Re: [Freedos-user] (no subject) JAR on Android

[dmccunney]

On Fri, Apr 27, 2018 at 1:22 PM, Eric Auer  wrote:
>
> Hi!
>
> Actually Android is a modified version of LINUX with
> stronger separation of the directories between apps
> and other differences.

Well, sorta.  Technically, Linux is the Linux kernel - vmlizuz on
installations here.  If it uses a Linux kernel, it's a Linux system.
My old Linksys WRT54G Wifi router used a Linux kernel, and was a Linux
system.  Because the Linux kernel was open source, the firmware built
around it was too, and a variety of replacements for the stock
firmware were available,  I ran a package called Tomato.

But Android differs strongly from desktop Linux installations.  Part
of the difference is the perceived end user.  Desktop Linux systems
are multi-user, and more than one person can be logged on and working
at a time.  Android explicitly assumes a single end user, and only on
user on the system as a time.

> App install files (APK) for
> example are vaguely similar to JAR, but with DEX
> (which you can decompile to Java) instead of CLASS
> files... Wikihow says, to use Java on Android, you
> need emulators and root or other ugly tricks...

> https://en.wikipedia.org/wiki/Java_(programming_language)#Android

The technology is improving. Intel has an open source MultiOS package
that serves as a shim to let you run Java on Android and iOS by
providing interfaces to the underlying system.

> I think it would be better to re-compile your existing
> Java source code to create APK instead of installing
> various tools to run the original JAR file directly?

Given the nature of the devices Android runs on, you are best served
to rebuild specifically for it if writing in Java.  Java is nominally
"Write Once, Run Anywhere", and compiled Java code should run on
anything with a current JRE. (I run IBM's Eclipse IDE, written in
Java, under Windows and Linux here.  I use the *same* binary on both
systems.)

But the differences between things written to run on a desktop or
laptop, and those that are intended to be used on a smartphone or
tablet are vast.  The underlying functionality might be the same, but
the UI and interaction will be dramatically different.  Your code
*can't* be "one size fits all".

> However, HTML 5 & Javascript / Ecmascript might just
> work, so maybe this time Apple is not too wrong? :-)

They are the way things are going.  To make it even more fun, current
compilers are starting to compile to JavaScript instead of machine
code, and the programs will be executed by JavaScript engines doing
JIT compilation to native code, and performance equivalent to
compiling to native code in the first place.

> Cheers, Eric
>
> PS: Flash totally deserves the hate :-p

Agreed.  I run Firefox as my browser.  Flash has been a "top crasher"
for Firefox  for as long as stats have been kept.  Mozilla implemented
a plugin_helper executable called from Firefox as a sandbox plugins
ran in, so a crashing plugin wouldn't take the browser down with it.
Flash was the main reason they did so.  Adobe is still issuing
security patches for the Flash player, but other development has
stopped.  They have a beta toolkit out to assist developers in
migrating from Flash to HTML5/CSS3/JavaScript.

I keep a current Flash player around because some sites I visit use
Flash to good intent, but I'll be delighted when it goes
away.entirely.
__
Dennis

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Re: [Freedos-user] (no subject) JAR on Android

[Eric Auer]

Hi!

Actually Android is a modified version of LINUX with
stronger separation of the directories between apps
and other differences. App install files (APK) for
example are vaguely similar to JAR, but with DEX
(which you can decompile to Java) instead of CLASS
files... Wikihow says, to use Java on Android, you
need emulators and root or other ugly tricks...

https://en.wikipedia.org/wiki/Java_(programming_language)#Android

I think it would be better to re-compile your existing
Java source code to create APK instead of installing
various tools to run the original JAR file directly?

However, HTML 5 & Javascript / Ecmascript might just
work, so maybe this time Apple is not too wrong? :-)

Cheers, Eric

PS: Flash totally deserves the hate :-p

> How can a .jar be run on Android or iOS? Android is built on some
> bastardized version of JAVA but AFAIK nobody has yet produced a fully
> functional JAVA Runtime Environment (JRE) for Android. As for iOS,
> Apple seems to hate JAVA with as much fury as they do Flash.
> 
> Apple sayeth "#%#@ Flash and JAVA. HTML 5.0 is the future!"


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