[CoMoDev] Re: The state of Java for Palm OS
- From: "Sue Spielman" <sspielman@xxxxxxxxxxxxxxxxxxxxxx>
- To: <comodev@xxxxxxxxxxxxx>
- Date: Sat, 12 Jun 2004 15:08:56 -0600
Wow...thanks for the great recap David :)! I'm glad that you found it
helpful in getting familiar with J2ME. I've sent the slides over to the DJUG
folks so they should be posted shortly. If anyone has questions on things,
feel free to give me a shout, or start a thread on it.
BTW...the 250 million device # is just mobile devices...not including PC's.
Sue
-----Original Message-----
From: comodev-bounce@xxxxxxxxxxxxx [mailto:comodev-bounce@xxxxxxxxxxxxx] On
Behalf Of David Beers
Sent: Thursday, June 10, 2004 10:02 AM
To: comodev@xxxxxxxxxxxxx
Subject: [CoMoDev] Re: The state of Java for Palm OS
Sue made a great J2ME presentation last night. I started out taking a lot
of notes, but quickly realized that her slides where going to be a lot more
comprehensive than anything I could take down. Before long those should be
available as a download here:
http://www.denverjug.org/presentations/index.html There's a LOT of good
information in there because this was condensed from her 2-day J2ME
bootcamp. Perhaps "speeded up" as much as "condensed"! ;) S'ok, I like it
fast and furious!
A couple of factoids that I found interesting to throw out there right now:
* There are 250 milliion Java enabled devices out there today. (Devices? are
we including PCs here or just "mobile" devices?)
* By 2006 that number is expected to increase to 1 billion. (OK, now that
growth obviously can be attributed mostly to mobile devices)
J2ME is a catch-all phrase for various incarnations of Java that are broken
down first by "configurations" and then by various "profiles" that sit on
top of each configuration, but most of the action these days is in the
Mobile Information Device Profile (MIDP) which is part of the Connected
Limited Device Configuration (CLDC). When you hear MIDP, think mobile
phones and 2-way pagers and think "subset of standard Java."
There is a J2ME configuration called CDC ("Connected Device Configuration")
that is actually a full-fledged implementation of Java 2 Standard Edition,
but it's for more powerful devices with windowing systems (set-top boxes and
stuff like that device I posted a link to a couple of days ago, perhaps?).
Ostensibly, CDC with its "Foundation Profile" sitting on top is supposed to
be good for devices like the powerful PDAs and smart phones we have today,
and most likely there is a CDC/FP VM that would run fine on a PocketPC. But
as the fact that CDC covers *all* the J2SE libraries started to sink in with
me I realized why Palm finally gave up on developing the PDA profile of CDC.
The Palm OS is not a windowing OS so how would something like Java's
Advanced Windowing Toolkit work on a Palm PDA or smart phone? I suspect
that even if they had achieved it, it would have been at the cost of all the
great usability and battery life of the Palm OS, so at that point it
probably had qu
estionable value. This isn't to say Java won't become a popular
programming platform on Palm-powered devices, just that for the time being
it seems like J2ME apps for Palm will use the somewhat more limited MIDP.
IBM has been working hard to extend MIDP with optional packages to provide a
satisfying experience for folks with powerful devices running Palm OS,
Windows CE, Linux, etc. but since Sue's talk wasn't focused on Palm and
PocketPC I don't really know yet how well they have succeeded. One thing I
can say: don't expect to be able to use floats or doubles.
MIDP is evolving to try to keep up with the reality that "limited devices"
are becoming less limited all the time and that people need stuff like
secure network communications (enhanced UI and secure sockets are in MIDP
2.0) so that's probably the place where Java will remain the most
interesting to PDA/smart phone developers. At least it seems to offer some
hope of enabling us to write an app that will run on Palm, PocketPC, Linux,
Symbian (?), and that's what interests me. Just what the limitations of
that app would be, I'm still not completely clear.
An advantage of MIDP's phone-centricity is the fact that as of 2.0 it's got
"over the air" provisioning (software installation) as a built-in feature.
So if you're doing a consumer product it sounds like downloads and
installations directly to the device over wireless are easy.
One of the things Sue touched on that gave some insight into the world of
Java for a guy like me who hasn't done cross-platform development is the
dilemma posed by the UI. Think about it for a moment. You've got all these
different OSes or embedded systems running on devices with very different
screen resolutions, dimensions, and color depths. Almost inevitably there
are going to be trade-offs between portability and GUI features. MIDP
allows you to handle the trade-off by taking one of two approaches:
abstraction or discovery. Abstraction leaves a lot of the UI details (how
things look, how they are positioned, etc.) to the Application Management
System (part of the VM, I suppose?) to work out. That means it is the most
portable. It's what Sue demonstrated and I can understand why: if you're
targeting the wide consumer market you can't possibly test on hundreds of
different devices, so leaving a lot of the details to the AMS, which is
presumably fully compatible with
the device it's on makes good sense. On the other hand Sue kept talking
about "giving hints" to the AMS of what you wanted the UI to look like,
which frankly freaked me out. I'd like to learn more about the discovery
approach to the UI, even though this means finding out the device
capabilities and then handling most of the drawing and painting yourself.
I'll bet there are some classes out there that can be used to draw nice UI
objects. Maybe something like this: http://www.synclast.com/ui_api.jsp
There wasn't much time for Sue to go into a lot of details, but a couple of
things got passing mention that made MIDP sound similar to the Palm OS. One
was the fact that MIDP doesn't rely on a file system for persistent storage.
Instead it uses something called RMS, which is a device-independent
record-oriented database. (Of course, Palm OS does also use files, but only
on removable media.) The basic event-driven model was familiar in many
respects as well. Not surprisingly, you can do a lot of stuff with just a
few lines of code, whereas even the simplest "Hello World" takes dozens of
lines of code using the Palm OS C API. As for using MIDP for PocketPC or MS
Smartphone, I'd venture to say you'd have to have a great desire to support
other platforms with your code as well, since the .NET Compact Framework has
many of the advantages of Java and is quite a bit more complete than MIDP.
OK, that was more than I had time to write!
David
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