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[Proposal] Add filter to ValueListenableBuilder for controlling rebuilds #91178
Description
Use case
The builder is called every time the valueListenable value changes, therefore if the value is a list and ValueListenableBuilder is used for each single item in ListView, all the items are rebuilt even if only one element of the list changes.
ValueListenableBuilder<List<String>>(
valueListenable: listNotifier,
builder: (context, value, child) {
// Called even when a different element of the list is updated.
return ListTile(title: Text(value[index].title, ...);
},
)Proposal
ValueListenableBuilder will become more convenient with a parameter that is a function to decide if the builder should be called. In the example below, the ListTile is rebuilt only when the relevant element in listNotifier.value is updated, thanks to the filter.
ValueListenableBuilder<List<String>>(
valueListenable: listNotifier,
filter: (oldValue, newValue) => newValue[index] != oldValue[index],
builder: (context, value, child) {
return ListTile(title: Text(value[index].title, ...);
},
)This optimisation is important for the app performance.
The change can also make it easier to use ValueListenableBuilder for state management.
Activity
goderbauer commentedon Feb 23, 2022
As discussed in #91179, this isn't a god idea.
github-actions commentedon Mar 10, 2022
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