More info: http://androidmakers.fr/schedule/?ses… Functions that take a long time to return are a problem because they block the calling thread, which could be the main thread, where your UI runs. You can workaround this issue by using callbacks instead, but it introduces other issues: - Mangled functions signatures - Inability to use even simple language constructs like `if`, `while` or local variables - More verbose usage (boilerplate never scales well) - Harder error/exception handling …