Today me and one of my friends faced the same problem, so I have tried many things like restarting eclipse, checking updates, etc. but none was working for me.
Then I found a solution from Here and it's working as a charm for me and also for my friend.
Follow the steps here:
- Start Eclipse, then select Help > Install New Software.
- Click Add, in the top-right corner.
In the Add Repository dialog that appears, enter "ADT Plugin" for the
Name and the following URL for the Location:
https://dl-ssl.google.com/android/eclipse/
Click OK.
If you have trouble acquiring the plugin, try using "http" in the Location URL, instead of "https" (https is preferred for security reasons).
- In the Available Software dialog, select the checkbox next to
Developer Tools and click Next.
- In the next window, you'll see a list of the tools to be downloaded.
Click Next. Read and accept the license agreements, then click
Finish.
- If you get a security warning saying that the authenticity or
validity of the software can't be established, click OK.
- When the installation completes, restart Eclipse.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…