// 备注下 GetView 继承StatelessWidget ，Obx继承ObxWidget继承自StatefuleWIdget ，class GetBuilder<T extends GetxController> extends StatefulWidget
abstract class GetView<T> extends StatelessWidget {
  const GetView({Key? key}) : super(key: key);

  final String? tag = null;

  T get controller => GetInstance().find<T>(tag: tag)!;

  @override
  Widget build(BuildContext context);
}

//GetxController是什么？abstract class GetxController extends DisposableInterface with ListenableMixin, ListNotifierMixin
//abstract class DisposableInterface extends GetLifeCycle  里面主要重写了onInit onReady onClose 方法

class GetBuilder<T extends GetxController> extends StatefulWidget{
 final GetControllerBuilder<T> builder;
  final Object? id;
  final String? tag;
}
class GetBuilderState<T extends GetxController> extends State<GetBuilder<T>>
    with GetStateUpdaterMixin {
  T? controller;
  bool? _isCreator = false;
  VoidCallback? _remove;
  Object? _filter;

  @override
  void initState() {
    // _GetBuilderState._currentState = this;
    super.initState();
    widget.initState?.call(this);
//判断是否已经注册
    var isRegistered = GetInstance().isRegistered<T>(tag: widget.tag);

    if (widget.global) {
      if (isRegistered) {
//判断是否已经初始化
        if (GetInstance().isPrepared<T>(tag: widget.tag)) {
          _isCreator = true;
        } else {
          _isCreator = false;
        }
//获取controller
        controller = GetInstance().find<T>(tag: widget.tag);
      } else {
//如果未注册过 就重新初始化一个controller并注册到内存中
        controller = widget.init;
        _isCreator = true;
        GetInstance().put<T>(controller!, tag: widget.tag);
      }
    } else {
      controller = widget.init;
      _isCreator = true;
      controller?.onStart();
    }
    _subscribeToController();
  }

  /// Register to listen Controller's events.
  /// It gets a reference to the remove() callback, to delete the
  /// setState "link" from the Controller.
  void _subscribeToController() {
    _remove?.call();
//addListener 是混入ListNotifierMixin里面的方法 将getUpdate 或者filterUpdate加入到_updaters数组中
    _remove = (widget.id == null)
        ? controller?.addListener(
            _filter != null ? _filterUpdate : getUpdate,
          )
        : controller?.addListenerId(
            widget.id,
            _filter != null ? _filterUpdate : getUpdate,
          );
  }

  void _filterUpdate() {
    var newFilter = widget.filter!(controller!);
    if (newFilter != _filter) {
      _filter = newFilter;
      getUpdate();
    }
  }
//这里是 mixin GetStateUpdaterMixin<T extends StatefulWidget> on State<T> { void getUpdate() {  if (mounted) setState(() {});  }}
  void getUpdate() {
    if (mounted) setState(() {});
  }
  @override
  void dispose() {
    super.dispose();
    widget.dispose?.call(this);
    if (_isCreator! || widget.assignId) {
      if (widget.autoRemove && GetInstance().isRegistered<T>(tag: widget.tag)) {
        GetInstance().delete<T>(tag: widget.tag);
      }
    }
    _remove?.call();
    controller = null;
    _isCreator = null;
    _remove = null;
    _filter = null;
  }

  @override
  Widget build(BuildContext context) {
    return widget.builder(controller!);
  }
}

mixin ListNotifierMixin on ListenableMixin {


  List<GetStateUpdate?>? _updaters = <GetStateUpdate?>[];

  HashMap<Object?, List<GetStateUpdate>>? _updatersGroupIds =
      HashMap<Object?, List<GetStateUpdate>>();

  @protected
  void refresh() {
    _notifyUpdate();
  
  }

  void _notifyUpdate() {
    for (var element in _updaters!) {
      element!();
    }
  }

  void _notifyIdUpdate(Object id) {
    if (_updatersGroupIds!.containsKey(id)) {
      final listGroup = _updatersGroupIds![id]!;
      for (var item in listGroup) {
        item();
      }
    }
  }

  @protected
  void refreshGroup(Object id) {
    _notifyIdUpdate(id);
  }



  @protected
  void notifyChildrens() {
    TaskManager.instance.notify(_updaters);
  }

  @override
  void removeListener(VoidCallback listener) {
    assert(_debugAssertNotDisposed());
    _updaters!.remove(listener);
  }

  void removeListenerId(Object id, VoidCallback listener) {
    assert(_debugAssertNotDisposed());
    if (_updatersGroupIds!.containsKey(id)) {
      _updatersGroupIds![id]!.remove(listener);
    }
    _updaters!.remove(listener);
  }

  @mustCallSuper
  void dispose() {
    assert(_debugAssertNotDisposed());
    _updaters = null;
    _updatersGroupIds = null;
  }

  @override
  Disposer addListener(GetStateUpdate listener) {

    _updaters!.add(listener);
    return () => _updaters!.remove(listener);
  }

  Disposer addListenerId(Object? key, GetStateUpdate listener) {
    _updatersGroupIds![key] ??= <GetStateUpdate>[];
    _updatersGroupIds![key]!.add(listener);
    return () => _updatersGroupIds![key]!.remove(listener);
  }
  void disposeId(Object id) {
    _updatersGroupIds!.remove(id);
  }
}

我们在调用update（）方法的时候 会执行什么

abstract class GetxController extends DisposableInterface
    with ListenableMixin, ListNotifierMixin {
  /// Rebuilds `GetBuilder` each time you call `update()`;
  /// Can take a List of [ids], that will only update the matching
  /// `GetBuilder( id: )`,
  /// [ids] can be reused among `GetBuilders` like group tags.
  /// The update will only notify the Widgets, if [condition] is true.
  void update([List<Object>? ids, bool condition = true]) {
    if (!condition) {
      return;
    }
    if (ids == null) {
      refresh();
    } else {
      for (final id in ids) {
        refreshGroup(id);
      }
    }
  }
}

总结：
GetBuilder继承statefulWidget，在initState方法里面 判断是否已经注册 （GetInstace().isRegistered(tag:widget.tag)） 如果已经注册 判断是否初始化（GetInstace().isPrepared(tag:widget.tag)）如果已经初始化就通过GetInstace().find(tag:widget.tag)获取controller,如果上面没有注册 就直接初始化并注册controller,GetInstace().put(controller!,tag:widget.tag)。
然后调用_subscribletoController(),在这里面controller.addListener(刷新方法) 或者controller.addListenerId(刷新方法) ,然后再ListNotifierMixin中将更新方法添加到updates数组中或者updatesGroupIds对象中（每个id 对应的还是_updates数组）

当我们在controller调用update或者update([''])的时候，如果传入id数组 就会遍历调用refreshGroupId（id），否则调用refresh(),
refresh调用_notifyUpdate就直接遍历_updates 调用刷新方法 执行setState({})更新
refreshGroupId 调用_notifyIdUpdate根据id，获取对应的listGroup,然后再遍历listGroup 调用刷新方法 执行setState({})更新