how can I sync changes I made in the build.gradle into the project structure ( e.g. that AndroidStudio is recognizing the lib I added? Kind of like the "reimport all maven projects" for maven projects - just for a pure gradle project.
I read somewhere that the "Synchronize" item on the module's context menu should update the IDE's settings based on the build.gradle file.
Ok, so in the latest version of Android Studio 0.1.3, they've added a Gradle project refresh button next to the other Android specific buttons in the toolbar. Make changes manually to the build.gradle files and settings.gradle and then click this button. It should configure and refresh your project settings based on the gradle files.
One thing that has worked for me was opening the Gradle panel on the right side of the editor (above "Maven Projects" and "Commander") and clicking the refresh button. That refreshed the module settings.
My solution for newer version of Android Studio. Tested on version 3.2.1. You can selected Refresh from the menu as showing here:
来源：https://stackoverflow.com/questions/16624056/android-studio-refresh-project-with-build-gradle-changes