Behavior Changes

Along with new features and capabilities, the M Developer Preview includes a variety of system changes and API behavior changes. This document highlights some of the key changes that you should understand and account for in your apps.

If you have previously published an app for Android, be aware that these changes in the platform affect your app.

Runtime Permissions

This preview introduces a new permissions model, where users can now directly manage app permissions at runtime. This model gives users improved visibility and control over permissions, while streamlining the installation and auto-update processes for app developers. Users can grant or revoke permissions individually for installed apps.

On your apps that target the M Preview release or higher, make sure to check for and request permissions at runtime. To determine if your app has been granted a permission, call the new checkSelfPermission() method. To request a permission, call the new requestPermissions() method. Even if your app is not targeting the M Preview release, you should test your app under the new permissions model.

For details on supporting the new permissions model in your app, see the Permissions developer preview page. For tips on how to assess the impact on your app, see the Testing Guide

Power-Saving Optimizations

This preview introduces new power-saving optimizations for idle devices and apps.

  • Doze: If a user unplugs a device and leaves it stationary, with its screen off, for a period of time, the device goes into Doze mode, where it attempts to keep the system in a sleep state. In this mode, devices periodically resume normal operations for brief periods of time so that app syncing can occur and the system can perform any pending operations.
  • App Standby: App Standby allows the system to determine that an app is idle when the user is not actively using it. The system makes this determination when the user does not touch the app for a certain period of time. If the device is unplugged, the system disables network access and suspends syncs and jobs for the apps it deems idle.

To learn more about these power-saving changes, see Power-Saving Optimizations.

Adoptable Storage Devices

With this preview, users can adopt external storage devices such as SD cards. Adopting an external storage device encrypts and formats the device to behave like internal storage. This feature allows users to move both apps and private data of those apps between storage devices. When moving apps, the system respects the android:installLocation preference in the manifest.

If your app accesses the following APIs or fields, be aware that the file paths they return will dynamically change when the app is moved between internal and external storage devices. When building file paths, it is strongly recommended that you always call these APIs dynamically. Don’t use hardcoded file paths or persist fully-qualified file paths that were built previously.

To debug this feature in the developer preview, you can enable adoption of a USB drive that is connected to an Android device through a USB On-The-Go (OTG) cable, by running this command:

$ adb shell sm set-force-adoptable true

Apache HTTP Client Removal

This preview removes support for the Apache HTTP client. If your app is using this client and targets Android 2.3 (API level 9) or higher, use the HttpURLConnection class instead. This API is more efficient because it reduces network use through transparent compression and response caching, and minimizes power consumption. To continue using the Apache HTTP APIs, you must first declare the following compile-time dependency in your build.gradle file: 

android {
    useLibrary 'org.apache.http.legacy'
}

Android is moving away from OpenSSL to the BoringSSL library. If you’re using the Android NDK in your app, don't link against cryptographic libraries that are not a part of the NDK API, such as libcrypto.so and libssl.so. These libraries are not public APIs, and may change or break without notice across releases and devices. In addition, you may expose yourself to security vulnerabilities. Instead, modify your native code to call the Java cryptography APIs via JNI or to statically link against a cryptography library of your choice.

AudioManager Changes

Setting the volume directly or muting specific streams via the AudioManager class is no longer supported. The setStreamSolo() method is deprecated, and you should call the requestAudioFocus() method instead. Similarly, the setStreamMute() method is deprecated; instead, call the adjustStreamVolume() method and pass in the direction value ADJUST_MUTE or ADJUST_UNMUTE.

Notifications

This release removes the Notification.setLatestEventInfo() method. Use the Notification.Builder class instead to construct notifications. To update a notification repeatedly, reuse the Notification.Builder instance. Call the build() method to get updated Notification instances.

The adb shell dumpsys notification command no longer prints out your notification text. Use the adb shell dumpsys notification --noredact command instead to print out the text in a notification object.

Text Selection

When users select text in your app, you can now display text selection actions such as Cut, Copy, and Paste in a floating toolbar. The user interaction implementation is similar to that for the contextual action bar, as described in Enabling the contextual action mode for individual views.

To implement a floating toolbar for text selection, make the following changes in your existing apps:

  1. In your View or Activity object, change your ActionMode calls from startActionMode(Callback) to startActionMode(Callback, ActionMode.TYPE_FLOATING).
  2. Take your existing implementation of ActionMode.Callback and make it extend ActionMode.Callback2 instead.
  3. Override the onGetContentRect() method to provide the coordinates of the content Rect object (such as a text selection rectangle) in the view.
  4. If the rectangle positioning is no longer valid, and this is the only element to be invalidated, call the invalidateContentRect() method.

If you are using Android Support Library revision 22.2, be aware that floating toolbars are not backward-compatible and appcompat takes control over ActionMode objects by default. This prevents floating toolbars from being displayed. To enable ActionMode support in an AppCompatActivity, call getDelegate(), then call setHandleNativeActionModesEnabled() on the returned AppCompatDelegate object and set the input parameter to false. This call returns control of ActionMode objects to the framework. In devices running the M Preview, that allows the framework to support ActionBar or floating toolbar modes, while on pre-M Preview devices, only the ActionBar modes are supported.

Android Keystore Changes

With this preview, the Android Keystore provider no longer supports DSA. ECDSA is still supported.

Keys which do not require encryption at rest will no longer be deleted when secure lock screen is disabled or reset (for example, by the user or a Device Administrator). Keys which require encryption at rest will be deleted during these events.

Wi-Fi and Networking Changes

This preview introduces the following behavior changes to the Wi-Fi and networking APIs.

