intents

Intents

Transform companion objects into powerful typesafe intent specs, and create PendingIntents the clean and easy way.

Supported platforms: Android.

Setup

If you want to use this dependency without using one of the fun packs, you can use Splitties.intents, provided you have refreshVersions added to the project.

For reference, the maven coordinates of this module are com.louiscad.splitties:splitties-intents.

Table of contents

• Using companion objects as typesafe and key-safe intent specs
  • The problem about intents in Android
  • The solution
  • IntentSpec interfaces
  • IntentSpec implementations providers
  • Using an IntentSpec
  • IntentSpec example
• Creating PendingIntents the clean and easy way

Using companion objects as typesafe and key-safe intent specs

The problem about intents in Android

An Android component that can receive an Intent (like an Activity or a BroacastReceiver) can expect an action, or extras. In case of an action, the string must match exactly in order to work properly. In case of an extra, the type must also match. This makes it not typesafe at all. You need to write some documentation to explain which constants to use, with which types, and you need to be sure to read the doc afterwards, to ensure you do it right.

There should be a better way.

The solution

This split provides a few interfaces that your companion objects can implement using delegation so they become an intent specification, that you can use to build an Intent, start an Activity, start a Service or send a broadcast in a type safe way.

IntentSpec interfaces

The IntentSpec interface has two properties:

• klass which is the class of the component
• extrasSpec which is a BundleSpec (defined in the Bundle split).

The ActivityIntentSpec, BroadcastReceiverIntentSpec and ServiceIntentSpec interfaces all extend the IntentSpec interface, but add a bound to the type parameter of the class. You should use them when defining the intent spec of an Activity, BroadcastReceiver or Service.

IntentSpec implementations providers

A few methods provide implementation of the interfaces mentioned above:

• activitySpec
• activityWithoutExtrasSpec where ExtrasSpec is Nothing
• receiverSpec
• receiverWithoutExtrasSpec where ExtrasSpec is Nothing
• serviceSpec
• serviceWithoutExtrasSpec where ExtrasSpec is Nothing

They are designed to be used with by. Examples:

• companion object : ActivityIntentSpec<ProductDetailsActivity, ExtrasSpec> by activitySpec(ExtrasSpec)
• companion object : BroadcastReceiverIntentSpec<NotifDismissReceiver, ExtrasSpec> by receiverSpec(ExtrasSpec)

Using an IntentSpec

The intent method is an extension for IntentSpec. It takes a lambda where the receiver is the Intent. The first parameter is the companion object itself so you can access any constant or method defined in it easily. The second parameter of the lambda is optional, it is the extrasSpec.

The start method is an extension for Context and for Fragment that takes the target ActivityIntentSpec as its first parameter. It then calls the intent extension function mentioned above, and the optional expected lambda has the same parameters as for intent. Finally, it calls startActivity with the created Intent.

The sendBroadcast method is an extension for Context that takes the target BroadcastReceiverIntentSpec as its first parameter. It then calls the intent extension function mentioned above, and the optional expected lambda has the same parameters as for intent. Finally, it calls sendBroadcast with the created Intent.

IntentSpec example

Let's take the example shown in the Bundle README, adding an IntentSpec to it. Notice the new companion object and how we start the DemoActivity with the proper extras from the StartDemoActivity now.

class DemoActivity : AppCompatActivity() {

    companion object : ActivityIntentSpec<DemoActivity, ExtrasSpec> by activitySpec(ExtrasSpec) {
        const val someText = "Splitties is great!"
    }

    object ExtrasSpec : BundleSpec() {
        var showGreetingToast: Boolean by bundle() // Required extra
        var optionalExtra: String? by bundleOrNull() // Optional extra
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        withExtras(ExtrasSpec) { // Populates ExtrasSpec with actual extras
            if (showGreetingToast) toast(android.R.string.ok)
            optionalExtras?.let { longToast(it) }
        }
        restOfYourCode()
    }
}

class StartDemoActivity : AppCompatActivity() {

    private fun someFunction(isUserPolite: Boolean = false) {
        start(DemoActivity) { intentSpec, extrasSpec -> // Magic happens here!
            extrasSpec.showGreetingToast = isUserPolite
            extrasSpec.optionalExtra = intentSpec.someText
        }
    }
}

Creating PendingIntents the clean and easy way

It's fair to say that the PendingIntent Android API is not designed for Kotlin, and for a reason, it has been there since API level 1, the first Android version.

As a result, code using this API is not always the most readable part of a Kotlin codebase.

This split provides several extension functions for Intent that return a PendingIntent:

• toPendingActivity()
• toPendingService()
• toPendingForegroundService(), which also works before API 26
• toPendingBroadcast()

and an extension for Array<Intent>: toPendingActivities().

All these functions have two optional parameters that default to zero: reqCode and flags.

The toPendingActivity() and toPendingActivities() functions also have an options: Bundle? parameter that defaults to null (and is ignored below API 16).