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。

考虑以下IDE功能:

用gradle文件同步项目 Build ->清洁项目 Build ->重建项目 File ->使缓存失效

我的简单解决方案是:

Check that there is no error line in the dependencies of the build.gradle of the app or in all the resource files in the /res directory; where some common errors are when the attribute values are left without references when using: "@string/.." "@style/.." Make sure you are not getting an error of the type Android resource linking failed when the project is rebuilt. Open the file that contains the line with the error Cannot resolve symbol 'R' Scrolling to the last line of the class with said error line Click on a position to the right of the closing key } of the class

通过这种方式，IDE警告对话框将执行r类的导入。

GL

这些在Ubuntu 12.04上都不适用。我必须做到以下几点:

sudo apt-get install lib32stdc++6
sudo apt-get install lib32z1

在那之后，我遵循了这个线程中的其他一些建议，做了Build ->清洁项目，一切都很好。

我受够了

我可绘制资源中的一个大写字母。 导入安卓。R由Android Studio(或Eclipse)添加 xml文件错误

“我也遇到过同样的问题，解决方法是:

1) Sync Project with gradle files
2) Build -> Clean Project
3) Build -> Rebuild Project
4) File -> Invalidate caches

//imp step
5) Check your xml files properly.`

     The above answers are also the ways to fix the error but if does not work for anyone  then i have an option...

只需要关闭项目，然后重新启动它，这样它就会加载引用… 跟着截图走。