  • Your apps can now change the state of WifiConfiguration objects only if you created these objects. You are not permitted to modify or delete WifiConfiguration objects created by the user or by other apps.
  • Previously, if an app forced the device to connect to a specific Wi-Fi network by using enableNetwork() with the disableAllOthers=true setting, the device disconnected from other networks such as cellular data. In this preview, the device no longer disconnects from such other networks. If your app’s targetSdkVersion is “20” or lower, it is pinned to the selected Wi-Fi network. If your app’s targetSdkVersion is “21” or higher, use the multinetwork APIs (such as openConnection(), bindSocket(), and the new bindProcessToNetwork() method) to ensure that its network traffic is sent on the selected network.

Camera Service Changes

In this preview, the model for accessing shared resources in the camera service has been changed from the previous “first come, first serve” access model to an access model where high-priority processes are favored. Changes to the service behavior include:

  • Access to camera subsystem resources, including opening and configuring a camera device, is awarded based on the “priority” of the client application process. Application processes with user-visible or foreground activities are generally given a higher-priority, making camera resource acquisition and use more dependable.
  • Active camera clients for lower priority apps may be “evicted” when a higher priority application attempts to use the camera. In the deprecated Camera API, this results in onError() being called for the evicted client. In the Camera2 API, it results in onDisconnected() being called for the evicted client.
  • On devices with appropriate camera hardware, separate application processes are able to independently open and use separate camera devices simultaneously. However, multi-process use cases, where simultaneous access causes significant degradation of performance or capabilities of any of the open camera devices, are now detected and disallowed by the camera service. This change may result in “evictions” for lower priority clients even when no other app is directly attempting to access the same camera device.
  • Changing the current user causes active camera clients in apps owned by the previous user account to be evicted. Access to the camera is limited to user profiles owned by the current device user. In practice, this means that a “Guest” account, for example, will not be able to leave running processes that use the camera subsystem when the user has switched to a different account.

Runtime

The ART runtime now properly implements access rules for the newInstance() method. This change fixes a problem where Dalvik was checking access rules incorrectly in previous versions. If your app uses the newInstance() method and you want to override access checks, call the setAccessible() method with the input parameter set to true. If your app uses the v7 appcompat library or the v7 recyclerview library, you must update your app to use to the latest versions of these libraries. Otherwise, make sure that any custom classes referenced from XML are updated so that their class constructors are accessible.

This preview updates the behavior of the dynamic linker. The dynamic linker now understands the difference between a library’s soname and its path ( public bug 6670), and search by soname is now implemented. Apps which previously worked that have bad DT_NEEDED entries (usually absolute paths on the build machine’s file system) may fail when loaded.

The dlopen(3) RTLD_LOCAL flag is now correctly implemented. Note that RTLD_LOCAL is the default, so calls to dlopen(3) that didn’t explicitly use RTLD_LOCAL will be affected (unless your app explicitly used RTLD_GLOBAL). With RTLD_LOCAL, symbols will not be made available to libraries loaded by later calls to dlopen(3) (as opposed to being referenced by DT_NEEDED entries).

Access to Hardware Identifier

To provide users with greater data protection, starting in this release, Android removes programmatic access to the device’s local hardware identifier for apps using the Wi-Fi and Bluetooth APIs. The WifiInfo.getMacAddress() and the BluetoothAdapter.getAddress() methods now return a constant value of 02:00:00:00:00:00.

To access the hardware identifiers of nearby external devices via Bluetooth and Wi-Fi scans, your app must now have the following permissions:

Note: When a device running M Developer Preview initiates a background Wi-Fi or Bluetooth scan, the operation is visible to external devices as originating from a randomized MAC address.

APK Validation

The platform now performs stricter validation of APKs. An APK is considered corrupt if a file is declared in the manifest but not present in the APK itself. An APK must be re-signed if any of the contents are removed.

USB Connection

Device connections through the USB port are now set to charge-only mode by default. To access the device and its content over a USB connection, users must explicitly grant permission for such interactions. If your app supports user interactions with the device over a USB port, take into consideration that the interaction must be explicitly enabled.

Android for Work Changes

This preview includes the following behavior changes for Android for Work:

  • Work contacts in personal contexts. The Google Dialer Call Log now displays work contacts when the user views past calls. Setting setCrossProfileCallerIdDisabled() to true hides the work profile contacts in the Google Dialer Call Log. Work contacts can be displayed along with personal contacts to devices over Bluetooth only if you set setBluetoothContactSharingDisabled() to false. By default, it is set to true.
  • Wi-Fi configuration removal: Wi-Fi configurations added by a Profile Owner (for example, through calls to the addNetwork() method) are now removed if that work profile is deleted.
  • Wi-Fi configuration lockdown: Any Wi-Fi configuration created by an active Device Owner can no longer be modified or deleted by the user if WIFI_DEVICE_OWNER_CONFIGS_LOCKDOWN is non-zero. The user can still create and modify their own Wi-Fi configurations. Active Device Owners have the privilege of editing or removing any Wi-Fi configurations, including those not created by them.
  • Download Work Policy Controller via Google account addition: When a Google account that requires management via a Work Policy Controller (WPC) app is added to a device outside of a managed context, the add account flow now prompts the user to install the appropriate WPC. This behavior also applies to accounts added via Settings > Accounts and in the initial device setup wizard.
  • Changes to specific DevicePolicyManager API behaviors:
  • Changes to other APIs:
    • Data Usage: The android.app.usage.NetworkUsageStats class has been renamed NetworkStats.
  • Changes to global settings:
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