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Tuesday, 29 September 2015

Android 5.0 Behavior Changes

Android 5.0 Behavior Changes


API Level: 21
Along with new features and capabilities, Android 5.0 includes a variety of system changes and API behavior changes. This document highlights some of the key changes that you should be understand and account for in your apps.
If you have previously published an app for Android, be aware that your app might be affected by these changes in Android 5.0.
For a high-level look at the new platform features, instead see the Android Lollipop highlights.

Android Runtime (ART)

In Android 5.0 the ART runtime replaces Dalvik as the platform default. The ART runtime was introduced in Android 4.4 on an experimental basis.
For an overview of ART's new features, see Introducing ART. Some of the major new features are:
  • Ahead-of-time (AOT) compilation
  • Improved garbage collection (GC)
  • Improved debugging support
Most Android apps should just work without any changes under ART. However, some techniques that work on Dalvik do not work on ART. For information about the most important issues, see Verifying App Behavior on the Android Runtime (ART). Pay particular attention if:
  • Your app uses Java Native Interface (JNI) to run C/C++ code.
  • You use development tools that generate non-standard code (such as some obfuscators).
  • You use techniques that are incompatible with compacting garbage collection.

Notifications

Make sure your notifications take these Android 5.0 changes into account. To learn more about designing your notifications for Android 5.0 and higher, see the notifications design guide.

Material design style

Notifications are drawn with dark text atop white (or very light) backgrounds to match the new material design widgets. Make sure that all your notifications look right with the new color scheme. If your notifications look wrong, fix them:
  • Use setColor() to set an accent color in a circle behind your icon image.
  • Update or remove assets that involve color. The system ignores all non-alpha channels in action icons and in the main notification icon. You should assume that these icons will be alpha-only. The system draws notification icons in white and action icons in dark gray.

Sound and vibration

If you are currently adding sounds and vibrations to your notifications by using the Ringtone, MediaPlayer, orVibrator classes, remove this code so that the system can present notifications correctly in priority mode. Instead, useNotification.Builder methods to add sounds and vibration.
Setting the device to RINGER_MODE_SILENT causes the device to enter the new priority mode. The device leaves priority mode if you set it to RINGER_MODE_NORMAL or RINGER_MODE_VIBRATE.
Previously, Android used STREAM_MUSIC as the master stream to control volume on tablet devices. In Android 5.0, the master volume stream for both phone and tablet devices is now unified, and is controlled by STREAM_RING orSTREAM_NOTIFICATION.

Lock screen visibility

By default, notifications now appear on the user's lock screen in Android 5.0. Users can choose to protect sensitive information from being exposed, in which case the system automatically redacts the text displayed by the notification. To customize this redacted notification, use setPublicVersion().
If the notification does not contain personal information, or if you want to allow media playback control on the notification, call the setVisibility() method and set the notification's visibility level to VISIBILITY_PUBLIC.

Media playback

If you are implementing notifications that present media playback status or transport controls, consider using the newNotification.MediaStyle template instead of a custom RemoteViews.RemoteView object. Whichever approach you choose, make sure to set the notification's visibility to VISIBILITY_PUBLIC so that your controls are accessible from the lock screen. Note that beginning in Android 5.0, the system no longer shows RemoteControlClient objects on the lock screen. For more information, see If your app uses RemoteControlClient.

Heads-up notification

Notifications may now appear in a small floating window (also called a heads-up notification) when the device is active (that is, the device is unlocked and its screen is on). These notifications appear similar to the compact form of your notification, except that the heads-up notification also shows action buttons. Users can act on, or dismiss, a heads-up notification without leaving the current app.
Examples of conditions that may trigger heads-up notifications include:
  • The user's activity is in fullscreen mode (the app uses fullScreenIntent)
  • The notification has high priority and uses ringtones or vibrations
If your app implements notifications under any of those scenarios, make sure that heads-up notifications are presented correctly.

Media Controls and RemoteControlClient

The RemoteControlClient class is now deprecated. Switch to the new MediaSession API as soon as possible.
Lock screens in Android 5.0 do not show transport controls for your MediaSession or RemoteControlClient. Instead, your app can provide media playback control from the lock screen through a notification. This gives your app more control over the presentation of media buttons, while providing a consistent experience for users across locked and unlocked devices.
Android 5.0 introduces a new Notification.MediaStyle template for this purpose. Notification.MediaStyle converts notification actions that you added with Notification.Builder.addAction() into compact buttons embedded in your app's media playback notifications. Pass your session token to the setSession() method to inform the system that this notification controls an ongoing media session.
Make sure to set the notification's visibility to VISIBILITY_PUBLIC to mark the notification as safe to show on any lock screen (secure or otherwise). For more information, see Lock screen notifications.
To display media playback controls if your app is running on the Android TV or Wear platform, implement theMediaSession class. You should also implement MediaSession if your app needs to receive media button events on Android devices.

getRecentTasks()

With the introduction of the new concurrent documents and activities tasks feature in Android 5.0 (see Concurrent documents and activities in the recents screen below), the ActivityManager.getRecentTasks() method is now deprecated to improve user privacy. For backward compatibility, this method still returns a small subset of its data, including the calling application’s own tasks and possibly some other non-sensitive tasks (such as Home). If your app is using this method to retrieve its own tasks, use getAppTasks() instead to retrieve that information.

