Generally, it's considered a bad idea to make network calls directly from the Adapter. but If you are actually unable to perform your downloads in your activity/fragment prior to populating your listview, you can use one of the many libraries that do this like Volley that has a networkimageview object just for that. Or you can use the Picasso library that is build specifically for downloading images from the net and displaying in a regular imageView
Both are well documented and easy to use. (Picasso requires 1 line of code)