How to get AssetManager from a library project

I am trying to get AssetManager form a class in an Android library project, but I am getting the error:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference

This is how I call it:

public class RevPluginLoader extends AppCompatActivity {

    private List<String> copyPlugins() {
        AssetManager assetManager = getAssets();  // This is where it all fails
    }
}

How can I get the AssetManager?