Use Picasso library to download images.
Download Link: http://repo1.maven.org/maven2/com/squareup/picasso/picasso/2.5.2/picasso-2.5.2.jar
Use android.support.v7.widget.RecyclerView instead of GridView.
Use android.support.v7.widget.CardView as single item view, due to some complecations I add the library as a package in my project.