Android - 调用bindservice但无法访问该服务中的任何方法

So I've been writing an app that determines your running speed, and integrates that into a workout routine. As I was new to Android, I did everything in an Activity but I've reached a point where I want to divert the speed calculation portion, and everything involving the GPS to a service, which will be bound to whatever workout is going to need it.So I've been writing an app that determines you