A better way to launch activities. Companion code to https://medium.com/@ZakTaccardi/a-better-way-to-launch-activities-8a1045181b16

BetterWayToLaunchActivities.kt

@file:Suppress("unused", "FunctionName", "IllegalIdentifier")

import android.annotation.SuppressLint
import android.app.Activity
import android.content.Context
import android.content.Intent
import android.os.Bundle

/**
 * The best way to launch yourself an activity. Your implementation should enable the following api:
 *
 * ```kotlin
 * YourActivityArgs(param1, param2)
+                .launch(activityContext);
 * ```
 *
 * Your deserialization (from an intent) could look like:
 *
 * ```kotlin
 * YourActivityArgs.of(intent)
 * ```
 */
interface ActivityArgs {

  /**
   * @return returns an intent that can be used to launch this activity.
   */
  fun intent(activity: Context): Intent

  /**
   * Launches the activity given your activity context.
   *
   * The default implementation uses the intent generated from [intent]
   */
  fun launch(activity: Context) = activity.startActivity(intent(activity))
}

@SuppressLint("Registered")
class MediumProfileActivity : Activity() {

  private val args by lazy {
    MediumProfileActivityArgs.deserializeFrom(intent)
  }

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    // easily reference` your activity's arguments!
    args.name
    args.shortBio
    args.profilePhotoUrl
  }
}

/**
 * Arguments to launch [MediumProfileActivity]
 */
data class MediumProfileActivityArgs(
    val name: String,
    val shortBio: String,
    val profilePhotoUrl: String
) : ActivityArgs {

  override fun intent(activity: Context): Intent = Intent(
      activity, MediumProfileActivity::class.java
  ).apply {
    putExtra(NAME_KEY, name)
    putExtra(SHORT_BIO_KEY, shortBio)
    putExtra(PROFILE_PHOTO_URL_KEY, profilePhotoUrl)
  }

  companion object {
    fun deserializeFrom(intent: Intent): MediumProfileActivityArgs {
      return MediumProfileActivityArgs(
          name = intent.getStringExtra(NAME_KEY),
          shortBio = intent.getStringExtra(SHORT_BIO_KEY),
          profilePhotoUrl = intent.getStringExtra(PROFILE_PHOTO_URL_KEY)
      )
    }
  }
}

private const val NAME_KEY = "name_key"
private const val SHORT_BIO_KEY = "short_bio_key"
private const val PROFILE_PHOTO_URL_KEY = "profile_photo_url_key"

@SuppressLint("Registered")
class SomeOtherActivity : Activity() {

  fun goToMediumProfile() {
    val currentActivity = this
    MediumProfileActivityArgs(
        "Zak Taccardi",
        "Eat. Sleep. Android.",
        "www.profile.com/ZakTaccardi.png"
    )
        .launch(currentActivity)
  }
}

@Test
fun `test args serialization and de-serialization`() {
  val expectedArgs = MediumProfileActivityArgs(
      "Zak Taccardi",
      "Eat. Sleep. Android.",
      "www.profile.com/ZakTaccardi.png"
  )

  // serialize args to intent
  val serializedIntent = expectedArgs.intent(context)
  // deserialize intent into args instance
  val actualArgs = MediumProfileActivityArgs.deserializeFrom(serializedIntent)
  // verify de-serialized args are equal to original args
  Assertions.assertThat(actualArgs)
      .isEqualTo(expectedArgs)
}

// the below serves to avoid red compilation errors above
annotation class Test

class Assertions {
  companion object {
    fun assertThat(actualArgs: MediumProfileActivityArgs) = AssertionHelper

    object AssertionHelper {
      fun isEqualTo(expected: MediumProfileActivityArgs) {}
    }
  }
}

@SuppressLint("StaticFieldLeak")
val context: Context = null!!

Well written ! 👍

In case anyone looking for startActivityForResult :

fun launchActivityForResult(activity: Activity,requestCode : Int) = activity.startActivityForResult(intent(activity),requestCode)