The emulator runs on my phone or PC but some Gameboy programs do not work correctly. What can I do?
Most likely you have found a bug in the emulator. Please submit a bug report where you describe which program does not work correctly and how the errors manifests. It helps if you take a look at existing bug reports first to see if someone else already reported the problems you have found.
Where can I find Gameboy games to run on the emulator?
The emulator runs only very slow on my device. Why can't it be faster?
At the moment Android comes without a Just-in-time compiler (JIT) to speed up execution, like the Java Runtime Environment for PCs do it, and it also comes without Java hardware support on the device, like J2ME-based devices do. Therefore the Java code has to be interpreted in software, which is very slow in comparison to a JIT or native support for Java in hardware. Until Android gets added a JIT, Java programs will run considerably slower on Android devices than on other hardware with similarly fast CPUs. And emulators rely on speed of the device...
When activated, sound is distorted. Why is that the case?
The emulator continuously send sound data to the device's sound generater. If the emulator runs at a speed of less than 100%, this stream of data gets interrupted, resulting in the sound distortions. Unfortunately, due to a missing Just-in-time compiler (JIT) on Android devices, the emulator is not even near to running at 100% of an original Gameboy. So sound is rather an experimental feature and in most cases it makes little sense to activate it :-(.
The emulator runs very slow on my mobile device. How can I speed it up?
If smooth scaling is enabled in the emulator settings (use Edit Settings from the main menu to check and edit the settings), the you may switch of smooth scaling. This improves the performance a bit (at the cost of display readability), but please don't expect miracles.
I can't install the jar file on my mobile phone. What can I do?
First make sure that you downloaded the correct version. Most Java-enabled devices run the J2ME version, Android-based devices run the Android version. On some mobile devices the code obfuscation, which is used for the normal J2ME download version to gain a few percent more emulation speed, does not work correctly. In such cases you might want to try the download file with the "nonobf" suffix in the filename. This version is a bit slower but does not obfuscate the code and runs on more mobile devices than the standard version.
For transferring the jar file to the mobile phone, the mobile phone manufacturers often offer special software, like the Nokia Application Installer, that do the job of transferring new Java applications to the phone. Take a look at your mobile devices installation manual for information on how to transfer Java applications to your phone. Sometimes it is necessary to have a .jad file that accompanies the .jar file. You can download this .jad file from the Download Page of the project.
I have downloaded the J2ME emulator but it does not work on my mobile device. Why can't I run the emulator?
The emulator does not run on every mobile device. The device must support the MIDP 2.0 profile. Additionally you should have look at the system requirements listed on the online help page for your emulator version. The forum page Supported Mobile Devices lists devices where the emulator runs.
Some mobile devices also have problems with the code obfuscation used for the standard downloaded. You may try the emulator version with the "nonobf" suffix which does not used obfuscation. It runs a bit slower but may run in cases where the obfuscated version does not work.
Sound does not work on my device, even if I try to active it. Why is that the case?
Sound support via MIDI requires the Java Media API (JSR-135) to be available on the device. If your device does not support this API, then the emulator tries to create very short sound files on-the-fly and send these to the device's sound generator. Unfortunately though, this eats a lot of resources on a device and does usually not work at all or only for a very limited time. Therefore sound will normally only work on devices supporting JSR-135 and then only if MIDI sound generation is fully supported.
The emulator starts on my device, but for some games I get an error when loading and can't start the game?
The reason is in most cases that your devices does not offer enough memory to Java applications. The emulator uses about 1 MB of Java memory plus it needs more memory to load the complete Gameboy ROM. So if your phone has e.g. only 1.5 MB of RAM free for Java applications, as e.g. the Nokia Series 40 mobile phones do, there is only enough space for ROM file that are smaller (or up) to 512 KB.