Android 8.1 Oreo: Go edition and on-device ML

Android 8.1 Oreo is the release that made Android fit phones with 1 GB of RAM or less. It shipped the Android Oreo (Go edition) configuration and the Neural Networks API, which runs machine-learning models on the device. For developers it was a small API level on top of Android 8.0, with no new permissions.

At a glance

The first developer preview, on 25 October 2017, already carried the final API level 27, and Play opened to apps targeting it that day. Google announced the final release at Google for India on Monday 4 December and posted the details on 5 December, with the update “rolling out” to Pixel and Nexus “over the next week”. MobileSyrup reported the rollout the same day. Partner devices, including Go edition phones, were promised “in the months ahead”. The two previews have their own parts below: Developer Preview 1 and Developer Preview 2.

What it brought

• Android Oreo (Go edition). A configuration for entry-level phones with 1 GB of RAM or less: platform memory savings, rebuilt Google apps that use less memory, storage and data, and new hardware feature constants so Play can target low-RAM or normal devices. The 8.1 CDD makes a handheld with 1 GB or less declare android.hardware.ram.low. The first Go edition phones, among them the Alcatel 1X, Nokia 1 and ZTE Tempo Go, were announced at Mobile World Congress on 27 February 2018. Google said the configuration leaves twice as much storage free out of the box.
• Neural Networks API. A C API in the NDK for hardware-accelerated inference. Google built it as the base layer for TensorFlow Lite, Caffe2 and other frameworks, starting with vision models such as MobileNets and Inception v3.
• Autofill updates. BaseAdapter.setAutofillOptions() gives a spinner’s values as strings, for example the years of a card expiry. AutofillManager.notifyViewVisibilityChanged() reports visibility changes in virtual views. Autofill services can add a CustomDescription and a Validator (LuhnChecksumValidator, RegexValidator) to the save UI.
• SharedMemory. android.os.SharedMemory creates and maps anonymous shared memory, sets read or write protection, and is Parcelable, so it passes to another process through AIDL. It works with ASharedMemory in the NDK.
• WallpaperColors. A live wallpaper can tell the system UI its primary, secondary and tertiary colours, and call notifyColorsChanged() when they change.
• Video thumbnails. MediaMetadataRetriever.getScaledFrameAtTime() returns a frame scaled to a given size. Google’s example: a frame from a 4K video through getFrameAtTime() is a 16 MB bitmap.
• Lock screen activities. Activity.setShowWhenLocked() and setTurnScreenOn() replace the window flags of the same purpose.
• Pixel Visual Core. On Pixel 2, 8.1 enabled Google’s image co-processor through a new developer option, so apps using the Camera API could take HDR+ shots through it.
• User-visible. Wi-Fi settings label open networks by speed, from “Slow” to “Very Fast”; Android Police reported the labels reaching users in January 2018. Bluetooth settings show a connected device’s battery, as in “Connected, battery 80%”. Both strings first appear in AOSP at 8.1.
• Dimmed navigation buttons. After 2.25 seconds without a touch, SystemUI fades the back, home and recents buttons to 60% opacity, except when the wallpaper is visible behind the bar. In 8.0 the buttons dimmed only when an app asked for low-profile mode. Android Police spotted it in the first preview and read it as a guard against burn-in; Google gave no reason.

Security and privacy

• Conscrypt first. New algorithms (GCM parameters, AES, DESede and HMAC key generators, NONEWITHECDSA) were implemented in Conscrypt, which is now preferred over Bouncy Castle.
• Fewer trusted roots. The system CA store dropped many obsolete roots, including those of WoSign and StartCom, which Chrome had already distrusted in 2017.
• Safe Browsing in WebView. WebView.startSafeBrowsing() and WebViewClient.onSafeBrowsingHit() let an app decide what happens when a page is a known threat, instead of always showing the warning page.

• Fingerprint errors. FINGERPRINT_ERROR_LOCKOUT_PERMANENT (too many lockouts, until the user unlocks with PIN, pattern or password) and FINGERPRINT_ERROR_VENDOR became public. In 8.0 they were @hide.
• Patch level. The first 8.1 build, OPM1.171019.011, shipped with the 2017-12-05 security patch level.

Permissions

Android 8.1 added no new Manifest.permission constants and changed no grants. The permission model is the one from Android 8.0.

One limit is tied to Go devices: on a phone where ActivityManager.isLowRamDevice() returns true, NotificationListenerService and ConditionProviderService are not supported, so there is no notification access for the user to grant.

What changed for your app

All apps on Android 8.1

Apps targeting API 27

The two targeting rules in the first rows come from the AOSP documentation of O_MR1 in Build.java. developer.android.com has no separate behaviour-changes page for 8.1.

What lasted

• Android Go continued as a configuration for low-RAM phones, and FEATURE_RAM_LOW is still how Play targets them.
• The Neural Networks API shipped on every device from 8.1 on, and was deprecated in Android 15. Google now points to alternatives such as the TensorFlow Lite GPU runtime.
• Fingerprint: Android 9 moved apps from FingerprintManager to BiometricPrompt.
• Play’s target-API rule skipped 27: new apps needed API 26 from August 2018, and API 28 from August 2019 (updates from November of each year).
• SharedMemory and WallpaperColors are still in the SDK.

Worth knowing

• The O_MR1 constant shipped with a two-word comment: O MR1. Today’s AOSP adds “Released publicly as Android 8.1 in December 2017.”
• On Android 8.0 itself, Activity.onCreate() threw an IllegalStateException for apps targeting above 26 (that is, 27) when a translucent or floating activity fixed its orientation. Its message: “Only fullscreen opaque activities can request orientation”. The 8.1 Activity.java no longer has that throw.
• 8.1 redrew the Easter egg logo: a dark cookie with a white cream layer replaced 8.0’s amber circles. The octopus behind it is unchanged, and Android Police noted it still has eight legs for 8.1.