UPDATE:
Volley is now official and is available through the JCenter. Here’s how to import it:
implementation 'com.android.volley:volley:1.1.1'
DEPRICATED WAY:
Late to the party, but was able to import it by adding this to the build.gradle file:
dependencies {
compile 'com.mcxiaoke.volley:library:1.0.19'
}
Here is the link to unofficial Maven repo
NOTE: Volley v1.0.19 is current as of 02/05/2016. Please go to the Maven Repo (use link above), look up the latest version (line where artifactId = library) and update the version in your gradle configuration accordingly.