Android Studio suddenly cannot resolve symbols

Question

Android Studio 0.4.2 was working fine and today I opened it and almost everything was red and the auto-completion had stopped working. I look at the imports and AS seems to

Answer 1

try to change your build.gradle with these value:

android { compileSdkVersion 18 buildToolsVersion '21.0.1'

defaultConfig {
    minSdkVersion 18
    targetSdkVersion 18
}