How to create Java app for Android. Questions [closed]_问答_开发者

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I'd like to create Java app that should work on both Android and Windows .

I created JAR Java app on Eclipse Classic 3.7.1. It works okay on Windows with Java 6 VM (http://www.java.com). BTW, I tryed j2me app for m开发者_开发百科obile phone on Windows. It does not work. Hmm....

I 've installed Jbed 1.20 on Android Emulator. That j2me app started okay there. But my own Eclipse's jar did not run. It said that "no Midlet name" in it.

Well, it seems I should develop j2me midlets for Android. Is it right? I have installed J2ME_Runner 2.0.3.7 plugin in my Eclipse. But I can't create j2me app. I tryed the following 1) I created Java project. Then I created "File-new-others-j2me midlet". The Eclipse indicates that the following strings are invalid: import javax.microedition.midlet.MIDlet; import javax.microedition.lcdui.*;

2) Next I tryed file-new-project-J2me midlet suite. I typed project name but I can fill the next screen. There are empty "Group" and "Device". Dead end.

Questions. How to create j2me midlet in Eclipse Classic for ANdroid 2.2 or 3.0? Is it possible to run Java SE Jar files on Android?

What should I install to develop j2me midlets?

What is the better tool: Eclipse or NEtBeans?

BTW, I looked at J2ME "HelloWorld" source code. Why it is so different than Java SE source code. What? Java SE and ME source codes are not compatible?

Thanks.

I don't think there is an answer to your question. Java is not everything. You will not be able to create a GUI app that works on both Android and Java Desktop.

What you can do is to separate your application core library codes and your application GUI. The core library can be shared for both Android and Java Desktop application. However, you will need to implement GUI for Android and Java Desktop separately.

I believe J2ME is an old technology. Since most smart phone OSs have their own APIs and they perform much better than J2ME, there are less attention to this technology.

If you really want to have an application which run on any platform, you should considering making a web application. All you need is web browser but, of course, you will not be able to access system functionalities of your phone or OS.

I am not exactly sure, what you want to achieve.

Sure..there are probably J2ME emulators for both, Android and Windows, but I fail to see the point in using J2ME in either Android or Windows. Programming an App for both seems hard to me due to the different capabilities of each platform (Screen resolution, input device, ...)

Maybe there is also a misunderstanding: Android is a Mobile Device that features Java, but not in the way like some mobile devices that support JavaME. On Android mostly everything(e.g. Launcher, MailClient, Dialer, AppDrawer, ...) is built to run on the DalvikVM (The JVM on Android), not just some Games/Tools. The DalvikVM provides nearly the same featureset as a desktop JavaVM, in fact you compile your class-files with a standard JavaSE compiler. You can use the same JAR libraries with Android and PC (as long as they don't use native code). So there is no need to use J2ME.

BUT: For some tasks (e.g. UI, device access) you have to distinguish between the 2 platforms, so it'll be hard to write an complete app that runs on both. But it is possible to create a JAR library with the Algorithms(maybe even the Listeners for the UI), which can be used by both, Android and PC - so you just have to build the UI for each platform seperatly.

For some hints, check out google for some Android tutorials, there are pretty good ones out there.

As for your second question: Eclipse! I never used NetBeans, so I can't tell which one is better, but there is the ADT, a plugin for AndroidDevelopment available, which is very powerful (I dare even say non-optional, even if you can develop for Android by just using Notepad and the Console)

J2ME apps won't work on PC, J2SE apps won't work on mobile phones. MIDlets are meant to be running on mobile phones so there's no way to run them on PC without emulators.

Back in old times I was developing J2ME apps in NetBeans with Wireless Toolkit tool. If you need to make MIDlets you will get all you need with that set.

Hint: developing rich feature MIDlets which should run properly on thousands of Java phones is a pain in the arse. Keep that in mind if you really want to start developing in native J2ME.