Android 9 features and APIs

Android 9 (API level 28) introduces great new features and capabilities for users and developers. This document highlights what's new for developers.

To learn about the new APIs, read the API diff report or visit the Android API reference. Also be sure to check out Android 9 Behavior Changes to learn about areas where platform changes may affect your apps.

Indoor positioning with Wi-Fi RTT

Android 9 adds platform support for the IEEE 802.11mc Wi-Fi protocol—also known as Wi-Fi Round-Trip-Time (RTT)—to let you take advantage of indoor positioning in your apps.

On devices running Android 9 with hardware support, your apps can use the RTT APIs to measure the distance to nearby RTT-capable Wi-Fi access points (APs). The device must have location services enabled and Wi-Fi scanning turned on (under Settings > Location), and your app must have the ACCESS_FINE_LOCATION permission. The device doesn't need to connect to the access points to use RTT. To maintain privacy, only the phone is able to determine the distance to the access point; the access points do not have this information.

If your device measures the distance to 3 or more access points, you can use a multilateration algorithm to estimate the device position that best fits those measurements. The result is typically accurate within 1 to 2 meters.

With this accuracy, you can build new experiences, like in-building navigation and fine-grained location-based services, such as disambiguated voice control (for example, "Turn on this light") and location-based information (such as "Are there special offers for this product?").

See the WiFi RTT API in use in the Android WifiRttScan demo app.

For more information, see Wi-Fi location: ranging with RTT.

Display cutout support

Testing display cutout by using emulator

Android 9 offers support for the latest edge-to-edge screens that contain display cutouts for cameras and speakers. The DisplayCutout class lets you find out the location and shape of the non-functional areas where content shouldn't be displayed. To determine the existence and placement of these cutout areas, use the getDisplayCutout() method.

A new window layout attribute, layoutInDisplayCutoutMode, allows your app to lay out its content around a device's cutouts. You can set this attribute to one of the following values:

• LAYOUT_IN_DISPLAY_CUTOUT_MODE_DEFAULT
• LAYOUT_IN_DISPLAY_CUTOUT_MODE_SHORT_EDGES
• LAYOUT_IN_DISPLAY_CUTOUT_MODE_NEVER

You can simulate a screen cutout on any device or emulator running Android 9 as follows:

1. Enable developer options.
2. In the Developer options screen, scroll down to the Drawing section and select Simulate a display with a cutout.
3. Select the size of the cutout.

Notifications

Android 9 introduces several enhancements to notifications, all of which are available to developers targeting API level 28 and above.

MessagingStyle with photo attached.

MessagingStyle with replies and conversation.

For sample code that uses notifications, including Android 9 features, see the Android Notifications Sample.

Enhanced messaging experience

Starting in Android 7.0 (API level 24), you could add an action to reply to messages or enter other text directly from a notification. Android 9 enhances this feature with the following enhancements:

• Simplified support for conversation participants: The Person class is used to identify people involved in a conversation, including their avatars and URIs. Many other APIs, such as addMessage(), now leverage the Person class instead of a CharSequence. The Person class also supports the Builder design pattern.

• Support for images: Android 9 now displays images in Messaging Notifications on phones. You can use setData() on the message to display an image. The following code snippet demonstrates how to create a Person and a message containing an image.

// Create new Person.
val sender = Person()
        .setName(name)
        .setUri(uri)
        .setIcon(null)
        .build()
// Create image message.
val message = Message("Picture", time, sender)
        .setData("image/", imageUri)
val style = Notification.MessagingStyle(getUser())
        .addMessage("Check this out!", 0, sender)
        .addMessage(message)

// Create new Person.
Person sender = new Person()
        .setName(name)
        .setUri(uri)
        .setIcon(null)
        .build();
// Create image message.
Message message = new Message("Picture", time, sender)
        .setData("image/", imageUri);
Notification.MessagingStyle style = new Notification.MessagingStyle(getUser())
        .addMessage("Check this out!", 0, sender)
        .addMessage(message);

• Save replies as drafts: Your app can retrieve the EXTRA_REMOTE_INPUT_DRAFT sent by the system when a user inadvertently closes a messaging notification. You can use this extra to pre-populate text fields in the app so users can finish their reply.

