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Date: 2021-10-05 22:30:28 Functions: 0 0 -

          Line data    Source code
       1             : import 'package:flutter/widgets.dart';
       2             : import 'package:flutter_bloc/flutter_bloc.dart';
       3             : 
       4             : /// {@template bloc_consumer}
       5             : /// [BlocConsumer] exposes a [builder] and [listener] in order react to new
       6             : /// states.
       7             : /// [BlocConsumer] is analogous to a nested `BlocListener`
       8             : /// and `BlocBuilder` but reduces the amount of boilerplate needed.
       9             : /// [BlocConsumer] should only be used when it is necessary to both rebuild UI
      10             : /// and execute other reactions to state changes in the [bloc].
      11             : ///
      12             : /// [BlocConsumer] takes a required `BlocWidgetBuilder`
      13             : /// and `BlocWidgetListener` and an optional [bloc],
      14             : /// `BlocBuilderCondition`, and `BlocListenerCondition`.
      15             : ///
      16             : /// If the [bloc] parameter is omitted, [BlocConsumer] will automatically
      17             : /// perform a lookup using `BlocProvider` and the current `BuildContext`.
      18             : ///
      19             : /// ```dart
      20             : /// BlocConsumer<BlocA, BlocAState>(
      21             : ///   listener: (context, state) {
      22             : ///     // do stuff here based on BlocA's state
      23             : ///   },
      24             : ///   builder: (context, state) {
      25             : ///     // return widget here based on BlocA's state
      26             : ///   }
      27             : /// )
      28             : /// ```
      29             : ///
      30             : /// An optional [listenWhen] and [buildWhen] can be implemented for more
      31             : /// granular control over when [listener] and [builder] are called.
      32             : /// The [listenWhen] and [buildWhen] will be invoked on each [bloc] `state`
      33             : /// change.
      34             : /// They each take the previous `state` and current `state` and must return
      35             : /// a [bool] which determines whether or not the [builder] and/or [listener]
      36             : /// function will be invoked.
      37             : /// The previous `state` will be initialized to the `state` of the [bloc] when
      38             : /// the [BlocConsumer] is initialized.
      39             : /// [listenWhen] and [buildWhen] are optional and if they aren't implemented,
      40             : /// they will default to `true`.
      41             : ///
      42             : /// ```dart
      43             : /// BlocConsumer<BlocA, BlocAState>(
      44             : ///   listenWhen: (previous, current) {
      45             : ///     // return true/false to determine whether or not
      46             : ///     // to invoke listener with state
      47             : ///   },
      48             : ///   listener: (context, state) {
      49             : ///     // do stuff here based on BlocA's state
      50             : ///   },
      51             : ///   buildWhen: (previous, current) {
      52             : ///     // return true/false to determine whether or not
      53             : ///     // to rebuild the widget with state
      54             : ///   },
      55             : ///   builder: (context, state) {
      56             : ///     // return widget here based on BlocA's state
      57             : ///   }
      58             : /// )
      59             : /// ```
      60             : /// {@endtemplate}
      61             : class BlocConsumer<B extends BlocBase<S>, S> extends StatefulWidget {
      62             :   /// {@macro bloc_consumer}
      63           1 :   const BlocConsumer({
      64             :     Key? key,
      65             :     required this.builder,
      66             :     required this.listener,
      67             :     this.bloc,
      68             :     this.buildWhen,
      69             :     this.listenWhen,
      70           1 :   }) : super(key: key);
      71             : 
      72             :   /// The [bloc] that the [BlocConsumer] will interact with.
      73             :   /// If omitted, [BlocConsumer] will automatically perform a lookup using
      74             :   /// `BlocProvider` and the current `BuildContext`.
      75             :   final B? bloc;
      76             : 
      77             :   /// The [builder] function which will be invoked on each widget build.
      78             :   /// The [builder] takes the `BuildContext` and current `state` and
      79             :   /// must return a widget.
      80             :   /// This is analogous to the [builder] function in [StreamBuilder].
      81             :   final BlocWidgetBuilder<S> builder;
      82             : 
      83             :   /// Takes the `BuildContext` along with the [bloc] `state`
      84             :   /// and is responsible for executing in response to `state` changes.
      85             :   final BlocWidgetListener<S> listener;
      86             : 
      87             :   /// Takes the previous `state` and the current `state` and is responsible for
      88             :   /// returning a [bool] which determines whether or not to trigger
      89             :   /// [builder] with the current `state`.
      90             :   final BlocBuilderCondition<S>? buildWhen;
      91             : 
      92             :   /// Takes the previous `state` and the current `state` and is responsible for
      93             :   /// returning a [bool] which determines whether or not to call [listener] of
      94             :   /// [BlocConsumer] with the current `state`.
      95             :   final BlocListenerCondition<S>? listenWhen;
      96             : 
      97           1 :   @override
      98           1 :   State<BlocConsumer<B, S>> createState() => _BlocConsumerState<B, S>();
      99             : }
     100             : 
     101             : class _BlocConsumerState<B extends BlocBase<S>, S>
     102             :     extends State<BlocConsumer<B, S>> {
     103             :   late B _bloc;
     104             : 
     105           1 :   @override
     106             :   void initState() {
     107           1 :     super.initState();
     108           5 :     _bloc = widget.bloc ?? context.read<B>();
     109             :   }
     110             : 
     111           1 :   @override
     112             :   void didUpdateWidget(BlocConsumer<B, S> oldWidget) {
     113           1 :     super.didUpdateWidget(oldWidget);
     114           3 :     final oldBloc = oldWidget.bloc ?? context.read<B>();
     115           2 :     final currentBloc = widget.bloc ?? oldBloc;
     116           2 :     if (oldBloc != currentBloc) _bloc = currentBloc;
     117             :   }
     118             : 
     119           1 :   @override
     120             :   void didChangeDependencies() {
     121           1 :     super.didChangeDependencies();
     122           4 :     final bloc = widget.bloc ?? context.read<B>();
     123           3 :     if (_bloc != bloc) _bloc = bloc;
     124             :   }
     125             : 
     126           1 :   @override
     127             :   Widget build(BuildContext context) {
     128           3 :     if (widget.bloc == null) context.select<B, int>(identityHashCode);
     129           1 :     return BlocBuilder<B, S>(
     130           1 :       bloc: _bloc,
     131           2 :       builder: widget.builder,
     132           1 :       buildWhen: (previous, current) {
     133           2 :         if (widget.listenWhen?.call(previous, current) ?? true) {
     134           2 :           widget.listener(context, current);
     135             :         }
     136           2 :         return widget.buildWhen?.call(previous, current) ?? true;
     137             :       },
     138             :     );
     139             :   }
     140             : }

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