BlocListener
Learn about BlocListener and how it's used by widgets to listen to state changes.
The BlocListener
is another commonly used widget when implementing BLoCs using the flutter_bloc
library. With this widget, we can call a function whenever there’s a change in the state we monitor. The main difference between BlocListener
and BlocBuilder
is that BlocListener
doesn’t return a widget, while BlocBuilder
returns a widget that will be rebuilt every time the state changes.
Basic usage
The BlocListener
widget takes a listener()
function and an optional bloc
parameter. The listener()
function is automatically provided with a BuildContext
and a state
, and it doesn’t return anything. This listener()
function is called every time the state changes. We can use it to show a snackbar, make an API call, or perform any other action our app requires.
The widget can also be provided with a child
parameter, which will be a descendant widget of the BlocListener
widget. Note that the widget in the child
parameter will not be rebuilt when the state changes.
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