Google has released the Wear OS by Google developer preview and brought most of Android P features to wearables. The developer preview includes updated system images on the official Android Emulator and a downloadable system image for the Huawei Watch 2 Bluetooth or Huawei Watch 2 Classic Bluetooth. Google says that the initial release is intended for developers only and is not for daily or consumer use. Therefore, it can only be experienced via the manual download and flash method.
In the first developer release, there are certain features that developers should pay attention to while coding apps:
Restriction related to non-SDK methods and fields: To improve app compatibility, Android P has started the process of restricting access to non-SDK methods and fields. Therefore, Google advises developers to migrate away from these old methods.
Dark UI system theme: To enhance ‘glanceability’, Wear OS has switched to a UI theme with a darker/black background for the notifications stream and system launcher since the start of the year. This is now also the default for the system theme and should improve the legibility for Wear apps.
Limited background activity: To improve power, apps will no longer be allowed to run in the background unless the watch is on the charger. Wear OS is going further with Android's app standby feature than some other form factors, however, exceptions to this include watch faces and complications that the user currently has selected. This feature will be rolled out gradually in the developer preview, so one may not see it immediately on his/her device.
Turning off radios when off body: To improve power, Bluetooth, Wi-Fi, and cellular radios will be turned off when the watch is detected to be off-body for an extended period of time. This is another feature that will be rolled out gradually. However, developers can choose to ignore this if their apps require to access the radios for critical functions.
Wi-Fi off when BT is disconnected: To improve power, the device will no longer automatically connect to Wi-Fi when disconnected from Bluetooth. However, there are exceptions if an app is requesting a high bandwidth network or if the smartwatch is on the charger. This feature too will be rolled out gradually.
(source)
