Cmake error: the source directory “opencv installation directory” does not appear to contain cmakelists.txt

I want to build opencv 4.5.0 in Ubuntu 20.04 this morning; In the C + + environment, I tried to learn opencv in the Linux system, but I was not familiar with the use of Linux system. I was puzzled by one step in building the environment, and the error was as follows:

Cmake error: the source directory “opencv installation directory” does not appear to contain cmakelists.txt

In Baidu search, we found many solutions provided by big men. After some attempts, we failed collectively. After carefully studying the reasons for the error and checking our opencv installation directory, we found that the specific path of our cmakelists.txt is "home"/ ××××/ Opencv/opencv master/cmakelists.txt " instead of " home/ ×××/ Opencv/cmakelists. TXT ", finally found the cause of the error and solved the problem. Therefore, I hope this article can help some beginners like me. Thank you for your support!