Recall from the basic Screenlet creation tutorial that Interactor classes extend
BaseRemoteInteractor with the listener and event as type arguments. To support
offline mode, your Interactor class must instead extend one of the following
classes. Which one depends on whether your Interactor writes data to or reads
data from a server:
BaseCacheWriteInteractor: writes data to a server. Extend this class if your Screenlet is a write Screenlet. Click here to see this class.BaseCacheReadInteractor: reads data from a server. Extend this class if your Screenlet is a read Screenlet. Click here to see this class.
In either case, the type arguments are the same: the listener and the event.
Note, however, that the event must extend CacheEvent as described above. For
example, since Add Bookmark Screenlet is a write Screenlet, to support offline
mode its Interactor class must extend BaseCacheWriteInteractor with
AddBookmarkListener and AddBookmarkEvent as type arguments:
public class AddBookmarkInteractor extends
BaseCacheWriteInteractor<AddBookmarkListener, BookmarkEvent> {...
If your Screenlet is a write Screenlet, you must change the Interactor’s
execute method to take the event instead of var args (in read Screenlets, this
method can still take var args). You can then retrieve the data you need from
the event. For example, to support offline mode, the execute method in
AddBookmarkInteractor takes BookmarkEvent as an argument. The bookmark’s
URL, title, and folder ID are then retrieved from the event for use in the
getJSONObject method that makes the server call. The execute method finishes
by setting the resulting JSONObject to the event, and then returning the
event:
@Override
public BookmarkEvent execute(BookmarkEvent bookmarkEvent) throws Exception {
validate(bookmarkEvent.getUrl(), bookmarkEvent.getFolderId());
JSONObject jsonObject = getJSONObject(bookmarkEvent.getUrl(), bookmarkEvent.getTitle(),
bookmarkEvent.getFolderId());
bookmarkEvent.setJSONObject(jsonObject);
return bookmarkEvent;
}
If your Screenlet is a read Screenlet, then you must also implement the
getIdFromArgs method of BaseCacheReadInteractor. This method takes the var
args passed to the Interactor so you can return the argument that identifies
your entity. Note that because this method requires you to return a String,
you’ll often use String.valueOf to return non-string arguments as a string.
For example, the getIdFromArgs implementation in Comment Display Screenlet’s
CommentLoadInteractor retrieves the comment ID (a long) from the first
argument and then returns it as a String:
@Override
protected String getIdFromArgs(Object... args) {
long commentId = (long) args[0];
return String.valueOf(commentId);
}
You should also change the onSuccess method to take an instance of your event
class instead of BasicEvent. This is the only change you need to make to this
method. For example, the onSuccess method in AddBookmarkInteractor supports
offline mode by taking a BookmarkEvent instead of a BasicEvent:
@Override
public void onSuccess(BookmarkEvent event) {
getListener().onAddBookmarkSuccess();
}
Now make the same change to the onFailure method, but replace the listener’s
failure method call with a call to the error method inherited from
BaseCacheListener (see the listener section above for an explanation of this
method). For the error method’s arguments, you can retrieve the exception from
the event and define a string to use as the user action. For example, to
support offline mode the onFailure method in AddBookmarkInteractor takes a
BookmarkEvent instead of a BasicEvent. Also, the method’s error call
defines the “ADD_BOOKMARK” string to indicate that the error occurred while
trying to add a bookmark to the server:
@Override public void onFailure(BookmarkEvent event) {
getListener().error(event.getException(), "ADD_BOOKMARK");
}