Exercise

Exercise is an kotlin symbol processor for Android projects. Exercise makes it possible to pass intent extras easily and correctly.

Getting started

First, add it to gradle.

Kotlin multiplatform

repositories {
  mavenCentral()
}

kotlin {
  android()

  val androidMain by getting {
    dependencies {
      implementation("com.juul.exercise:annotations:$version")
      implementation("com.juul.exercise:runtime:$version")
    }
  }
}

dependencies {
  add("kspAndroid", "com.juul.exercise:compile:$version")
}

Android project

repositories {
  mavenCentral()
}

dependencies {
  implementation("com.juul.exercise:annotations:$version")
  implementation("com.juul.exercise:runtime:$version")
  ksp("com.juul.exercise:compile:$version")
}

Then, create your activity.

@Exercise(Extra("someNumber", Int::class))
class YourActivity : AppCompatActivity() {
  // ...

  fun useExtras(): Int = 2 * extras.someNumber
}

Finally, navigate to it.

class FromActivity : AppCompatActivity() {
  // ...

  fun navigate() {
    startActivity(YourActivityIntent(this, someNumber = 25))
  }
}

Nullables and Optionals

To make an Extra nullable, you mark it as optional. Declaration and use:

@Exercise(Extra("anyString", String::class, optional = true))
class OptionalsActivity : AppCompatActivity() {
  // ...

  fun useExtras() {
    println(extras.anyString) // nullable
    println(extras.anyString(default = "someDefault")) // non-null with function call
  }
}

Creating the intent:

// Works with a nullable argument
fun getString(): String? = TODO()
OptionalsActivityIntent(context, anyString = getString())

// Argument has a default value of null, so it can be left off.
OptionalsActivityIntent(context)
// The above is same as the below
OptionalsActivityIntent(context, anyString = null)

Parcelers

Exercise works with KotlinX Parceler The following example assumes you are consuming some external code:

data class ThirdPartyType(val value: String)

First, write a Parceler just like you would for a @Parcelize class (or reuse an existing one).

object ThirdPartyTypeParceler : Parceler<ThirdPartyType> {
  override fun create(parcel: Parcel) = ThirdPartyType(checkNotNull(parcel.readString()))

  override fun ThirdPartyType.write(parcel: Parcel, flags: Int) {
    parcel.writeString(this.value)
  }
}

Declaration and use:

@Exercise(Extra("myThirdPartyType", ThirdPartyType::class, parceler = ThirdPartyTypeParceler::class))
class ThirdPartyTypeActivity : AppCompatActivity() {
  // ...

  fun useExtras() {
    println(extras.myThirdPartyType)
  }
}

Creating the intent:

ThirdPartyTypeActivityIntent(context, myThirdPartyType = ThirdPartyType("Some string"))

Services

Exercise supports intents for a Service much like an Activity.

@Exercise(Extra("someNumber", Int::class))
class YourService : JobIntentService() {
    override fun onHandleWork(intent: Intent) {
        println("Some Number: ${extras(intent).someNumber}")
    }
}

Creating the intent:

val intent = YourServiceIntent(context, someNumber = 5)

Launching a JobIntentService:

JobIntentService.enqueueWork(context, YourService::class, jobId, intent)

Launching other Services:

context.startService(intent)

Make IDE aware of generated code

To have code generated by KSP (e.g. Exercise) recognized in your IDE, add the following to your root build.gradle.kts:

subprojects {
    project.plugins.whenPluginAdded {
        if (this is org.jetbrains.kotlin.gradle.plugin.KotlinBasePlugin) {
            project.extensions.configure<org.jetbrains.kotlin.gradle.dsl.KotlinProjectExtension> {
                sourceSets.forEach { sourceSet ->
                    sourceSet.kotlin.srcDir("build/generated/ksp/${sourceSet.name}/kotlin")
                }
            }
        }
    }
}

See Make IDE aware of generated code for more details.

License

Copyright 2020 JUUL Labs, Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.