安装 Google Plugin for Eclipse 错误信息如下：
Cannot complete the install because one or more required items could not be found.
Software being installed: Google App Engine Tools for Android 3.2.3.v201304260926-rel-r42 (com.google.gdt.eclipse.mobile.android.feature.feature.group 3.2.3.v201304260926-rel-r42)
Missing requirement: Google App Engine Tools for Android 3.2.3.v201304260926-rel-r42 (com.google.gdt.eclipse.mobile.android.feature.feature.group 3.2.3.v201304260926-rel-r42) requires 'com.android.ide.eclipse.adt.feature.group 21.0.0' but it could not be found
解决办法，先安装ADT，再安装 Google Plugin for Eclipse