Question: I have SDK version 25, when i import a project in android studio this error occurs. 

> 
> "Install missing platform(s) and sync project".
> 
> 
> 

If I click this link, I get another error, which says:

> 
> "The following packages are not available: - Package id
>  platforms;android-23".
> 
> 
> 

[sdk error](https://i.stack.imgur.com/hY1P2.png) 

[my SDK version](https://i.stack.imgur.com/8e89N.png)

Answer: 
The openCv author says that this problem comes from different Qt versions in openCv and the linux distro. That is: openCv comes with Qt4, but Qt5 is already installed.
This may be caused by conflicting installations of Qt libraries. The following command fixed it for me:

sudo apt-get remove libqt5x11extras5 libqt5x11extras5-dev