A key part of Android Wear 2.0 is letting watch apps work as standalone apps, so users can respond to messages, track their fitness, and use their favorite apps, even when their phone isn't around. Developer Preview 4 includes a number of new APIs that will help you build more powerful standalone apps.

Seamless authentication

To make authentication a seamless experience for both Android phone and iPhone users, we have created new APIs for OAuth and added support for one-click Google Sign-in. With the OAuth API for Android Wear, users can tap a button on the watch that opens an authentication screen on the phone. Your watch app can then authenticate with your server side APIs directly. With Google Sign-In, it's even easier. All the user needs to do is select which account they want to authenticate with and they are done.

In-app billing

In addition to paid apps, we have added in-app billing support, to give you another way to monetize your Android Wear app or watch face. Users can authorize purchases quickly and easily on the watch through a 4-digit Google Account PIN. Whether it's new levels in a game or new styles on a watch face, if you can build it, users can buy it.

Cross-device promotion

What if your watch app doesn't work standalone? Or what if it offers a better user experience when both the watch and phone apps are installed? We've been listening carefully to your feedback, and we've added two new APIs ( PlayStoreAvailability and RemoteIntent ) to help you navigate users to the Play Store on a paired device so they can more easily install your app. Developers can also open custom URLs on the phone from the watch via the new RemoteIntent API; no phone app or data layer is required.

// Check Play Store is available int playStoreAvailabilityOnPhone = PlayStoreAvailability.getPlayStoreAvailabilityOnPhone(getApplicationContext()); if (playStoreAvailabilityOnPhone == PlayStoreAvailability.PLAY_STORE_ON_PHONE_AVAILABLE) { // To launch a web URL, setData to Uri.parse("https://g.co/wearpreview") Intent intent = new Intent(Intent.ACTION_VIEW) .addCategory(Intent.CATEGORY_BROWSABLE) .setData(Uri.parse("market://details?id=com.google.android.wearable.app")); // mResultReceiver is optional; it can be null. RemoteIntent.startRemoteActivity(this, intent, mResultReceiver); }

Swipe-to-dismiss is back

Many of you have given us the feedback that the swipe-to-dismiss gesture from Android Wear 1.0 is an intuitive time-saver. We agree, and have reverted back to the previous behavior with this developer preview release. To support swipe-to-dismiss in this release, we've made the following platform and API changes:

Activities now automatically support swipe-to-dismiss. Swiping an activity from left to right will result in it being dismissed and the app will navigate down the back stack.

Swiping an activity from left to right will result in it being dismissed and the app will navigate down the back stack. New Fragment and View support. Developers can wrap the containing views of a Fragment or Views in general in the new SwipeDismissFrameLayout to implement custom actions such as going down the back stack when the user swipes rather than exiting the activity.

Developers can wrap the containing views of a Fragment or Views in general in the new to implement custom actions such as going down the back stack when the user swipes rather than exiting the activity. Hardware button now maps to "power" instead of "back" which means it can no longer be intercepted by apps.

Additional details are available under the behavior changes section of the Android Wear Preview site.

Compatibility with Android Wear 1.0 apps

Android Wear apps packaged using the legacy embedded app mechanism can now be delivered to Android Wear 2.0 watches. When a user installs a phone app that also contains an embedded Android Wear app, the user will be prompted to install the embedded app via a notification. If they choose not to install the embedded app at that moment, they can find it in the Play Store on Android Wear under a special section called "Apps you've used".

Despite support for the existing mechanism, there are significant benefits for apps that transition to the multi-APK delivery mechanism. Multi-APK allows the app to be searchable in the Play Store on Android Wear, to be eligible for merchandising on the homepage, and to be remotely installed from the web to the watch. As a result, we strongly recommend that developers move to multi-APK.

More additions in Developer Preview 4

Action and Navigation Drawers : An enhancement to peeking behavior allows the user to take action without scrolling all the way to the top or bottom of a list. Developers can further fine-tune drawer peeking behavior through new APIs, such as setShouldPeekOnScrollDown for the action drawer.

An enhancement to peeking behavior allows the user to take action without scrolling all the way to the top or bottom of a list. Developers can further fine-tune drawer peeking behavior through new APIs, such as for the action drawer. WearableRecyclerView : The curved layout is now opt-in, and with this, the WearableRecyclerView is now a drop-in replacement for RecyclerView.

The curved layout is now opt-in, and with this, the WearableRecyclerView is now a drop-in replacement for RecyclerView. Burn-in protection icon for complications: Complication data providers can now provide icons for use on screens susceptible to burn-in. These burn-in-safe icons are normally the outline of the icon in interactive mode. Previously, watch faces may have chosen not to display the icon at all in ambient mode to prevent screen burn-in.

Feedback welcome!

Thanks for all your terrific feedback on Android Wear 2.0. Check out g.co/wearpreview for the latest builds and documentation, keep the feedback coming by filing bugs or posting in our Android Wear Developers community, and stay tuned for Android Wear Developer Preview 5!