how to overcome Android Studio cannot resolve symbol for android classes

You can do "File" -> "Invalidate Caches...", and select "Invalidate and Restart" option to fix this.

Android Studio suddenly cannot resolve symbols helped:

• Exit Android Studio
• Back up your project
• Delete all the .iml files and the .idea folder
• Relaunch Android Studio and reimport your project

In the menu bar

Select tools>-android>-SDK manager

and download the SDK build tools, SDK platform and Google API's( the Google API stores packages such as "import android.view.Menu" etc.) for the target SDK version of your project(20 as shown in your screenshot). if you are not sure which items you have to download , you can select all of them.(will take more time to download of course).

Restart the IDE

Delete folder: C:\Users\{your-user}\.AndroidStudio{your-version}\system\caches

It helped me