|Coding| C++ smart pointers: unique_ptr, shared_ptr, strong pointer(sp, Android)

In C++, smart pointers, unique_ptr and shared_ptr, are very common.
If you develop on Android, you may have seen strong pointer(sp), it is also a smart pointer.
Some notes about those pointers.

strong pointer in Android, can be saw as shared_ptr.
shared_ptr has a counter to record who is using this pointer in order to prevent dangerous pointer managements.