When Google presented Android Wear, we started to experiment with the Developer preview, and while at this time we’re limited to using only notifications (since currently, there is no real Android Wear SDK), the results are surprisingly good. This example will show you how to create a horizontally swipeable, card-like notification for Android Wear.

We’re working on an app that aggregates the most recent interactions associated with the caller and shows them as cards when the phone is ringing. While the ringer screen gives a great way to get an idea of why they’re calling, it is obviously limited: if you don’t pick up in 5-6 seconds, they’ll hang up for sure. This is why we’ve been actively working on the concept of a second-screen experience since day one, mostly thinking about tablets as the secondary source of information. However, a smartwatch makes much more sense: you can see the caller-related information not only on your phone before a call, but while you’re talking, and you don’t have to carry an extra tablet around.

The Android Wear Developer preview is not available for anyone, you’ll have to register to get an invite (you can do so here). I won’t go into details on how to get started with the SDK, since Google’s official site covers the subject perfectly.

Disclaimer: Google points out that the Wear Developer Preview is intended for development and testing purposes only, not for production apps. This means it will no longer be supported after the official SDK is released, so apps using it will most likely break.

As of now, the only way to interact with Wear devices is via notifications. All notifications are mirrored to the emulator (of course, they appear in a transformed way), but it is possible to create enhanced Notifications with the WearableNotifications.Builder class. This is basically a wrapper around the NotificationCompat.Builder, allowing the developer to extend the notifications with Wear-exclusive capabilities, like receiving voice input, hiding the app icon, making them stackable, adding multiple actions with different icons and spanning a single notification through multiple pages.

This example will demonstrate the latter. Every page represents an event related to the caller (an email, a message, a meeting, etc.), encapsulated in the ultra-primitive Card class. The first step is creating a parent notification, nothing new, just some standard calls on the NotificationCompat.Builder: setting a small and a large image (the latter represents the caller), a title and a description (and a PendingIntent, which is deliberately left out in this example).

final NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(WearableActivity.this)
    .setLargeIcon(BitmapFactory.decodeResource(getResources(), R.drawable.caller_picture))
    .setContentTitle("Incoming call")
    .setContentText("Name of the caller");

The content cards are built while iterating through the list of Card instances. A NotificationCompat.BigTextStyle is created for each Card, with the title and description set properly, each of these added to a list of Notifications.

for (Card card : cards) {
    final NotificationCompat.BigTextStyle bigTextStyle = new NotificationCompat.BigTextStyle();

    notifications.add(new NotificationCompat.Builder(WearableActivity.this)

Next, simply wrap the parent Notification into a WearableNotification and set the generated pages.

Notification twoPageNotification = new WearableNotifications.Builder(notificationBuilder)

The final step is to show the Notification, this is done in the standard way.

((NotificationManager) WearableActivity.this.getSystemService(Context.NOTIFICATION_SERVICE)).notify(NOTIFICATION_ID, twoPageNotification);

The sample (wrapped in an Activity) is available as a Gist. You can find more info and tutorials on the Android Wear Developer Preview here, and don’t forget to check out the design guidelines and the UI overview.