With Wear OS by Google, a watch can communicate with a network directly, without access to an Android or iOS phone.
This page has the following dependencies and prerequisites:
- The latest version of Google Play services
- A Wear OS device or Wear AVD
Separately, the Wearable Data Layer API, which is part of Google Play services, provides an optional communication channel for apps. Although a Wear app can communicate with a phone app using the Wearable Data Layer API, connecting to a network using this API is discouraged. This API is currently only available on Android phones and Wear OS watches that are paired with Android phones. For Wear OS watches paired with iOS phones, apps can query other cloud-based APIs if Internet connectivity is available.
The Data Layer API consists of a set of data objects that the system can send and synchronize, along with listeners that notify apps of certain events, as follows:
- Data Item
DataItemprovides data storage with automatic syncing between the handheld and wearable.
Assetobjects are for sending binary blobs of data, such as images. You attach assets to data items and the system automatically takes care of the transfer for you, conserving Bluetooth bandwidth by caching large assets to avoid re-transmission.
MessageClientcan send messages and is good for remote procedure calls (RPC), such as controlling a handheld's media player from the wearable or starting an intent on the wearable from the handheld. Messages are also great for one-way requests or for a request/response communication model. If the handheld and wearable are connected, the system queues the message for delivery and returns a successful result code. If the devices are not connected, an error is returned. A successful result code does not indicate that the message was delivered successfully as the devices may disconnect after receiving the result code.
You can use a
ChannelClientto transfer large entities, such as music and movie files, from a handheld to a wearable device. Using a
ChannelClientfor data transfer has the following benefits:
- Transfer large data files between two or more connected devices,
without the automatic synchronization provided when using
Assetobjects attached to
ChannelClientsaves disk space over
DataClient, which creates a copy of the assets on the local device before synchronizing with connected devices.
- Reliably send a file that is too large to send using a
- Transfer streamed data, such as music pulled from a network server or voice data from the microphone.
- Transfer large data files between two or more connected devices, without the automatic synchronization provided when using
- WearableListenerService (for services)
WearableListenerServicelets you listen for important data layer events in a service. The system manages the lifecycle of the
WearableListenerService, binding to the service when it needs to send data items or messages and unbinding the service when no work is needed.
- OnDataChangedListener (for foreground activities)
OnDataChangedListenerin an activity lets you listen for important data layer events when an activity is in the foreground. Using this instead of the
WearableListenerServicelets you listen for changes only when the user is actively using your app.
Warning: Because these APIs are designed for communication between handhelds and wearables, these are the only APIs you should use to set up communication between these devices. For instance, don't try to open low-level sockets to create a communication channel.
Your phone and Wear APK signatures and the signature schemes must to be identical for
the DataLayer API to be able to successfully communicate between devices. This includes
your usage of the v1 and/or v2 signature. Ensure the signature scheme is set correctly
build.gradle or when you use the Generate Signed APK wizard.
Wear OS supports multiple wearables connected to a handheld device. For example, when the user saves a note on a handheld, it automatically appears on all of the user's Wear devices. To help synchronize data between devices, Google’s servers host a cloud node in the network of devices. The system synchronizes data to directly connected devices, the cloud node, and to wearable devices connected to the cloud node via Wi-Fi.
- Network access and syncing
- This lesson shows you how to acquire a high-bandwidth network. The lesson also provides a starting point for cloud messaging and more.
- Access the wearable data layer
- This lesson shows you how to create a client to access the Data Layer APIs.
- Sync data items
- Data items are objects that are stored in a replicated data store that is automatically synced from handhelds to wearables.
- Transfer assets
- Assets are binary blobs of data that you typically use to transfer images or media.
- Send and receive messages
- Messages are designed for fire-and-forget messages that you can send back and forth between the wearable and handheld.
- Handle data layer events
- Be notified of changes and events to the data layer.
- Migrate Wear apps to GoogleApi
- Migrate away from the GoogleApiClient class.