Android Wear Realm Database Sync

A_DATABASEWEAR.md

This short code will show how to sync database file using Realm, but can be used for any file that you need to send to Wear (using Data API). It just takes any file, change it to Asset object and send it over to Wear device. Also it can be used Mobile->Wear, and Wear->Mobile.

When you need to sync database just call FileSender.syncRealm(context);, that is it!

DISCLAIMER "Proper" way would be to synchronize each transaction to DB, but it in most cases Wear is used very rarely comparing to mobile, so it would most likely cause a battery drain. My idea was to synchronize it only whene it is needed (so for example when app closes). If you want to make sure that you are using latest DB, just send trigger data using MessageAPI from Wear to Phone with ask of syncing over its database, or keep some timestapm of last edit and check it.

FileSender.java

public class FileSender extends AsyncTask<Void, Void, Void> {
    private Asset asset;
    private Context context;
    private GoogleApiClient mGoogleAppiClient;
    private static final String TAG = "AssetsSender";

    public FileSender(Asset asset, Context context) {
        this.asset = asset;
        this.context = context;
    }

    @Override
    protected Void doInBackground(Void... params) {
        sendData(asset);
        return null;
    }

    @Override
    protected void onPreExecute() {
        mGoogleAppiClient = new GoogleApiClient.Builder(context)
                .addApi(Wearable.API)
                .build();
        mGoogleAppiClient.connect();
    }

    private void sendData(Asset asset) {
        if(asset == null){
            return;
        }
        PutDataMapRequest dataMap = PutDataMapRequest.create("/ourAppDatabase");
        byte[] arr = asset.getData();
        dataMap.getDataMap().putByteArray("realmDatabase", arr);//for some reason .putAsset wasn't working for me in some cases
        PutDataRequest request = dataMap.asPutDataRequest();
        PendingResult<DataApi.DataItemResult> pendingResult = Wearable.DataApi.putDataItem(mGoogleAppiClient, request);
        pendingResult.setResultCallback(new ResultCallback<DataApi.DataItemResult>() {
            @Override
            public void onResult(DataApi.DataItemResult dataItemResult) {
                Log.d(TAG, "onResult result:" + dataItemResult.getStatus());
            }
        });
    }

    public static void syncRealm(Context context){
        File writableFolder = context.getFilesDir();
        File realmFile = new File(writableFolder, Realm.DEFAULT_REALM_NAME);
        Asset realAsset = Tools.assetFromFile(realmFile);
        new FileSender(realAsset, context).execute();
    }
}

ListenerService.java

public class ListenerService extends WearableListenerService {
    //Remember to decler it as well in Manifest.xml
    private static final String TAG = ListenerService.class.getSimpleName();
    
    @Override
    public void onDataChanged(DataEventBuffer dataEvents) {
        Log.d(TAG, "onDataChanged");
        final List<DataEvent> events = FreezableUtils.freezeIterable(dataEvents);
        dataEvents.close();
        for (DataEvent event : events) {
            Uri uri = event.getDataItem().getUri();
            String path = uri.getPath();
            if ("/ourAppDatabase".equals(path)) {
                DataMapItem item = DataMapItem.fromDataItem(event.getDataItem());
                byte[] realmAsset = item.getDataMap().getByteArray("realmDatabase");
                if(realmAsset != null){
                    toFile(realmAsset);
                    //I recommend here calling a Broadcast - getBaseContext().sendBroadcast(new Intent(yourbroadcast here));
                }
            }
        }
    }

    private void toFile(byte [] byteArray){
        File writableFolder = ListenerService.this.getFilesDir();
        File realmFile = new File(writableFolder, Realm.DEFAULT_REALM_NAME);
        if (realmFile.exists()) {
            realmFile.delete();
        }
        try {
            FileOutputStream fos=new FileOutputStream(realmFile.getPath());
            fos.write(byteArray);
            fos.close();
        }
        catch (java.io.IOException e) {
            Log.d(TAG, "toFile exception: " + e.getLocalizedMessage());
        }
    }
}

Hey ... I am getting error when I tried to query the new contents in the realm file. It returns null entry and app crashes. When I again reopen the app, realm return entries for same query. Where is the problem.?