この問題を解決するには、次の 7 つの手順に従います。
1. Start Eclipse, then select Help > Install New Software.
2. Click Add, in the top-right corner.
3. 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.
4. 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.
5. 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.
6. If you get a security warning saying that the authenticity or validity of the software can't be established, click OK.
7. When the installation completes, restart Eclipse.