by Jamie Sanson27 May 2025
Target AudienceLeeds Mobile
45 Slides1784 Words
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Exploring Android 16

App Functions

I/O Extended @ Leeds Mobile - May 2025

Jamie Sanson

Staff Software Engineer @ M&S

App Functions

Agenda

  • App Functions - what are they?
  • Building an App Function
  • Calling an App Function
  • What are they for?
  • Predictions 🔮

More specific Intent

An app function is a piece of functionality that apps expose to the system for cross-app orchestration.

AndroidX App Functions

Browsing AndroidX

https://cs.android.com

App Function packages

  • appfunctions: backwards compatibility?
  • appfunctions-compiler: annotation processing is involved
  • appfunctions-service: seems to be a separate runtime library

The [appfunctions.metadata] package defines a set of classes to represent metadata for AppFunctions. This metadata is designed to be similar in spirit to the OpenAPI specification, which is used to describe REST APIs. 1

  1. https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:appfunctions/appfunctions/src/main/java/androidx/appfunctions/metadata/README.md ↩︎

App Function metadata

  • No HTTP-related things like response codes
  • Metadata is stored in AppSearch
  • Metadata originates in your APK
  • Common, versioned “schemas”

What the code tells us

  • Apps include “functions”
  • Functions have request/response modelling
  • Requests & responses form function metadata
  • Codegen will make writing functions easier

Using App Functions

Downloading AndroidX Snapshots

https://androidx.dev

// in settings.gradle.kts
dependencyResolutionManagement {
    repositories {
        google()
        mavenCentral()
+       maven {
+           url = uri("https://androidx.dev/snapshots/builds/<build-number>/artifacts/repository")
+       }
    }
}

// in settings.gradle.kts
dependencyResolutionManagement {
    repositories {
        google()
        mavenCentral()
        maven {
            url = uri("https://androidx.dev/snapshots/builds/<build-number>/artifacts/repository")
+           content {
+               includeGroup("androidx.appfunctions")
+           }
        }
    }
}

Writing an App Function

AndroidX AppFunctions

  • KSP plugin
  • @AppFunction
  • A bound Service
  • Various other things (schema, serialization annotation)

💻

Calling an App Function

AppFunctionManager

  • Search for functions
  • Invoke functions
  • Enable and disable functions

💻

Why can’t I call App Functions?

💻

What are they for?

Function calling (AKA MCP)

App Functions and function calling

  • Function definitions from AppSearch
  • Serviced using EXECUTE_APP_FUNCTIONS
  • Your app is a set of tools

Similar things to iOS App Intents?

Predictions 🔮

App Functions are probably for LLMs

We won’t see them in production for a while

Android could be becoming ✨ agentic ✨

Conclusions

Conclusions

  • App Function are better Intents
  • You can build them
  • You can’t call them
  • Their use-case is probably AI, but could be used in isolation

⍰ Questions ⍰

Thanks!

@jamiesanson