processInitialRoute method
Selects the initial page that the application should display and navigates to that page. If this initialization has already been performed, it does nothing.
The priority of what page is shown is as follows: First, if there is a plugin in the App that returns data from getInitialRouteData, that data is used to navigate. Next, if there is a link that opened this application, that link is used. If there is no link that opened the application, a link with an empty string using StandardPageFactory.new in the StandardMaterialApp.pages array is searched for and navigated to. If neither of these conditions are met, the first page in the StandardMaterialApp.pages array with StandardPageFactory.group having StandardPageWithResultFactory.defaultGroup is displayed. In the case of Web, WebPageNotFound is thrown at this point.
If no page can be found, the first page in StandardMaterialApp.pages is displayed.
Implementation
void processInitialRoute() {
assert(routerDelegate is StandardRouterDelegate);
(routerDelegate as StandardRouterDelegate).processInitialRoute();
}