• Identify if a conversation is a group conversation: You can use setGroupConversation() to purposefully identify a conversation as a group or non-group conversation.

• Set the semantic action for an intent: The setSemanticAction() method allows you to give semantic meaning to an action, such as "mark as read," "delete," "reply," and so on.

• SmartReply: Android 9 supports the same suggested replies available in your messaging app. Use RemoteInput.setChoices() to provide an array of standard responses to the user.

Channel settings, broadcasts, and Do Not Disturb

Android 8.0 introduced Notification Channels, allowing you to create a user-customizable channel for each type of notification you want to display. Android 9 simplifies notification channel settings with these changes:

• Blocking channel groups: Users can now block entire groups of channels within the notification settings for an app. You can use the isBlocked() method to identify when a group is blocked and, as a result, not send any notifications for channels in that group.

  Additionally, your app can query for current channel group settings using the new getNotificationChannelGroup() method.

• New broadcast intent types: The Android system now sends broadcast intents when the blocking state of notification channels and channel groups’ changes. The app that owns the blocked channel or group can listen for these intents and react accordingly. For further information on these intent actions and extras, refer to the updated constants list in the NotificationManager reference. For information on reacting to broadcast intents, refer to Broadcasts.

• NotificationManager.Policy has three new Do-Not-Disturb priority categories:

  • PRIORITY_CATEGORY_ALARMS prioritizes alarms.
  • PRIORITY_CATEGORY_MEDIA prioritizes sounds from media sources, such as media and voice navigation.
  • PRIORITY_CATEGORY_SYSTEM prioritizes system sounds.

• NotificationManager.Policy also has seven new Do-Not-Disturb constants you can use to suppress visual interruption:

  • SUPPRESSED_EFFECT_FULL_SCREEN_INTENT prevents the notification from launching full-screen activity.
  • SUPPRESSED_EFFECT_LIGHTS blocks notification lights.
  • SUPPRESSED_EFFECT_PEEK prevents notifications from sliding briefly into view ("peeking").
  • SUPPRESSED_EFFECT_STATUS_BAR prevents notifications from appearing in the status bar on devices that support status bars.
  • SUPPRESSED_EFFECT_BADGE blocks badges on on devices that support badging. For more information, refer to Modify a notification badge.
  • SUPPRESSED_EFFECT_AMBIENT blocks notifications on devices that support ambient displays.
  • SUPPRESSED_EFFECT_NOTIFICATION_LIST prevents notifications from appearing in the list view on devices that support a list view, such as notification shade or lockscreen.

Multi-camera support and camera updates

On devices running Android 9, you can access streams simultaneously from two or more physical cameras. On devices with either dual-front or dual-back cameras, you can create innovative features not possible with just a single camera, such as seamless zoom, bokeh, and stereo vision. The API also lets you call a logical or fused camera stream that automatically switches between two or more cameras.

Other improvements in camera include additional Session parameters that help to reduce delays during initial capture, and surface sharing that lets camera clients handle various use cases without the need to stop and start camera streaming. We've also added APIs for display-based flash support and access to OIS timestamps for app-level image stabilization and special effects.

In Android 9 the multi-camera API supports monochrome cameras for devices with FULL or LIMITED capability. Monochrome output is achieved via the YUV_420_888 format with Y as grayscale, U (Cb) as 128, and V (Cr) as 128.

Android 9 also enables support for external USB/UVC cameras on supported devices.

ImageDecoder for drawables and bitmaps

Android 9 introduces the ImageDecoder class, which provides a modernized approach for decoding images. Use this class instead of the BitmapFactory and BitmapFactory.Options APIs.

ImageDecoder lets you create a Drawable or a Bitmap from a byte buffer, a file, or a URI. To decode an image, first call createSource() with the source of the encoded image. Then, call decodeDrawable() or decodeBitmap() by passing the ImageDecoder.Source object to create a Drawable or a Bitmap. To change the default settings, pass OnHeaderDecodedListener to decodeDrawable() or decodeBitmap(). ImageDecoder calls onHeaderDecoded() with the image's default width and height, once they are known. If the encoded image is an animated GIF or WebP, decodeDrawable() returns a Drawable that is an instance of the AnimatedImageDrawable class.

