Random Musings on the N Developer Preview 2

Each time Google releases a new developer preview, I try to
talk about the changes that Google isn���t talking about.

N Developer Preview 2 is an incremental change over N Developer
Preview 1. The
announcement blog post
does not mention all that much, spending the most screen space talking
about emoji. However, despite that, there are things that you really
should know about NDP2 compared to the previous NDP1, beyond what is
mentioned there. And, yes, beyond emoji.

Regressions��� Compared to Production Android

Google changed
the ���Behavior Changes��� page
without pointing out what
the actual changes were in NDP2 compared to NDP1. Of note:

Google admitted that the file: Uri scheme is defunct, as
we discovered the hard way in NDP1

In the same section of the docs,
Google now points out that MODE_WORLD_READABLE and MODE_WORLD_WRITEABLE,
beyond merely being deprecated, will crash with a SecurityException,
and that attempts to access COLUMN_LOCAL_FILENAME from
DownloadManager will also result in a SecurityException.

The StrictMode configuration for checking for network I/O on the
main application thread must have been focused on HTTP APIs or something.
Regardless, apparently you could open and write to a Socket
directly without triggering the dreaded NetworkOnMainThreadException.
This has been tightened up. Apps that had skated by with UI-thread
network I/O due to this hole now need to be patched.

Regresssions��� Compared to NDP1

Some symbols that you used in your NDP1 tests may have been revised
in NDP2, so be compared for some compilation errors.

For example, a number of things related to multi-window support
changed:

android:minimumSize now split into android:minimumWidth
and android:minimumHeight

inMultiWindow() and inPictureInPicture() were renamed
isInMultiWindowMode() and isInPictureInPictureMode()

Mode was also added in other related spots (e.g.,
onMultiWindowChanged() is now onMultiWindowModeChanged())

Minor Bits of Goodness

While I tend to focus on the problem areas, there are some less-known
good things that arose in NDP2.

Apparently, onSaveInstanceState() and various other methods that
involved IPC, if they resulted in a TransactionTooLargeException
(e.g., the state Bundle exceeding 1MB), would fail fairly quietly.
Now, such exceptions will be wrapped in some form of RuntimeException.
This should not result in new problems, but it may result in new
exceptions. While that may cause angst, the exception details will help
you clean up your code, since it was not working correctly previously
anyway.

Debug.startMethodTracing(), IIRC, used to write its output to the
root of external storage. Now, it will write to getExternalFilesDir()
or someplace around there. In a nutshell, you will not need
WRITE_EXTERNAL_STORAGE just to capture method traces.

PowerManager now has a SUSTAINED_PERFORMANCE_WAKE_LOCK, described
as ���used by Gaming and VR applications to ensure the device provides will
provide consistent performance over a large amount of time���. It is unclear
exactly what the behavior of this will be.

Long-time Android developers will remember that Activity used to
support onRetainNonConfigurationInstance() and
getLastNonConfigurationInstance(). These were deprecated back in API
Level 11, replaced by retained fragments. For some reason, they have
been un-deprecated (de-deprecated? dis-deprecated? anti-deprecated?!?)
in NDP2.

I reported in
the NDP1 ���random musings��� post
that Activity had a new onProvideKeyboardShortcuts() method, suggesting
a greater emphasis on physical keyboards. That was removed in NDP2, with
no obvious replacement. If it was removed because I pointed it out, I
wish to apologize to onProvideKeyboardShortcuts() and its next of kin.

There is a whole new android.os.health package, described as:

Applications running in the background are responsible for a significant amount of battery usage on a typical android device. There are several things that applications can do in order to reduce their impact��� This package provides more insight into what is going on behind the scenes when an application is running.

The API seems convoluted, at least on first glance, and it is largely
undocumented at this point. But, it appears
that we can access things like the number of times our _WAKEUP alarms
were invoked, how many times our services were started, how many ANRs
we generated, how much CPU time we have used, and so forth.

Bugs

Some of the bugs that I filed against NDP1 were fixed. Of note,
it appears that the multi-window minimal-size stuff works better
and the network security configuration is no longer sensitive to whitespace.

However, some bugs that I filed are still outstanding, such as
this RemoteInput documentation gap.
Plus, all three of my TileService bugs still seem to be outstanding:

https://code.google.com/p/android/issues/detail?id=205147
https://code.google.com/p/android/issues/detail?id=205154
https://code.google.com/p/android/issues/detail?id=205155

One bug is partially fixed, and it���s an interesting one. For many years,
the documentation has claimed that you can use a content: Uri to install an app.
This does not work on production versions of Android
and did not work on NDP1,
as there was simply no activity that could handle installing with
a content: Uri. On NDP2, the activity now exists. It doesn't work, at
least in my tests, and so once I have a fresh up-to-date sample, I will
be filing a fresh bug report to match. If you are implementing some
sort of app installer, or a self-upgrading app, having content: support
is very useful for security, which is why it was frustrating that Google
ignored this for years.

I am sure that many more things changed in NDP2 than I caught in the
past couple of hours. And most of what
I pointed out in NDP1
stil holds true.