Building an Android Wear app 

Anatomy of an Android Wear app 4 Wearable app 4 Mobile app, with wearable app packaged inside 4 Communicate via notifications and/or Google Play Services APIs 

Never Gonna GIF You Up 

Loading a random GIF on the watch 1. UI library for displaying GIFs 2. Request random GIF from Giphy API 3. Make API request, update view 

Loading a random GIF on the watch 1. UI library for displaying GIFs 2. Request random GIF from Giphy API 3. Make API request, update view Most wearables don't have internet...yet 

Wearable app 

Wearable app 1. UI library for displaying GIFs 2. Request GIF from mobile app 3. Listen for data change from phone 4. Update view 

Request GIF from mobile app Set nodes = Wearable.CapabilityApi .getCapability(googleApiClient, "gif_me", CapabilityApi.FILTER_REACHABLE) .await() .getCapability() .getNodes(); if (!nodes.isEmpty()) { for (Node node : nodes) { Wearable.MessageApi.sendMessage(googleApiClient, node.getId(), "gif/random", null).await(); } } 

Listen for data changes @Override public void onDataChanged(DataEventBuffer dataEvents) { for (DataEvent event : dataEvents) { if (event.getType() == DataEvent.TYPE_CHANGED) { DataItem item = event.getDataItem(); if (item.getUri().getPath().compareTo("/image") == 0) { Asset asset = DataMapItem.fromDataItem(item).getDataMap().get("random_gif"); // Do something with asset } } } } 

Mobile app 

Mobile app 1. WearableListenerService to listen for GIF requests 2. Request random GIF from Giphy API 3. Push file bytes to wearable via Data API 

Registering a WearableListenerService - AndroidManifest.xml 

Registering a WearableListenerService: res/values/wear.xml gif_me 

WearableListenerService public class GifRequestWearableListenerService extends WearableListenerService { @Override public void onMessageReceived(MessageEvent messageEvent) { if (messageEvent.getPath().equals("gif/random")) { bytes[] imageBytes = getRandomGif(); Asset asset = Asset.createFromBytes(imageBytes) pushAsset(asset); } } private void pushAsset(Asset asset) { PutDataMapRequest request = PutDataMapRequest.create("/image"); request.getDataMap().putAsset("random_gif", asset); Wearable.DataApi.putDataItem(googleApiClient, request.asPutDataRequest()); } } 

Achtung! 4 Enable developer options and debugging on the wearable 4 Packaged wearable apps aren't automatically deployed for debug builds 4 Deploy the right app to the right device 4 It's difficult to debug end-to-end. Focus on one end at a time. 

Weird stuff 4 Retrolambda doesn't currently work with Android Wear. It seems to break the packaging of the wearable app into the mobile app.