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Date: 2021-09-21 11:48:43 Functions: 0 0 -

          Line data    Source code
       1             : import 'package:flutter/widgets.dart';
       2             : import 'package:flutter_bloc/flutter_bloc.dart';
       3             : import 'package:provider/provider.dart';
       4             : 
       5             : /// {@template bloc_consumer}
       6             : /// [BlocConsumer] exposes a [builder] and [listener] in order react to new
       7             : /// states.
       8             : /// [BlocConsumer] is analogous to a nested `BlocListener`
       9             : /// and `BlocBuilder` but reduces the amount of boilerplate needed.
      10             : /// [BlocConsumer] should only be used when it is necessary to both rebuild UI
      11             : /// and execute other reactions to state changes in the [bloc].
      12             : ///
      13             : /// [BlocConsumer] takes a required `BlocWidgetBuilder`
      14             : /// and `BlocWidgetListener` and an optional [bloc],
      15             : /// `BlocBuilderCondition`, and `BlocListenerCondition`.
      16             : ///
      17             : /// If the [bloc] parameter is omitted, [BlocConsumer] will automatically
      18             : /// perform a lookup using `BlocProvider` and the current `BuildContext`.
      19             : ///
      20             : /// ```dart
      21             : /// BlocConsumer<BlocA, BlocAState>(
      22             : ///   listener: (context, state) {
      23             : ///     // do stuff here based on BlocA's state
      24             : ///   },
      25             : ///   builder: (context, state) {
      26             : ///     // return widget here based on BlocA's state
      27             : ///   }
      28             : /// )
      29             : /// ```
      30             : ///
      31             : /// An optional [listenWhen] and [buildWhen] can be implemented for more
      32             : /// granular control over when [listener] and [builder] are called.
      33             : /// The [listenWhen] and [buildWhen] will be invoked on each [bloc] `state`
      34             : /// change.
      35             : /// They each take the previous `state` and current `state` and must return
      36             : /// a [bool] which determines whether or not the [builder] and/or [listener]
      37             : /// function will be invoked.
      38             : /// The previous `state` will be initialized to the `state` of the [bloc] when
      39             : /// the [BlocConsumer] is initialized.
      40             : /// [listenWhen] and [buildWhen] are optional and if they aren't implemented,
      41             : /// they will default to `true`.
      42             : ///
      43             : /// ```dart
      44             : /// BlocConsumer<BlocA, BlocAState>(
      45             : ///   listenWhen: (previous, current) {
      46             : ///     // return true/false to determine whether or not
      47             : ///     // to invoke listener with state
      48             : ///   },
      49             : ///   listener: (context, state) {
      50             : ///     // do stuff here based on BlocA's state
      51             : ///   },
      52             : ///   buildWhen: (previous, current) {
      53             : ///     // return true/false to determine whether or not
      54             : ///     // to rebuild the widget with state
      55             : ///   },
      56             : ///   builder: (context, state) {
      57             : ///     // return widget here based on BlocA's state
      58             : ///   }
      59             : /// )
      60             : /// ```
      61             : /// {@endtemplate}
      62             : class BlocConsumer<B extends BlocBase<S>, S> extends StatefulWidget {
      63             :   /// {@macro bloc_consumer}
      64           1 :   const BlocConsumer({
      65             :     Key? key,
      66             :     required this.builder,
      67             :     required this.listener,
      68             :     this.bloc,
      69             :     this.buildWhen,
      70             :     this.listenWhen,
      71           1 :   }) : super(key: key);
      72             : 
      73             :   /// The [bloc] that the [BlocConsumer] will interact with.
      74             :   /// If omitted, [BlocConsumer] will automatically perform a lookup using
      75             :   /// `BlocProvider` and the current `BuildContext`.
      76             :   final B? bloc;
      77             : 
      78             :   /// The [builder] function which will be invoked on each widget build.
      79             :   /// The [builder] takes the `BuildContext` and current `state` and
      80             :   /// must return a widget.
      81             :   /// This is analogous to the [builder] function in [StreamBuilder].
      82             :   final BlocWidgetBuilder<S> builder;
      83             : 
      84             :   /// Takes the `BuildContext` along with the [bloc] `state`
      85             :   /// and is responsible for executing in response to `state` changes.
      86             :   final BlocWidgetListener<S> listener;
      87             : 
      88             :   /// Takes the previous `state` and the current `state` and is responsible for
      89             :   /// returning a [bool] which determines whether or not to trigger
      90             :   /// [builder] with the current `state`.
      91             :   final BlocBuilderCondition<S>? buildWhen;
      92             : 
      93             :   /// Takes the previous `state` and the current `state` and is responsible for
      94             :   /// returning a [bool] which determines whether or not to call [listener] of
      95             :   /// [BlocConsumer] with the current `state`.
      96             :   final BlocListenerCondition<S>? listenWhen;
      97             : 
      98           1 :   @override
      99           1 :   State<BlocConsumer<B, S>> createState() => _BlocConsumerState<B, S>();
     100             : }
     101             : 
     102             : class _BlocConsumerState<B extends BlocBase<S>, S>
     103             :     extends State<BlocConsumer<B, S>> {
     104             :   late B _bloc;
     105             : 
     106           1 :   @override
     107             :   void initState() {
     108           1 :     super.initState();
     109           5 :     _bloc = widget.bloc ?? context.read<B>();
     110             :   }
     111             : 
     112           1 :   @override
     113             :   void didUpdateWidget(BlocConsumer<B, S> oldWidget) {
     114           1 :     super.didUpdateWidget(oldWidget);
     115           3 :     final oldBloc = oldWidget.bloc ?? context.read<B>();
     116           2 :     final currentBloc = widget.bloc ?? oldBloc;
     117           2 :     if (oldBloc != currentBloc) _bloc = currentBloc;
     118             :   }
     119             : 
     120           1 :   @override
     121             :   void didChangeDependencies() {
     122           1 :     super.didChangeDependencies();
     123           4 :     final bloc = widget.bloc ?? context.read<B>();
     124           3 :     if (_bloc != bloc) _bloc = bloc;
     125             :   }
     126             : 
     127           1 :   @override
     128             :   Widget build(BuildContext context) {
     129           3 :     if (widget.bloc == null) context.select<B, int>(identityHashCode);
     130           1 :     return BlocBuilder<B, S>(
     131           1 :       bloc: _bloc,
     132           2 :       builder: widget.builder,
     133           1 :       buildWhen: (previous, current) {
     134           2 :         if (widget.listenWhen?.call(previous, current) ?? true) {
     135           2 :           widget.listener(context, current);
     136             :         }
     137           2 :         return widget.buildWhen?.call(previous, current) ?? true;
     138             :       },
     139             :     );
     140             :   }
     141             : }

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