Build an Android App with Google Home APIs: Devices, Structures, and Commissioning

Setting Up Your Development Environment

• 💡 Ensure you have the latest Android Studio installed, an Android phone with Google Play Services and the Google Home app, and a compatible Google Home Hub for Matter devices.
• 🛠️ For virtual devices, refer to the developer center for setup instructions and linking your device to the Google Home app.
• 🚀 Clone the sample app source code from GitHub and locate the to-do blocks in the comments where you will add code.
• 🔌 Connect your physical Android phone to Android Studio, enabling USB debugging in developer options if needed.

Authentication and Permissions

• 🔑 The Home APIs use OAuth 2.0 for authentication, allowing users to grant permissions without exposing login credentials.
• ☁️ Set up your OAuth consent screen in the Google Cloud console, choosing between internal or external use cases and adding test users.
• 📱 Register your sample app for OAuth 2.0, ensuring you indicate the application type as an Android app.
• ⚙️ Initialize the SDK by defining supported device types and traits in the home_app.kt file and configuring the home_client object.
• ✅ Implement the checkPermissions and requestPermissions functions in the permissions_manager.kt file to handle user permissions.

Device and Structure APIs

• 🏠 The Home API data model consists of structures (homes), rooms, devices, device types, traits, and automations.
• 📊 Structures contain rooms, which in turn contain devices. Devices are composed of device types and traits.
• 🔄 Use Kotlin Flows to stream data model objects; subscribe to the structures function to get a flow of structures and then call list to retrieve all owned structures.
• 📱 In the home_app_view_model.kt file, implement code to subscribe to structure changes and store view models, selecting the first structure if none is selected.
• 🗂️ Render the structure list as a drop-down menu in the devices_view.kt file by subscribing to the structure view model state flow.
• 💡 To retrieve device states, subscribe to the device type flow. Each device has supported types and traits that define its capabilities.
• 🔌 Implement to-do blocks in the device_view_model.kt to determine primary types and get supported traits, then render an on-off trait in the device_view.kt file.
• 🕹️ Issue commands to devices using convenience functions on trait objects, such as trait.on() or trait.moveToLevel().

Commissioning Matter Devices

• 🔌 The commissioning API allows you to add Matter devices to the Google Home ecosystem.
• ⚠️ This section requires a Matter device and a compatible Google Hub that supports Matter.
• 🚀 Set up two variables for the commissioning API: an ActivityResultLauncher to send the commissioning intent and manage callbacks, and commissioningResult to store the outcome.
• 📲 Build and launch the commissioning intent, ideally within a dedicated function tied to a UI element like an "Add Device" button.
• 🤳 Running the app will display an "Add Device" button that initiates the commissioning flow, including QR code scanning, user agreement, device discovery, and naming.
• ✅ Upon completion, control is returned to the app with the commissioning result passed back to the callback function.