转到项目中的。project文件，并在名称标签中更改项目的名称

如果项目已经从项目导航器中删除，那么右键单击项目导航器，并选择refresh以刷新工作空间。然后重新添加已删除的项目。

我也遇到过这种情况。最后，我意识到项目已经在我的工作空间中打开，但由于所选的工作集，它是不可见的。您只需取消选择活动的工作集，所有打开的项目都将变得可见。

出现此问题是因为您在其他项目文件夹中有相同的项目。因为在eclipse中我们有很多项目文件夹，所以如果你在一个文件夹中有一个项目，你想把它导入到另一个项目文件夹中，那么这个问题就会发生。 所以首先从其他文件夹中删除项目，然后导入到当前的项目文件夹中。

尝试取消选中“将项目复制到工作区”选项。

这对我很管用。

我刚接触Eclipse和Android开发，这让我困扰了很长一段时间。以下是我做错的几件事，也许将来会对别人有所帮助:

I was downloading code examples and assuming project name would be the same as the folder name and was looking for that folder name in the project explorer, not finding it, re-importing it, then getting the error message it already existed in the workspace. Yeah. Not proud of that. Didn't click on 'Copy projects into Workspace' and then searched in vain through the workspace when it didn't appear in the project explorer BECAUSE The 'Add project to working sets' option in the Import Projects tab isn't working as far as I can tell, so was not appearing in the project explorer for the active working set (refresh made no difference). Adding project to the working set had to be done after successfully importing it.