Hello LexManos and Ariath,
Thanks for your replies !
@Ariath : this is a possibility, but i don't like to modify directly the FML code
@LexManos : yes, i have read the MultiMC source code, and others source codes (like Technic Launcher ...)
The problem is partially solved. I have added this line :
System.setProperty("minecraft.applet.TargetDirectory", Util.getWorkingDirectory().toString()); // getWorkingDirectory : return the folder where my launcher have downloaded files, so it's good
When i launch the launcher in Eclipse, this works very well, no error messages ... but, when i create the Runnable JAR and when I click to the "Connect" button, this error message appears :
2013-05-21 18:15:29 [sEVERE] [ForgeModLoader] Found unknown applet parent net.mi
necraft.Launcher, unable to inject!
2013-05-21 18:15:29 [iNFO] [sTDERR] Exception in thread "Thread-5" java.lang.Run
timeException: java.lang.RuntimeException
2013-05-21 18:15:29 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.FMLRelauncher
.relaunchApplet(FMLRelauncher.java:287)
2013-05-21 18:15:29 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.FMLRelauncher
.appletEntry(FMLRelauncher.java:229)
2013-05-21 18:15:29 [iNFO] [sTDERR] at net.minecraft.client.MinecraftApplet.
init(MinecraftApplet.java:25)
2013-05-21 18:15:29 [iNFO] [sTDERR] at net.minecraft.Launcher.replace(Launch
er.java:146)
2013-05-21 18:15:29 [iNFO] [sTDERR] at net.minecraft.Launcher$1.run(Launcher
.java:90)
2013-05-21 18:15:29 [iNFO] [sTDERR] Caused by: java.lang.RuntimeException
2013-05-21 18:15:29 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.FMLRelauncher
.relaunchApplet(FMLRelauncher.java:282)
2013-05-21 18:15:29 [iNFO] [sTDERR] ... 4 more
Thanks for your replies !