When going here: right-click on my project > Properties > Android the below error happens.
Thi
Eclipse seems to search the same folder for 'sdk' , so I put sdk folder back in the same folder as Eclipse's. and problem solved.
I was having the same error this morning strange as everything was fine last night.
Try cleaning all projects in workspace then restart eclipse - worked for me
Go to Help - eclipse market place - search for adt. Then update or install it. This worked for me.
Got this error after updating the Android SDK and Eclipse ADT when opening a new workspace I created just before the update (where I deleted all projects after the update.) The solution for me was to load another workspace I got containing projects and then load the new workspace again.