Cannot complete the install because one or more required items could not be found.

1、错误描述

Cannot complete the install because one or more required items could not be found.
  Software being installed: Activiti Eclipse BPMN 2.0 Designer 5.18.0.201508100929 (org.activiti.designer.feature.feature.group 5.18.0.201508100929)
  Missing requirement: Activiti Eclipse BPMN 2.0 Designer 5.18.0.201508100929 (org.activiti.designer.feature.feature.group 5.18.0.201508100929) requires 'org.eclipse.emf.transaction 1.4.0' but it could not be found

2、错误原因

      这个插件是在线下载安装，由于网络不好，导致无法下载

3、解决办法

      将这个插件下载下来，离线安装