更新到了最新版的ADT居然沒有找到ndk的目錄設置，這對於ndk開發很不方便。方法也很簡單。
到http://developer.android.com/sdk/installing/installing-adt.html#Troubleshooting
這裏下載最新的adt更新一下就行。
一下是Google的原文
If you are having trouble downloading the ADT plugin after following the steps above and you are behind a firewall (such as a corporate firewall), make sure that you have properly configured your proxy settings in Eclipse. In Eclipse, you can configure proxy information from the main Eclipse menu in Window (on Mac OS X, Eclipse) > Preferences > General >Network Connections.
If you are still unable to use Eclipse to download the ADT plugin as a remote update site, you can download the ADT zip file to your local machine and manually install it:
Download the ADT Plugin zip file (do not unpack it):
Package Size MD5 Checksum ADT-23.0.4.zip 103336810 bytes 91a43dcf686ab73dec2c08b77243492b Start Eclipse, then select Help > Install New Software.
Click Add, in the top-right corner.
In the Add Repository dialog, click Archive.
Select the downloaded ADT-23.0.4.zip file and click OK.
Enter "ADT Plugin" for the name and click OK.
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.
To update your plugin once you've installed using the zip file, you will have to follow these steps again instead of the default update instructions.