invokeCallback method

@override Future<bool> invokeCallback(Future<bool> defaultValue)

Handles a pop route request.

This method prioritizes the children list in reverse order and calls ChildBackButtonDispatcher.notifiedByParent on them. If any of them handles the request (by returning a future with true), it exits this method by returning this future. Otherwise, it keeps moving on to the next child until a child handles the request. If none of the children handles the request, this back button dispatcher will then try to handle the request by itself. This back button dispatcher handles the request by notifying the router which in turn calls the RouterDelegate.popRoute and returns its result.

To decide whether this back button dispatcher will handle the pop route request, you can override the RouterDelegate.popRoute of the router delegate you pass into the router with this back button dispatcher to return a future of true or false.

Implementation

@override
Future<bool> invokeCallback(Future<bool> defaultValue) {
  // only pop if navigator is contained in top-most route
  if (_route.isCurrent) {
    return super.invokeCallback(defaultValue);
  } else {
    parent.forget(this);
    var value = parent.invokeCallback(defaultValue);
    parent.deferTo(this);
    return value;
  }
}