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: 
This problem is due to the conflict between opencv-python's own Qt5 and the one used by other packages. In my case, `matplotlib` is installed via `conda`, then `pyqt` is also installed as a `matplotlib`'s dependency. My solution is as follows:

1. Uninstall `matplotlib`: `conda remove matplotlib`
2. Install `opencv-python` and `matplotlib`: `pip install matplotlib opencv-python`

Now, `matplotlib` installed via `pip` doesn't require `pyqt` and the conflict is solved.

Note: The latest version 4.5.4.x gets error with `python 3.9`, consider using lower version such as 4.5.1.x in this case.
I fixed this under Ubuntu 18.04 LTS by uninstalling any OpenCV packages from `pip` and `apt` and installing OpenCV directly from source. Maybe this tutorial will help:

<https://www.pyimagesearch.com/2018/08/15/how-to-install-opencv-4-on-ubuntu/>