A callback that is called whenever the data received by the adapter is updated.
If the adapter does not use streaming, and receives the whole answer at once, it should call onData()
once, when the data is
received.
If the adapter uses streaming, the adapter should internally build the whole received data and fire onData()
callback with the
full update data each time. For example, if during streaming, the adapter receives following chunks: '<p>T'
, 'his is an'
, and
' example</p>'
, then it should fire onData()
with: '<p>T'
, '<p>This is an'
, and '<p>This is an example</p>'
.