64-Bit Support in the Android NDK

Android 5.0 introduces support for 64-bit systems. The 64-bit enhancement increases address space and improves performance, while still supporting existing 32-bit apps fully. The 64-bit support also improves the performance of OpenSSL for cryptography. In addition, this release introduces new native media NDK APIs, as well as native OpenGL ES (GLES) 3.1 support.
To use the 64-bit support provided in Android 5.0, download and install NDK Revision 10c from the Android NDK page. Refer to the Revision 10c release notes for more information about important changes and bug fixes to the NDK.

Binding to a Service

The Context.bindService() method now requires an explicit Intent, and throws an exception if given an implicit intent. To ensure your app is secure, use an explicit intent when starting or binding your Service, and do not declare intent filters for the service.

WebView

Android 5.0 changes the default behavior for your app.
  • If your app targets API level 21 or higher:
    • The system blocks mixed content and third party cookies by default. To allow mixed content and third party cookies, use the setMixedContentMode() and setAcceptThirdPartyCookies() methods respectively.
    • The system now intelligently chooses portions of the HTML document to draw. This new default behavior helps to reduce memory footprint and increase performance. If you want to render the whole document at once, disable this optimization by calling enableSlowWholeDocumentDraw().
  • If your app targets API levels lower than 21: The system allows mixed content and third party cookies, and always renders the whole document at once.

Uniqueness Requirement for Custom Permissions

As documented in the Permissions overview, Android apps can define custom permissions as a means of managing access to components in a proprietary way, without using the platform’s pre-defined system permissions. Apps define custom permissions in <permission> elements declared in their manifest files.
There are a small number of scenarios where defining custom permissions is a legitimate and secure approach. However, creating custom permissions is sometimes unnecessary and can even introduce potential risk to an app, depending on the protection level assigned to the permissions.
Android 5.0 includes a behavior change to ensure that only one app can define a given custom permission, unless signed with the same key as other apps defining the permission.

Apps using duplicate custom permissions

Any app can define any custom permission it wants, so it can happen that multiple apps might define the same custom permission. For example, if two apps offer a similar capability, they might derive the same logical name for their custom permissions. Apps might also incorporate common public libraries or code examples that themselves include the same custom permission definitions.
In Android 4.4 and earlier, users were able to install multiple such apps on a given device, although the system assigned the protection level specified by the first-installed app.
Starting in Android 5.0, the system enforces a new uniqueness restriction on custom permissions for apps that are signed with different keys. Now only one app on a device can define a given custom permission (as determined by its name), unless the other app defining the permission is signed with the same key. If the user tries to install an app with a duplicate custom permission and is not signed with the same key as the resident app that defines the permission, the system blocks the installation.

Considerations for your app

In Android 5.0 and later, apps can continue to define their own custom permissions just as before and to request custom permissions from other apps through the <uses-permission> mechanism. However with the new requirement introduced in Android 5.0, you should carefully assess possible impacts on your app.
Here are some points to consider:
  • Does your app declare any <permission> elements in its manifest? If so, are they actually necessary to the proper function of your app or service? Or could you use a system default permission instead?
  • If you have <permission> elements in your app, do you know where they came from?
  • Do you actually intend for other apps to request your custom permissions through <uses-permission>?
  • Are you using boilerplate or example code in your app that includes <permission> elements? Are those permission elements actually necessary?
  • Do your custom permissions use names that are simple or based on common terms that other apps might share?

New installs and updates

As mentioned above, for new installs and updates of your app on devices running Android 4.4 or earlier are unaffected and there is no change in behavior. For new installs and updates on devices running Android 5.0 or later, the system prevents installation of your app if it defines a custom permission that is already defined by an existing resident app.

Existing installs with Android 5.0 system update

If your app uses custom permissions and is widely distributed and installed, there’s a chance that it will be affected when users receive update their devices to Android 5.0. After the system update is installed, the system revalidates installed apps, including a check of their custom permissions. If your app defines a custom permission that is already defined by another app that has already been validated, and your app is not signed with the same key as the other app, the systemdoes not re-install your app.

