title: Flutter listview with Map instead of List
body: <p>I'm trying to display the contents of my <code>HashMap</code> values in a <code>ListView.builder</code> widget. Is there a way to do this? With a <code>List</code> I could simply use the index, but how would that work with a <code>HashMap</code> without making a <code>List</code> out of it? 
  The keys of the map are strings and the values are maps with the data to display.</p>