initState method
Called when this object is inserted into the tree.
The framework will call this method exactly once for each State object it creates.
Override this method to perform initialization that depends on the location at which this object was inserted into the tree (i.e., context) or on the widget used to configure this object (i.e., widget).
If a State's build method depends on an object that can itself change state, for example a ChangeNotifier or Stream, or some other object to which one can subscribe to receive notifications, then be sure to subscribe and unsubscribe properly in initState, didUpdateWidget, and dispose:
- In initState, subscribe to the object.
- In didUpdateWidget unsubscribe from the old object and subscribe to the new one if the updated widget configuration requires replacing the object.
- In dispose, unsubscribe from the object.
You should not use BuildContext.dependOnInheritedWidgetOfExactType from this method. However, didChangeDependencies will be called immediately following this method, and BuildContext.dependOnInheritedWidgetOfExactType can be used there.
Implementations of this method should start with a call to the inherited
method, as in super.initState().
Implementation
@override
void initState() {
super.initState();
// TODO 20240613 gjw IS THIS REQUIRED?
deleteFileIfExists();
// Get the app name and version.
_loadAppInfo();
// Create the [tabController] to manage what happens on leaving/entering
// tabs.
_tabController = TabController(length: homeTabs.length, vsync: this);
// Initialize the tab widgets once in order to use IndexedStack
// later. 20250115 gjw Note that the order here must be the same as in
// [homeTabs]. There should be a better way to do this without having this
// implicit order requirement.
_tabWidgets = [
const DatasetPanel(),
const ExploreTabs(),
const TransformTabs(),
const ModelTabs(),
const EvaluatePanel(),
const RConsole(),
const ScriptTab(),
const DebugTab(),
];
// Add a listener to the TabController to perform an action when we leave
// the tab.
_tabController.addListener(() {
// Check if we are leaving the tab, not entering it.
if (!_tabController.indexIsChanging) {
// Index 0 is the DATABASE tab.
// Index 2 is the TRANSFORM tab.
if (_tabController.previousIndex == 0 ||
_tabController.previousIndex == 2) {
// 20241123 gjw For a table type dataset we want to run the
// dataset_template script.
if (ref.read(datatypeProvider) == 'table') {
// 20241008 gjw On leaving the DATASET tab we run the data template
// if there is a dataset loaded, as indicated by the path having a
// value. We need to run the template here after we have loaded and
// setup the variable roles. Trying to run the dataset template
// before leaving the DATASET tab results TARGET in and RISK being
// set to NULL.
//
// Note that variable roles are set up in
// `features/dataset/display.dart` after the dataset is loaded and
// we need to wait until the roles are set before we run the
// template.
//
// 20241123 gjw Only perform a dataset template if the path is not a
// text file.
rSource(context, ref, ['dataset_template']);
// 20241211 gjw In lib/features/dataset/display.dart we use a
// hueristic for datasets with only two columns, assuming they are
// for basket analysis. In such a case we want to set the default
// for association analysis to be Baskets. Do that here on moving
// from the DATASET tab. We do it here rather than in display.dart
// as there it creates an exception to be thrown: "Tried to modify a
// provider while the widget tree was building." It works here!
ref.read(basketsAssociationProvider.notifier).state =
ref.read(metaDataProvider).length == 2;
}
}
// You can also perform other actions here, such as showing a snackbar,
// calling a function, etc.
}
});
rSource(context, ref, ['list_package_dataset']);
}