Recommendations

On devices running Android 5.0 or later, we recommend that you examine your app immediately, make any adjustments needed, and publish the updated version as soon as possible to your users.
  • If you are using custom permissions in your app, consider their origin and whether you actually need them. Remove all<permission> elements from your app, unless you are certain that they are required for proper function of your app.
  • Consider replacing your custom permissions with system default permissions where possible.
  • If your app requires custom permissions, rename your custom permissions to be unique to your app, such as by appending them to the full package name of your app.
  • If you have a suite of apps signed with different keys and the apps access a shared component by means of a custom permission, make sure that the custom permission is only defined once, in the shared component. Apps that use the shared component should not define the custom permission themselves, but should instead request access through the <uses-permission> mechanism.
  • If you have a suite of apps are signed with the same key, each app can define the same custom permission(s) asneeded — the system allows the apps to be installed in the usual way.

TLS/SSL Default Configuration Changes

Android 5.0 introduces changes the default TLS/SSL configuration used by apps for HTTPS and other TLS/SSL traffic:
  • TLSv1.2 and TLSv1.1 protocols are now enabled,
  • AES-GCM (AEAD) cipher suites are now enabled,
  • MD5, 3DES, export, and static key ECDH cipher suites are now disabled,
  • Forward Secrecy cipher suites (ECDHE and DHE) are preferred.
These changes may lead to breakages in HTTPS or TLS/SSL connectivity in a small number of cases listed below.
Note that the security ProviderInstaller from Google Play services already offers these changes across Android platform versions back to Android 2.3.

Server does not support any of the enabled ciphers suites

For example, a server might support only 3DES or MD5 cipher suites. The preferred fix is to improve the server’s configuration to enable stronger and more modern cipher suites and protocols. Ideally, TLSv1.2 and AES-GCM should be enabled, and Forward Secrecy cipher suites (ECDHE, DHE) should be enabled and preferred.
An alternative is to modify the app to use a custom SSLSocketFactory to communicate with the server. The factory should be designed to create SSLSocket instances which have some of the cipher suites required by the server enabled in addition to default cipher suites.

App is making wrong assumptions about cipher suites used to connect to server

For example, some apps contain a custom X509TrustManager that breaks because it expects the authType parameter to be RSA but encounters ECDHE_RSA or DHE_RSA.

Server is intolerant to TLSv1.1, TLSv1.2 or new TLS extensions

For example, the TLS/SSL handshake with a server is erroneously rejected or stalls. The preferred fix is to upgrade the server to comply with the TLS/SSL protocol. This will make the server successfully negotiate these newer protocols or negotiate TLSv1 or older protocols and ignore TLS extensions it does not understand. In some cases disabling TLSv1.1 and TLSv1.2 on the server may work as a stopgap measure until the server software is upgraded.
An alternative is to modify the app to use a custom SSLSocketFactory to communicate with the server. The factory should be designed to create SSLSocket instances with only those protocols enabled which are correctly supported by the server.

Support for Managed Profiles

Device administrators can add a managed profile to a device. This profile is owned by the administrator, giving the administrator control over the managed profile while leaving the user's personal profile, and its storage space, under the user's control. This change can affect the behavior of your existing app in the following ways.

Handling intents

Device administrators can restrict access to system applications from the managed profile. In this case, if an app fires an intent from the managed profile that would ordinarily be handled by that application, and there is no suitable handler for the intent on the managed profile, the intent causes an exception. For example, the device administrator can restrict apps on the managed profile from accessing the system's camera application. If your app is running on the managed profile and calls startActivityForResult() for MediaStore.ACTION_IMAGE_CAPTURE, and there is no app on the managed profile that can handle the intent, this results in an ActivityNotFoundException.
You can prevent this by checking that there is at least one handler for any intent before firing it. To check for a valid handler, call Intent.resolveActivity(). You can see an example of this being done in Take Photos Simply: Take a Photo with the Camera App.

Sharing files across profiles

Each profile has its own file storage. Since a file URI refers to a specific location in the file storage, this means that a file URI that is valid on one profile is not valid on the other one. This is not ordinarily a problem for an app, which usually just accesses the files it creates. However, if an app attaches a file to an intent, it is not safe to attach a file URI, since in some circumstances, the intent might be handled on the other profile. For example, a device administrator might specify that image capture events should be handled by the camera app on the personal profile. If the intent is fired by an app on the managed profile, the camera needs to be able to write the image to a location where the managed profile's apps can read it.
To be safe, when you need to attach a file to an intent that might cross from one profile to the other, you should create and use a content URI for the file. For more information about sharing files with content URIs, see Sharing Files. For example, the device administrator might whitelist ACTION_IMAGE_CAPTURE to be handled by the camera in the personal profile. The firing intent's EXTRA_OUTPUT should contain a content URI specifying where the photo should be stored. The camera app can write the image to the location specified by that URI, and the app that fired the intent would be able to read that file, even if the app is on the other profile.

Lockscreen widget support removed

Android 5.0 removes support for lockscreen widgets; it continues to support widgets on the home screen.

Portions of this page are reproduced from work created and shared by the Android Open Source Project and used according to terms described in theCreative Commons 2.5 Attribution License.

Original Page Direct link:
http://developer.android.com/about/versions/android-5.0-changes.html
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