AIDL : IPC, The Android way

The Android Interface Definition Language (AIDL) is similar to other IDLs: it lets you define the programming interface that both the client and service agree upon in order to communicate with each other using interprocess communication (IPC).

Aidl consists of 3 parts:

AIDL file
Client application
Server application

Creating AIDL file

Enable build feature in your build.gradle.
```
 buildFeatures {
     aidl = true
 }
```
Create a new AIDL file using File -> New -> AIDL -> AIDL File
Let's name it ICalculator.aidl

Declare aidl methods:

 interface IExampleAidlInterface {
     int add(int a, int b);
 }

Create an AIDL server

An AIDL server is an app that does the actual work and sends back the result to requesting clients. One service can connect with multiple clients via Binders.

Steps:

Create a service, e.g. CalculatorService extends Service
Create an Implementation of ICalculator.Stub, lets name it CalculatorImpl

Implement methods:

 object CalculatorImpl : ICalculator.Stub() {
     override fun add(a: Int, b: Int): Int {
         return a + b
     }
 }

Expose your stub implementation with a service binder:

 class CalculatorService : Service() {
     override fun onBind(intent: Intent): IBinder {
         return CalculatorImpl
     }
 }

Now your service is ready to be consumed by your clients, now let's create a client application.

Create an AIDL client

An AIDL client is an app that binds to an AIDL service, calls API, and shows a response inside its views.

Steps:

Create a service connection:

 private var aidlService: ICalculator? = null
 private val serviceConnection = object : ServiceConnection {
     override fun onServiceConnected(name: ComponentName?, service: IBinder?) {
         aidlService = ICalculator.Stub.asInterface(service)
         Toast.makeText(applicationContext, "Service Connected", Toast.LENGTH_LONG).show()
     }

     override fun onServiceDisconnected(name: ComponentName?) {
         aidlService = null
         Toast.makeText(applicationContext, "Service Disconnected", Toast.LENGTH_LONG).show()
     }
 }

Connect to AIDL service via Binders.

 val serviceIntent = Intent()
 serviceIntent.component = ComponentName(BuildConfig.AIDL_PACKAGE, BuildConfig.AIDL_SERVICE)
 bindService(serviceIntent, serviceConnection, BIND_AUTO_CREATE)

Call methods of AIDL after successful connection:

 aidlService?.add(2, 2)?.let {
     Toast.makeText(
         applicationContext,
         String.format(Locale.getDefault(), "Sum is: %d", it),
         Toast.LENGTH_LONG
     ).show()
 }

Limitations

There is one BIG gotcha with AIDL services, which is when the system is in doze mode, your service app might not start to respond to requests.

Here is an example application using AIDL in real life 😎

https://github.com/tejpratap46/AIDL-Example

AIDL : IPC, The Android way

Comments

More from this blog

How to create a lifecycle aware custom class in Android.

How to use Bitwise while setting properties

Limitation of PowerMockito.whenNew()

Android: How to create Custom Calendar with RecyclerView

Creating AIDL file

Create an AIDL server

Create an AIDL client

Limitations

Command Palette

Comments

More from this blog

Creating AIDL file

Create an AIDL server

Create an AIDL client

Limitations