Random Musings on the R Developer Preview 3

Each time Google releases a new developer preview, I read what I can
to see if there are things that warrant more attention from
developers. I try to emphasize mainstream features that any developer
might reasonably use, along with things that may not
get quite as much attention, because they are buried in the JavaDocs.

The deeper we get into the release series for a new Android version,
the fewer ���big ticket��� changes appear. Android R is no exception. Many
of the changes are tweaks to things that debuted earlier, such as new class
and method names around data access auditing.

So, What���s New?

Besides stuff like the improved wireless ADB access
that Google pointed out in the DP3 release blog post,
I see a few other new items of interest:

We now have isExternalStorageManager() methods on Environment.
This is how we can find out if the user has granted us MANAGE_EXTERNAL_STORAGE.
The zero-parameter version tells us if we have such rights for external storage;
the one-parameter version tells us if we have such rights on whatever storage
volume contains the supplied File. This was a clear gap in the earlier developer
previews, so I am glad that this was added!

There is a new option with the keystore to require authentication per use
on designated keys, with developer-controlled authenticators (e.g., strong biometrics
or a device credential).

ContentResolver now has a notifyChange() method that takes a collection of Uri values,
presumably as an optimization.

ParcelFileDescriptor now has a wrap() method.
You also supply an OnCloseListener, which is notified when the underlying ParcelFileDescriptor
is closed. This could be useful for tracking file descriptor leaks ��� keep a roster
of those that you create and remove them from the list when they are closed.

Also, Android Police pointed out
that there is a new Settings option to ���auto-revoke permissions���. Basically,
if the user does not use your app for a while (���a few months���), Android will automatically
revoke certain permissions that the user has granted. Well-written apps should not
be harmed by this, but it is yet another wrinkle with runtime permissions added
by Android R, on top of the one-time permission option that debuted with DP1.

What Significantly Changed?

Besides the name changes in data access auditing,
we have:

android.view.inline moved to android.widget.inline and got a bit more in the way
of documentation. InlineContentView
feels like something layered atop of the SurfaceControlViewHost that I profiled
here
and here.
Still, it is unclear how this is going to get used in practice.

ApplicationExitInfo
got three new reasons of why your process died. Also, we can now register a
���process state summary��� via ActivityManager
and get that back in ApplicationExitInfo, to provide a bit more context about
what the app was doing at the time its process died. And, if we crashed (particularly
with an ANR), we can get details of what the threads were doing at the time.

What���s Gone?

Whatever FEATURE_CONTEXT_HUB was, it no longer exists.

Also, as part of revamping the ���resource loader��� system, they got rid
of DirectoryAssetLoader��� despite still referring to it in the preview
documentation.

While technically not ���gone���, a couple of WebView methods were deprecated:

setAllowFileAccessFromFileURLs()
setAllowUniversalAccessFromFileURLs()


What Now?

I will work on releasing an updated version of Elements of Android R
in the coming weeks, covering some of this and other things that are part of
earlier developer previews.