Question

This is the description of AppWidgetHost.startListening():

Start receiving onAppWidgetChanged
calls for your AppWidgets

I can’t find any reference to this mysterious onAppWidgetChanged thing anywhere. The only Google hits are quotes from the same piece of documentation.

What is it actually referring to? What does one need to call, override, or implement to get widget updates?

Answer 1

Its very unlikely that you need to implement a Widget host yourself. The home page is an existing Widget Host. Most likely what you are looking to do is Implement a WidgetProvider which basically means extending android.appwidget.AppWidgetProvider and overriding two methods:

onUpdate() and onReceive() some time onEnabled too. You almost never need to implement a Widget host, but if this is your goal please clarify. The widget provider is essentially a broadcast receiver which is designed to run inside widget host (usually home). The widget provider might live for only milliseconds, to process the broadcasted events and processing one of them is mandatory and must be specified in the manifest. To communicate out information the widget provider like any broadcast receiver extends context and can issue startActivity(intent) or startService(intent) I think this is most likely what you need to do unless you really are implementing a Widget Host.