louis993546

Resources for Mental Modles of Jetpack Compose

Here's list of things you might be interested

The slides that brought you here (probably)

Directly Jetpack-Compose-related

• The original Google I/O talk that announces Jetpack Compose
• Official page for Jetpack Compose
• A simplified version of how Jetpack Compose works on a technical level

louis993546

Jetpack Compose and how did we end up here?

Index

• The birth of modern smartphones
• React is taking over the world
• Reacting to React
• How does Jetpack Compose fit into the picture

The birth of modern smartphone

louis993546

@Composable
internal fun Text(/* params */) {
  /* a lot of magic */
  val children = @Composable {
    Draw { canvas, _ ->
      internalSelection.value?.let { renderParagraph.paintSelection(canvas, it) }
      renderParagraph.paint(canvas, Offset(0.0f, 0.0f))
    }
  }
  /* a lot more magic */

louis993546

import androidx.compose.*
import androidx.ui.core.*

@Composable
fun Greeting(name: String) {
    Text ("Hello $name!")
}

louis993546

Diving into Jetpack Compose and see what's inside

Draft of what I will present

• What Google said Jetpack Compose is
• A really really quick recap of how Android draw stuff on screen right now
• A quick look at the example code (i.e. how to use it)
• Dig into how it actually works
  • What is it made of
• Runtime

louis993546

class PresenterWithDI(
  private val networking: NetworkWrapper,
  private val crashReporting: CrashReporting
) {
  fun onSaveClicked() {
    val (response, error) = networking.callTheApi()
    if (error != null) 
      crashReporting.log("Oh no")
    else
      Log.d("DI", "Yay")

louis993546

val currentLocation: Observable<LatLong> = TODO("the platform API keeps sending signal to this object")

currentLocation.subscribeBy(
  onNext -> { latLong -> moveThePin(latLong) }, 
  onError -> { throwable -> TODO("tell user that current location is not retrievable or something") }, 
  onComplete -> { TODO("this is the end of the transmission, turn it off or something") })

fun moveThePin(latLong: LatLong) { TODO("move the Pin") }

louis993546

interface ViewHolderFactory {
  fun createViewHolder(parent: ViewGroup, onClick: () -> Unit): ViewHolder
}

class ViewHolderFactoryImpl1 : ViewHolderFactory {
  override fun createViewHolder(parent: ViewGroup, onClick: () -> Unit): ViewHolder = TODO("")
}

class ViewHolderFactoryImpl2 : ViewHolderFactory {
  override fun createViewHolder(parent: ViewGroup, onClick: () -> Unit): ViewHolder = TODO("")

louis993546

class SomeAdapter(
  val factory1: ViewHolderFactory1,
  val factory2: ViewHOlderFactory2
): RecyclerView.Adapter<RecyclerView.ViewHolder>() {
  override fun getItemViewType(position: Int) = if (position == 0) 1 else 2
  
  override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) = when (viewType) {
      1    -> factory1.createViewHolder(parent)
      2    -> factory2.createViewHolder(parent)
      else -> error("This should not be possible")

louis993546

class SomethingActivity extends AppCompatActivity {
  @Override
  void onCreate() {
    super.onCreate();
    setContentView(R.layout.activity_something);
  }
  
  @Override
  void onResume() {
    retrofitService.someApiEndpoint().enqueue(this);