异常:尝试调用虚拟方法'int .google. android.gms.locationrequest .b()'在空对象引用上。

I have gone through some of the related topics but haven't been able to resolve my issue. Since I am at the learning phase, I am trying to implement Google's tutorial for location services. The trouble is, I am not using "LocationRequest.b()" anywhere in the code but the following error comes up when I press the Start updates button. The app subsequently crashes. Please let me know what am I doing wrong.I have gone through some of the related topics