So I'm new to godot and made a simple 3D game in Godot 4.1 and I exported it as an apk, transferred it to my phone and tested it. but when you open it it is just a black screen, and a few seconds later the app crashes. I decided to check logcat and this is the result:
USER ERROR: Error when trying to parse Variant at: parse_variant (core/io/resource_format_binary.cpp:502)
USER ERROR: Failed loading resource: res://.godot/exported/133200997/export-59a44b943e0f9c34be64df5eb51ad865-playerUI.scn. Make sure resources have been imported by opening the project in the editor at least once. at: _load (core/io/resource_loader.cpp:274)
USER ERROR: Attempt to open script 'res://.import/SpringArm.gd' resulted in error 'Can't open' at: load_source_code (modules/gdscript/gdscript.cpp:1032)
and many other errors like failed loading scene and cannot open file and can't load dependency. In my project the rendering method is forward_plus, and rendering method.mobile is mobile.
I don't know how to fix it but my guess is something to do with the rendering method as one of the errors were that it could not load a material.
I have found the answer myself. actually this game was in a project from an old version of Godot 3, after I came back to developing in Godot, I decided to work on this again, but Godot 4 has just released. so I decided to update. but every project I worked on before required me to convert it to Godot 4 because it was an older version of Godot, so some things were changed, and of course this conversion isn't fool proof and that's why I had this problem. and the solution I took to solve this, I don't like very much but I couldn't think of anything else. Basically starting a new project in Godot 4, and just copying everything I worked on from that older project. Well, it worked! it now runs on my phone without a black screen, and it doesn't crash anymore.
So the problem was converting that project from an old version of Godot to the latest and greatest Godot 4.