【已解决】加入头文件，却显示error: ‘’ in namespace ‘’ does not name a type

 error: ‘frame_statistics’ in namespace ‘openvslam::data’ does not name a type

解决办法：
在代码中加入#ifnedef#define#endif

#ifndef OPENVSLAM_DATA_FRAME_STATISTICS_H
#define OPENVSLAM_DATA_FRAME_STATISTICS_H
namespace openvslam{
	namespace data{
		class frame_statics{
		   ....
		   }
	 }
}
#endif