I faced with the same error.
The solution:
Change your proxy settings. For me I tried all the things like uninstall and system config but it did not work. When I changed the proxy settings, the list appeared in System Settings->Android SDK->SDK Platforms tab
Still you cannot select the platforms as it is not yet downloaded automatically during installation because of proxy. So just select next and it will download SDK Platforms.
Once this is done, then you can select your platforms and again say ok to download files for that platform.
Now, the last part, once the platform is downloaded successfully then in my case I also had to download NDK.
With the above steps I could successfully create an app. Happy coding!