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: 
I solved this issue and I posted my solution [in related issue on OpenCV github page](https://github.com/skvark/opencv-python/issues/46#issuecomment-518642701). But for your convenience, I will post it here also. 

In my case, I did almost all the solutions:

* installing using pip3 install opencv-python
* installing using apt install python-opencv
* I followed [@areche solution](https://github.com/skvark/opencv-python/issues/46#issuecomment-495694090), I end up with `kdelibs5-plugins` which was an important module for most of my desktop environments, so I give up on uninstalling it.

Finally, I found a solution for my case

* `pip uninstall opencv-python` on all instances of my python and virtual environments
* `pip3 uninstall opencv-python` on all instances of my python and virtual environments
* `sudo apt remove python-opencv`

then I downloaded the most recent opencv, in my case `opencv-4.1.1` , I build it.
for building :

`mkdir build; cd build; ccmake ..`
then I pressed pressed `c`, again pressed `c`, then pressed `g` to generate make files, then
`sudo make -j8`
after successful building, I copied `build\lib\python3\cv2.cpython.xxxxxx.so` to `usr/local/lib/python3.5/dist-packages/` and renamed it to `cv2.so`
Do the same for each virtualenv that you have. ( I'm not sure if it is logical, but it worked for me).

then everything worked fine without any error.
I know the thread is a bit old but posting for anyone else out there, I faced the same problem and it was because even after running

```
pip3 uninstall opencv-python

```

there was another version of open-cv in my system which I checked by

```
pip list

```

(I'm guessing that pip only removes the first version it finds)
So I ran this command again

```
pip3 uninstall opencv-python

```

And now simply installing opencv by

```
pip install opencv-python

```

worked for me.