I am using intellij-idea to develop android app. I created a project with an android module, but none of these :
import android.app.Activity;
import android
What you should do is,
1. Select your android project 2. press ctrl +alt + shift + S 3. Select SDK from the project settings 4. Check the files under the class path tab 5. There must be android.jar ,res ,annotations.jar Probably there should be missed one or several files in step 5. Then, 6. Go to Android SDK home path field and add your SDK folder again files even though you have all the jars and still you are getting the error ,then remove all the jars from the class path and add them again ( like in step 6). 7. Build menu -Rebuild your project.
Now your errors should disappear.