There are different methods you can use to set image properties:

• To scale the decoded image to an exact size, pass the target dimensions into setTargetSize(). You can also scale images using a sample size. Pass the sample size directly to setTargetSampleSize().
• To crop an image within the range of the scaled image, call setCrop().
• To create a mutable bitmap, pass true into setMutableRequired().

ImageDecoder also lets you add customized and complicated effects to an image such as rounded corners or circle masks. Use setPostProcessor() with an instance of the PostProcessor class to execute whatever drawing commands you want.

Animation

Android 9 introduces the AnimatedImageDrawable class for drawing and displaying GIF and WebP animated images. AnimatedImageDrawable works similarly to AnimatedVectorDrawable in that the render thread drives the animations of AnimatedImageDrawable. The render thread also uses a worker thread to decode, so that decoding does not interfere with other operations on the render thread. This implementation allows your app to display an animated image without managing its updates or interfering with other events on your app's UI thread.

An AnimatedImageDrawable can be decoded using an instance of ImageDecoder. The following code snippet shows how to use ImageDecoder to decode your AnimatedImageDrawable:

@Throws(IOException::class)
private fun decodeImage() {
    val decodedAnimation = ImageDecoder.decodeDrawable(
        ImageDecoder.createSource(resources, R.drawable.my_drawable))

    // Prior to start(), the first frame is displayed.
    (decodedAnimation as? AnimatedImageDrawable)?.start()
}

private void decodeImage() throws IOException {
    Drawable decodedAnimation = ImageDecoder.decodeDrawable(
        ImageDecoder.createSource(getResources(), R.drawable.my_drawable));

    if (decodedAnimation instanceof AnimatedImageDrawable) {
        // Prior to start(), the first frame is displayed.
        ((AnimatedImageDrawable) decodedAnimation).start();
    }
}

ImageDecoder has several methods allowing you to further modify the image. For example, you can use the setPostProcessor() method to modify the appearance of the image, such as applying a circle mask or rounded corners.

HDR VP9 Video, HEIF image compression, and Media APIs

Android 9 provides built-in support for High Dynamic Range (HDR) VP9 Profile 2, so you can deliver HDR-enabled movies to your users from YouTube, Play Movies, and other sources on HDR-capable devices.

Android 9 also adds support for encoding images using the High Efficiency Image File format (HEIF or HEIC), which improves compression and reduces storage space and network data usage. HEIF still image samples are supported in the MediaMuxer and MediaExtractor classes. With platform support on Android 9 devices, it's easy to send and utilize HEIF images from your backend server. After you've made sure that your app is compatible with this data format for sharing and display, give HEIF a try as an image storage format in your app. You can do a jpeg-to-heic conversion using ImageDecoder or BitmapFactory (which obtains a bitmap from a JPEG file). You can then use HeifWriter to write HEIF still images from YUV byte buffers, or instances of Surface or Bitmap.

Media metrics are also available from the AudioTrack, AudioRecord, and MediaDrm classes.

Android 9 introduces methods to the MediaDRM class to get metrics, HDCP levels, security levels, and number of sessions, and to add more control over security levels and secure stops. See the API Diff report for details.

In Android 9, the AAudio API adds support for several additional AAudioStream attributes, including usage, content type, and input preset. Using these attributes, you can create streams that are tuned for VoIP or camcorder applications. You can also set the session ID to associate an AAudio stream with a submix that can include effects. Use the AudioEffect API to control the effects.

Android 9 introduces the AudioEffect API for dynamics processing. With this class, you can build channel-based audio effects—including equalization, multi-band compression, and limiter—across multiple stages. The number of bands and active stages is configurable, and most parameters can be controlled in real time.

Data cost sensitivity in JobScheduler

Beginning in Android 9, JobScheduler can use network status signals provided by carriers to improve the handling of network-related jobs.

