提示：This SDK requires Developer Toolkit version 21.1.0 or above.  Current version is 21.0.1.2012-12-6-2-58.  Please update ADT to the latest version.

这样的提示是由于SDK的版本号和ADT版本不符合，会早场AVD等打不开

方案1：更新ADT

1. 在线更新（貌似最最）

在Help菜单中，选择software update…，选对available software，点击右侧的add site…，输入下载地址hhtps://dl-ssl.google.com/android/eclipse/

1. 离线更新（强烈推荐）

下载ADT  

下载之后不要解压（其实官网上已经有说明了）

直接复制过来给大家

1. Start , then select Help > Install New Software.
2. Click Add, in the top-right corner.
3. In the Add Repository dialog, click Archive.
4. Select the downloaded ADT-21.1.0.zip file and click OK.
5. Enter “ADT Plugin” for the name and click OK.
6. In the Available Software dialog, select the checkbox next to Developer Tools and click Next.
7. In the next window, you’ll see a list of the tools to be downloaded. Click Next.
8. 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.

1. When the installation completes, restart .

方案2：降低SDK

修改D:\android\IDE\sdk\tools\lib目录下的plugin.prop文件中的21.1.0更改为20.1.0

http://blog.phpfs.com/archives/1361.html