Android Development

IC4J Agent library can be also used for development of native Android application written in Java or Kotlin. Use Android Studio to start a new Android application or add support for the Internet Computer to your existing application.

To add required IC4J libraries to your Android project open gradle.build file and add dependencies:

    implementation 'commons-codec:commons-codec:1.17.0'
    implementation 'org.ic4j:ic4j-candid:0.8.0'
    implementation('org.ic4j:ic4j-agent:0.8.0') {
        exclude group: 'org.apache.httpcomponents.client5', module: 'httpclient5'
    }
    implementation 'org.slf4j:slf4j-api:2.0.13'

Android application preferably uses OkHttp HTTP client so Apache HTTP 5 library can be excluded.

To be able to connect to the Internet Computer Canister set uses-permission in project AndroidManifest.xml descriptor.

<uses-permission android:name="android.permission.INTERNET"/>

Use IC4J with Kotlin

AndroidHelloWord sample application demonstrates use or QueryBuilder and UpdateBuilder in Kotlin Android project. Project properties ic.location and ic.canister are stored in strings.xml file.

MainActivity.kt has a simple code for QUERY and UPDATE invocation of the Canister code main.mo.

main.mo

actor {
    stable var name = "Me";

    public func greet(value : Text) : async Text {
        name := value;
        return "Hello, " # name # "!";
    };

    public shared query func peek() : async Text {
        return name;
    };
};

Using QueryBuilder in Kotlin.

MainActivity.kt

val url: String = getString(R.string.url)
val canister: String = getString(R.string.canister)

val identity: Identity = AnonymousIdentity()
val transport: ReplicaTransport =
                ReplicaOkHttpTransport.create(url)

val agent: Agent = AgentBuilder().identity(identity).transport(transport).build()
val buf = IDLArgs.create(ArrayList<IDLValue>()).toBytes()
val principal = Principal.fromString(canister);

val response = QueryBuilder.create(
                        agent,
                        principal,
                        "peek"
           ).arg(buf).call()

val output = response.get()
val outArgs = IDLArgs.fromBytes(output)
name = outArgs.args[0].getValue<String>()

Using UpdateBuilder in Kotlin.

MainActivity.kt

val url : String = getString(R.string.url)
val canister : String = getString(R.string.canister)

val identity : Identity = AnonymousIdentity()
val transport: ReplicaTransport =
                ReplicaOkHttpTransport.create(url)
val agent: Agent = AgentBuilder().identity(identity).transport(transport).build()

val arg : IDLValue = IDLValue.create(message)
var args : ArrayList<IDLValue> = ArrayList<IDLValue>()
args.add(arg)
val buf = IDLArgs.create(args).toBytes()

val response = UpdateBuilder.create(
                        agent,
                        Principal.fromString(canister),
                        "greet"
            ).arg(buf).callAndWait(Waiter.create(60, 5))

val output = response.get()
val outArgs = IDLArgs.fromBytes(output)
val outputMessage = outArgs.args[0].getValue<String>()