今天在安装ADT的时候，提示“Cannot
complete the install because one or more required items could not be found.
Software being installed: Android Development Tools 0.9.6.v201002051504-24846 (com.android.ide.eclipse.adt.feature.group 0.9.6.v201002051504-24846)
Missing requirement: Android Development Tools 0.9.6.v201002051504-24846 (com.android.ide.eclipse.adt.feature.group 0.9.6.v201002051504-24846) requires 'org.eclipse.gef 0.0.0' but it could not be found
”仔细看了下，是说的org.eclipse.gef找不到，也就是adt安装的时候需要这个插件，但是找不到，关于这个问题在网上有不少解决方法，先提供以下方法仅供参考：
1.启动eclipse，点击window——>preferences——>install/update——>available software sites，点击Add，把如下几个网址添加过去
Eclipse EMF http://download.eclipse.org/modeling/emf/updates/releases/
Eclipse GMF http://download.eclipse.org/modeling/gmf/updates/releases
Eclipse Webtools http://download.eclipse.org/webtools/updates/
Google eclipse Pluginhttp://dl.google.com/eclipse/plugin/3.5
祝大家安装顺利！
方法二：
原来就是eclipse插件CDT（增加对C的支撑）丢失了
1. 下载地址：http://www.eclipse.org/cdt/downloads.php
我下载的是最新版本cdt-master-8.1.2.zip
2. 安装到eclipse上
步骤：Eclipse ->Help -> Install New Software -> 点击ADD添加 -> 名称填写CDT ，地址那里选择Archive，然后选择已下好的cdt-master-8.1.2.zip -> OK下一步下一步…最后重启Eclipse
如果遇到下列的问题
Cannot complete the install because one or more required items could not be found.
Software being installed: C/C++ Remote Launch 6.0.0.201109151620 (org.eclipse.cdt.launch.remote.feature.group 6.0.0.201109151620)
Missing requirement: C/C++ Remote Debug Launcher 2.3.0.201109151620 (org.eclipse.cdt.launch.remote 2.3.0.201109151620) requires ‘bundle org.eclipse.rse.ui [3.0.0,4.0.0)' but it could not be found
Cannot satisfy dependency:
From: C/C++ Remote Launch 6.0.0.201109151620 (org.eclipse.cdt.launch.remote.feature.group 6.0.0.201109151620)
To: org.eclipse.cdt.launch.remote [2.3.0.201109151620]
解决方法：
原因是缺少了org.eclipse.rse.ui，需要单独下载RSE组件，即RSE-runtime-3.3.1.zip ，
解压缩之后把features和plugins下面的文件拷贝到eclipse的对应目录下去，然后重启eclipse即可。然后再次安装CDT就可以成功完成啦