In every instance in all of my classes where I reference R.id.something, the R is in red and it says "cannot resolve symbol R". Also every time there is R.layout.something it is underlined in red and says "cannot resolve method setContentView(?)". The project always builds fine. It is annoying to see this all the time. I have read many other questions on here about something similar but most involved importing projects from Eclipse. I am using what I believe to be the most recent version of Android Studio and the project was created with Android Studio and worked without any "cannot resolve R" problems. I would like to know what causes this if anyone knows.


当前回答

在我的案例中,通过将Android Studio从3.1更新到3.3解决了这个问题

要更新您的Android Studio:文件->设置->系统设置->更新,然后点击立即检查。

其他回答

首先检查是否有任何错误在任何xml布局,如果然后解决它首先。

否则,从项目中删除junit依赖项并重新构建项目。

这不是错误。 如果你有错误 关闭项目。 然后打开项目 在此之后,您可以得到一个错误

Cannot resolve symbol 'default_web_client_id'

可以通过在sting值中插入Web客户端ID来解决

//有时由于不完全同步会产生问题

//所以只要按照步骤,它会做你的工作肯定

Click on Build->Clean Project and that will perform a gradle clean

在我做“建立->清洁项目”和“同步项目与gradle”。它们都不是解。我从3.3.0 => 3.2.1(恢复为项目初始状态)下构建gradle版本,它解决了我的问题。

第一个解决方案

Rebuild your gradle or invalidate/restart your system.

第二个解决方案

delete .gradle and .idea folder from your android project. So you can solve "R" problem

并且还消除了红线错误发生的任何原因你得到。