Jobs can declare their estimated data size, signal prefetching, and specify detailed network requirements. JobScheduler then manages work according to the network status. For example, when the network signals that it is congested, JobScheduler might defer large network requests. When on an unmetered network, JobScheduler can run prefetch jobs to improve the user experience, such as by prefetching headlines.

When adding jobs, make sure to use setEstimatedNetworkBytes(), setPrefetch(), and setRequiredNetwork() when appropriate to help JobScheduler handle the work properly. When your job executes, be sure to use the Network object returned by JobParameters.getNetwork(). Otherwise you'll implicitly use the device’s default network which may not meet your requirements, causing unintended data usage.

Neural Networks API 1.1

The Neural Networks API was introduced in Android 8.1 (API level 27) to accelerate on-device machine learning on Android. Android 9 expands and improves the API, adding support for nine new operations:

• Element-wise mathematical operations:
  • ANEURALNETWORKS_DIV
  • ANEURALNETWORKS_SUB
• Array operations:
  • ANEURALNETWORKS_BATCH_TO_SPACE_ND
  • ANEURALNETWORKS_SPACE_TO_BATCH_ND
  • ANEURALNETWORKS_SQUEEZE
  • ANEURALNETWORKS_STRIDED_SLICE
  • ANEURALNETWORKS_TRANSPOSE
  • ANEURALNETWORKS_PAD
  • ANEURALNETWORKS_MEAN

Known issue: When passing ANEURALNETWORKS_TENSOR_QUANT8_ASYMM tensors to the ANEURALNETWORKS_PAD operation, which is available on Android 9 and higher, the output from NNAPI may not match output from higher-level machine learning frameworks, such as TensorFlow Lite. You should instead pass only ANEURALNETWORKS_TENSOR_FLOAT32 until the issue is resolved.

Additionally, the API also introduces a new function, ANeuralNetworksModel_relaxComputationFloat32toFloat16(), that allows you to specify whether to calculate ANEURALNETWORKS_TENSOR_FLOAT32 with a range and precision as low as that of the IEEE 754 16-bit floating-point format.

Autofill framework

Android 9 introduces multiple improvements that autofill services can implement to further enhance the user experience when filling out forms. To learn more about how to use autofill features in your app, see the Autofill Framework guide.

Security enhancements

Android 9 introduces a number of security features, which the following sections summarize:

Android Protected Confirmation

Supported devices that run Android 9 or higher give you the ability to use Android Protected Confirmation. When using this workflow, your app displays a prompt to the user, asking them to approve a short statement. This statement allows the app to reaffirm that the user would like to complete a sensitive transaction, such as making a payment.

If the user accepts the statement, Android Keystore receives and stores a cryptographic signature that's protected by a keyed-hash message authentication code (HMAC). After Android Keystore confirms the message's validity, your app can use the key generated from trustedConfirmationRequired in the trusted execution environment (TEE) to sign the message that the user accepted. The signature indicates, with very high confidence, that the user has seen the statement and has agreed to it.

Caution: Android Protected Confirmation doesn't provide a secure information channel for the user. Your app cannot assume any confidentiality guarantees beyond those that the Android platform offers. In particular, don't use this workflow to display sensitive information that you wouldn't ordinarily show on the user's device.

For guidance on adding support for Android Protected Confirmation, see the Android Protected Confirmation guide.

Unified biometric authentication dialog

In Android 9, the system provides biometric authentication dialogs on behalf of your app. This functionality creates a standardized look, feel, and placement for the dialog, giving users more confidence that they're authenticating against a trusted biometric credential checker.

If your app uses FingerprintManager to display a fingerprint authentication dialog to users, switch to using BiometricPrompt instead. BiometricPrompt relies on the system to display the authentication dialog. It also changes its behavior to adapt to the type of biometric authentication that a user has chosen.

Hardware security module

Supported devices running Android 9 or higher installed can have a StrongBox Keymaster, an implementation of the Keymaster HAL that resides in a hardware security module. The module contains the following:

• Its own CPU.
• Secure storage.
• A true random-number generator.
• Additional mechanisms to resist package tampering and unauthorized sideloading of apps.

