Javatrans Symbian OS notes

Chris Greenhalgh, 2006-03-29; last update 2007-05-30

Introduction

This file (may) hold information specific Javatrans targetted to Symbian OS.

Restrictions

Symbian is a real pain and makes the whole of the translated code much more unreadable than it might be in ANSI C++/Posix. In particular:

no multiple inheritance, even of pure virtual classes
non-standard exceptions

Doh.

Threading issues

If using generated code from a Symbian application be aware that a symbian application normally has only a single thread, and this thread is the only thread which can perform UI operations (because the UI libraries use thread-local storage).

Based on the approach used in Java Swing, under symbian the following additional java_lang_Thread class methods can be used to (a) determine if user code is being called from the main application thread or from another (internal) thread and to (b) hand off calls to user code from an internal thread to the main application thread via a Symbian active object scheduled by the main thread (cf. the Swing event dispatch thread). These methods are:

static JAVA_BOOLEAN java_lang_Thread::isFirstThread() - comparable to javax.swing.SwingUtilities.isEventDespatchThread(), returns true if the calling thread is the main application thread and can therefor call UI methods directly.
static void java_lang_Thread::invokeLater(JavaPtr<java_lang_Runnable> runnable) - calls the provided Runnable interface's void run() method at some later time from the main thread.
static void java_lang_Thread::invokeAndWait(JavaPtr<java_lang_Runnable> runnable) - calls the provided Runnable interface's void run() method and blocks until it completes. Note that this can result in process deadlock if the main thread is unable to finish it current acitvity(s) and return to its active scheduler. I.e. never call this method if there is a change that you are also blocking the main thread.

As an additional convenience the following non-standard java_lang_Thread constructor can be used to avoid having to defined framework-supported subclasses of java_lang_Runnable in order to define the code to be called using this mechanism:

typedef void (*NATIVE_THREAD_FN)(void* arg);
java_lang_Thread::java_lang_Thread(NATIVE_THREAD_FN fn, void *arg);

Sample code/projects

I have been developing/testing for Symbian using Symbian 8.0a series 60 FP2 SDK, and Carbide.vs with Visual Studio .NET 2003.

There are two solutions in CVS:

../symbian/equip2dll/equip2dll.sln, which includes two sub-projects:

../symbian/equip2dll/equip2dll/equip2dll.vcproj - a DLL currently set up to build the files generated by the equip2generate javatrans ant target. This is a model for wrapping translated code into a DLL for use in applications or services.
../symbian/equip2dll/equip2dllTest/equip2dllTest.vcproj - a (windows/emulator) testing harness for the above DLL.

../symbian/test/test.sln, which includees a single sub-project:

../symbian/test/test.vcproj - which is a simple symbian GUI application which I have been using to run the translated tests under symbian, passing the 'console' output to a list display. This is a model for using a DLL such as the one above to build an application based on the translated code.

Although set up to build under VC++ these include the normal Symbian project and package files, and so should importable/buildable in other IDEs/environments.

Known Issues

See Javatrans_introduction.html

Change Log

2006-03-29

This document created