fileTree(dir: 'libs', include: ['*.jar'])
   implementation"org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
   implementation 'com.android.support:appcompat-v7:27.1.1'
   implementation 'com.android.support.constraint:constraint-layout:1.1.2'
   implementation 'com.android.support:recyclerview-v7:27.1.1'
   }
   

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6. What is git?
   

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7. What is git?
   ● Git is an example of a DVCS (hence Distributed Version Control System)
   

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8. Kotlin
   

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9. Google announced Kotlin will be an official language for Android
   

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10. Why Kotlin over Java?
    ● Java is very verbose.
    ● Java Code is error prone with all its anonymous inner classes.
    ● Java lacks modern language features.
    ● Nullability issues.
    

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11. Language Features
    

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12. var/val
    var name : String = "Peter"
    name = "John"
    val surname = "Welcome"
    surname = "Johnson" // val can’t be reassigned
    

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13. Number one reason Android Apps
    Crash?
    

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14. Null Pointer Exception
    

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15. Nullability
    var name : String = "Peter"
    name = null // null can’t be a value on a non-null String
    var surname : String? = "Peter"
    surname = null
    val otherName = surname ?: "" // Elvis operator ( ?? in other languages)
    

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16. Classes
    

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17. Classes
    class User {
    private val name: String
    private val surname : String
    constructor(name : String , surname: String) {
    this .name = name
    this.surname = surname
    }
    }
    var user = User( surname = "Welcome", name = "Peter") // named arguments
    

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18. Data class
    @Parcelize
    data class Human (private var name: String, val age: Int) : Parcelable
    //copy, equal, hashcode, toString
    var human = Human("Peter",27)
    

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19. Sealed Classes
    sealed class Result{
    data class Success (val value : T) : Result()
    data class Error(val error : MyError) : Result()
    }
    

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20. Sealed Classes
    fun resultsFromService(result : Result) : String {
    when (result) {
    is Result.Success -> "${result.value} World"
    is Result.Error -> return result.error.toString()
    }
    return ""
    }
    resultsFromService(Result.Success("Hello"))
    

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21. Functions
    

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22. First class citizens
    

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23. High order functions
    

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24. Functions
    fun hello(){
    print("Hello")
    }
    val functionAsVariable = hello()
    val greetingPeter = fun (func : (name :String) -> String ) : String = func("Peter")
    greetingPeter {
    "Hello $it"
    }
    

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25. Extension functions
    

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26. Extension functions
    infix fun Int.add (value : Int) = this + value
    val result = 1.add(1)
    val result = 1 add 1
    //Extension function
    fun Observable.applySchedulers() : Observable =
    this.subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread())
    //Usage
    disposable.add(this.viewModel.createPlant(Plant(name = "Best Plant
    Ever")).applySchedulers().subscribe ())
    

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27. Function Literals with Receiver
    

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28. Function Literals with Receiver
    inline fun SharedPreferences.edit(action: SharedPreferences.Editor.() -> Unit) {
    val editor = edit()
    editor.action()
    editor.apply()
    }
    getSharedPreferences("cache", Context.MODE_PRIVATE).edit {
    putString("username", "Peter")
    }
    

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29. Async Programming
    

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30. AsyncTasks
    class doAsyncTask(textView: TextView) : AsyncTask() {
    val innerTextView: TextView? = textView
    override fun doInBackground(vararg params: Unit?): String? {
    try {
    ...
    return data
    } catch (e: Exception) {
    return null
    }
    }
    override fun onPostExecute(result: String?) {
    super.onPostExecute(result)
    innerTextView?.text = JSONObject(result).toString()
    }
    }
    

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31. AsyncTasks
    

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32. RxJava
    disposable.add(viewModel.fetchDashboardPlants()
    .applySchedulers()
    .subscribe({
    //onNext:
    ...
    }, { error ->
    //onError
    })
    )
    fun Observable.applySchedulers() : Observable =
    this.subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread())
    

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33. Coroutines
    internal val background = newFixedThreadPoolContext(2, "background")
    launch (background) {
    val result = resultsFromService(Result.Success("Hello"))
    launch(UI) {
    this.textView.text = result
    }
    }
    // The async await way
    val someLongRunningTask = async(CommonPool) {
    return@async ""
    }.await()
    

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34. Let’s build our app.
    

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35. Life Cycles and Resources
    

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36. Layouts (Constraint Layout)
    

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37. RecyclerView
    

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38. RecyclerView
    
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >
    android:id="@+id/rv_item_repo"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />
    
    

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39. RecyclerView
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    android:id="@+id/tv_animal_type"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="8dp"
    android:layout_marginTop="48dp"
    android:layout_marginEnd="16dp"
    android:text="animal name"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />
    
    

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40. RecyclerView
    class AnimalAdapter(val items: ArrayList) : RecyclerView.Adapter() {
    // Gets the number of animals in the list
    override fun getItemCount(): Int {
    return items.size
    }
    // Inflates the item views
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
    return ViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.animal_list_item, parent, false))
    }
    // Binds each animal in the ArrayList to a view
    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
    holder.tvAnimalType.text = items.get(position)
    }
    }
    class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
    // Holds the TextView that will add each animal to
    val tvAnimalType = view.tv_animal_type
    }
    

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41. Slides
    https://tinyurl.com/ycb3cn7f
    Workshop Feedback
    https://bit.ly/2uFagmK
    

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