When checking keys stored in the StrongBox Keymaster, the system corroborates a key's integrity with the Trusted Execution Environment (TEE).

To learn more about using Strongbox Keymaster, see Hardware Security Module.

Secure key import into Keystore

Android 9 provides additional key decryption security by adding the ability to import encrypted keys securely into the Keystore using an ASN.1‑encoded key format. The Keymaster then decrypts the keys in the Keystore, so the content of the keys never appears as plaintext in the device's host memory.

Learn more about how to Import encrypted keys more securely.

APK signature scheme with key rotation

Android 9 adds support for APK Signature Scheme v3. This scheme has the option to include a proof-of-rotation record in its signing block for each signing certificate. This capability enables your app to be signed with a new signing certificate by linking the APK file's past signing certificates to the one with which it is now signed.

Learn more on how to rotate keys using apksigner.

Option to allow key decryption only on unlocked devices

Android 9 introduces the unlockedDeviceRequired flag. This option determines whether the Keystore requires the screen to be unlocked before allowing decryption of any in-flight or stored data using the specified key. These types of keys are well suited for encrypting sensitive data to store on disk, such as health or enterprise data. The flag provides users a higher assurance that the data cannot be decrypted while the device is locked should their phone be lost or stolen.

To keep a key safe from decryption while the device is locked, enable the flag by passing true to the setUnlockedDeviceRequired() method. After completing this step, when the user's screen is locked, any attempts to decrypt or sign data using this key fail. A locked device requires a PIN, password, fingerprint, or some other trusted factor before it can be accessed.

Legacy encryption support

Android 9 devices that ship with Keymaster 4 support the Triple Data Encryption Algorithm, or Triple DES. If your app interoperates with legacy systems that require Triple DES, use this type of cipher when encrypting sensitive credentials.

To learn more about how to make your app more secure, see Security for Android Developers.

Deprecation of WPS

Wi-Fi Protected Setup (WPS) is deprecated for security reasons.

• The user has enabled backup using Android 9 or higher.
• The user has set a screen lock for their device that requires a PIN, pattern, or password to unlock.

When this privacy measure is enabled, the device's PIN, pattern, or password is required to restore data from the backups made by the user's device. To learn more about the technology behind this feature, see the Google Cloud Key Vault Service whitepaper.

Define device conditions required for backup

If your app data includes sensitive information or preferences, Android 9 gives you the ability to define the device conditions under which your app's data is included in the user's backup, such as when client-side encryption is enabled or a local device-to-device transfer is taking place.

To learn more about backing up data on Android devices, see Data Backup Overview.

Accessibility

Android 9 introduces enhancements to the accessibility framework that make it easier to provide even better experiences to users of your app.

Navigation semantics

Attributes added in Android 9 make it easier for you to define how accessibility services, especially screen readers, navigate from one part of the screen to another. These attributes can help users who are visually impaired quickly move through text in your app's UI and allow them to make a selection.

For example, in a shopping app, a screen reader can help users navigate directly from one category of deals to the next, without the screen reader having to read all items in a category before moving on to the next.

Accessibility pane titles

In Android 8.1 (API level 27) and lower, accessibility services cannot always determine when a specific pane of the screen was updated, such as when an activity replaces one fragment with another fragment. Panes consist of logically-grouped, visually-related UI elements that typically comprise a fragment.

In Android 9, you can provide accessibility pane titles, or individually identifiable titles, for these panes. If a pane has an accessibility pane title, accessibility services receive more detailed information when the pane changes. This capability allows services to provide more granular information to the user about what's changed in the UI.

To specify the title of a pane, use the android:accessibilityPaneTitle attribute. You can also update the title of a UI pane that is replaced at runtime using setAccessibilityPaneTitle(). For example, you could provide a title for the content area of a Fragment object.

Heading-based navigation

If your app displays textual content that includes logical headings, set the android:accessibilityHeading attribute to true for the instances of View that represent those headings. By adding these headings, you allow accessibility services to help users navigate directly from one heading to the next. Any accessibility service can use this capability to improve users' UI navigation experience.

Group navigation and output

Screen readers have traditionally used the android:focusable attribute to determine when they should read a ViewGroup, or a collection of View objects, as a single unit. That way, users could understand that the views were logically related to each other.

In Android 8.1 and lower, you need to mark each View object within a ViewGroup as non-focusable and the ViewGroup itself as focusable. This arrangement caused some instances of View to be marked focusable in a way that made keyboard navigation more cumbersome.

Starting in Android 9, you can use the android:screenReaderFocusable attribute in place of the android:focusable attribute in situations where making a View object focusable has undesirable consequences. Screen readers place focus on all elements that have set either android:screenReaderFocusable or android:focusable to true.

Convenience actions

Android 9 adds support for performing convenience actions on behalf of users:

Interaction with tooltips

Added features in the accessibility framework give you access to tooltips in an app's UI. Use getTooltipText() to read the text of a tooltip, and use the ACTION_SHOW_TOOLTIP and ACTION_HIDE_TOOLTIP to instruct instances of View to show or hide their tooltips.

Added global actions

Android 9 introduces support for two additional device actions in the AccessibilityService class. Your service can help users lock their devices and take screenshots using the GLOBAL_ACTION_LOCK_SCREEN and GLOBAL_ACTION_TAKE_SCREENSHOT actions, respectively.

Window change details

Android 9 makes it easier to track updates to an app's windows when an app redraws multiple windows simultaneously. When a TYPE_WINDOWS_CHANGED event occurs, use the getWindowChanges() API to determine how the windows have changed. During a multiwindow update, each window produces its own set of events. The getSource() method returns the root view of the window associated with each event.

If an app has defined accessibility pane titles for its View objects, your service can recognize when the app's UI is updated. When a TYPE_WINDOW_STATE_CHANGED event occurs, use the types returned by getContentChangeTypes() to determine how the window has changed. For example, the framework can detect when a pane has a new title, or when a pane has disappeared.

Rotation

To eliminate unintentional rotations, we've added a mode that pins the current orientation even if the device position changes. Users can trigger rotation manually when needed by pressing a button in the system bar.

The compatibility impacts for apps are minimal in most cases. However, if your app has any customized rotation behavior or uses any unusual screen orientation settings, you might run into issues that would have gone unnoticed before, when user rotation preference was always set to portrait. We encourage you to take a look at the rotation behavior in all the key activities of your app and make sure that all of your screen orientation settings are still providing the optimal experience.

For more details, see the associated behavior changes.

A new rotation mode lets users trigger rotation manually when needed using a button in the system bar.

Text

Android 9 brings the following text-related features to the platform:

• Precomputed Text: The PrecomputedText class improves text-rendering performance by enabling you to compute and cache the required information ahead of time. It also enables your app to perform text layout off the main thread.

• Magnifier: The Magnifier class is a platform widget that provides a magnifier API, allowing for a consistent magnifier-feature experience across all apps.

• Smart Linkify: Android 9 enhances the TextClassifier class, which leverages machine learning to identify some entities in selected text and suggest actions. For example, TextClassifier can enable your app to detect that the user has selected a phone number. Your app could then suggest that the user make a phone call using that number. The features in TextClassifier replace the functionality of the Linkify class.

• Text Layout: Several convenience methods and attributes make it easier to implement your UI design. For details, see the reference documentation for TextView.

ART ahead-of-time conversion of DEX files

On devices running Android 9 or higher, the Android runtime (ART) ahead-of-time compiler further optimizes compressed Dalvik Executable format (DEX) files by converting the DEX files in an app package into a more compact representation. This change allows your app to start faster and consume less disk space and RAM.

This improvement particularly benefits low-end devices with slower disk I/O speeds.

On-device system tracing

Android 9 allows you to record system traces from your device, then share a report of these recordings with your development team. This report supports multiple formats, including HTML.

By collecting these traces, you can capture timing data related to your app's processes and threads and view other types of globally-significant device states.

To learn more about this tool, see Perform on-device system tracing.