Flutter - BLoC pattern - How to use streams to invoke a method of another widget, i.e. an animation?
Suppose there is a widget with a method controlling visibility animation, toggleVisibility(). In a BLoC pattern, I want to use a stream to invoke that function. I find this pretty tricky.
- Since it is an animation rather than a complete redraw, a StreamBuilder doesn't fit.
Manually add a listener to the BLoC streams isn't convenient either.
- In
initeState()function of the target widget, we don't have a context, so it's hard to get a reference to the BLoC.
Edit: This is not the case after I read Rémi Rousselet's answer. We can access the context even outside of
build()function, becauseState<T>class has a property named 'context' and is documented in Flutter's docs.... I wasn't aware of that.
- In
build(context)function of the target widget, we have the context. But the widget can be frequently re-built, so you have to manually clean the outdated subscriptions. Otherwise it will create tons of garbages.
- In
A hack with StreamBuilder can do, since the StreamBuilder has implemented all the subscription and unsubscription functionalities. Insert a StreamBuilder somewhere in the layout of the target widget.
StreamBuilder(
stream: Bloc.of(context).stream,
builder: (context, snapshot){
toggleVisiblity();
return Container():
}
);
But this is really a hack. It mixed layout with logic and introduced a useless widget which could cause layout bugs.
So I wonder if there is a good way of doing this in flutter.
dart 
flutter rxdart asked Nov 23 '18 at 9:25
First_Strike
1128
add a comment |
Suppose there is a widget with a method controlling visibility animation, toggleVisibility(). In a BLoC pattern, I want to use a stream to invoke that function. I find this pretty tricky.
- Since it is an animation rather than a complete redraw, a StreamBuilder doesn't fit.
Manually add a listener to the BLoC streams isn't convenient either.
- In
initeState()function of the target widget, we don't have a context, so it's hard to get a reference to the BLoC.
Edit: This is not the case after I read Rémi Rousselet's answer. We can access the context even outside of
build()function, becauseState<T>class has a property named 'context' and is documented in Flutter's docs.... I wasn't aware of that.
- In
build(context)function of the target widget, we have the context. But the widget can be frequently re-built, so you have to manually clean the outdated subscriptions. Otherwise it will create tons of garbages.
- In
A hack with StreamBuilder can do, since the StreamBuilder has implemented all the subscription and unsubscription functionalities. Insert a StreamBuilder somewhere in the layout of the target widget.
StreamBuilder(
stream: Bloc.of(context).stream,
builder: (context, snapshot){
toggleVisiblity();
return Container():
}
);
But this is really a hack. It mixed layout with logic and introduced a useless widget which could cause layout bugs.
So I wonder if there is a good way of doing this in flutter.
dart flutter rxdart asked Nov 23 '18 at 9:25
First_Strike
1128
add a comment |
Suppose there is a widget with a method controlling visibility animation, toggleVisibility(). In a BLoC pattern, I want to use a stream to invoke that function. I find this pretty tricky.
- Since it is an animation rather than a complete redraw, a StreamBuilder doesn't fit.
Manually add a listener to the BLoC streams isn't convenient either.
- In
initeState()function of the target widget, we don't have a context, so it's hard to get a reference to the BLoC.
Edit: This is not the case after I read Rémi Rousselet's answer. We can access the context even outside of
build()function, becauseState<T>class has a property named 'context' and is documented in Flutter's docs.... I wasn't aware of that.
- In
build(context)function of the target widget, we have the context. But the widget can be frequently re-built, so you have to manually clean the outdated subscriptions. Otherwise it will create tons of garbages.
- In
A hack with StreamBuilder can do, since the StreamBuilder has implemented all the subscription and unsubscription functionalities. Insert a StreamBuilder somewhere in the layout of the target widget.
StreamBuilder(
stream: Bloc.of(context).stream,
builder: (context, snapshot){
toggleVisiblity();
return Container():
}
);
But this is really a hack. It mixed layout with logic and introduced a useless widget which could cause layout bugs.
So I wonder if there is a good way of doing this in flutter.
dart flutter rxdart asked Nov 23 '18 at 9:25
First_Strike
1128
Suppose there is a widget with a method controlling visibility animation, toggleVisibility(). In a BLoC pattern, I want to use a stream to invoke that function. I find this pretty tricky.
- Since it is an animation rather than a complete redraw, a StreamBuilder doesn't fit.
Manually add a listener to the BLoC streams isn't convenient either.
- In
initeState()function of the target widget, we don't have a context, so it's hard to get a reference to the BLoC.
Edit: This is not the case after I read Rémi Rousselet's answer. We can access the context even outside of
build()function, becauseState<T>class has a property named 'context' and is documented in Flutter's docs.... I wasn't aware of that.
- In
build(context)function of the target widget, we have the context. But the widget can be frequently re-built, so you have to manually clean the outdated subscriptions. Otherwise it will create tons of garbages.
- In
A hack with StreamBuilder can do, since the StreamBuilder has implemented all the subscription and unsubscription functionalities. Insert a StreamBuilder somewhere in the layout of the target widget.
StreamBuilder(
stream: Bloc.of(context).stream,
builder: (context, snapshot){
toggleVisiblity();
return Container():
}
);
But this is really a hack. It mixed layout with logic and introduced a useless widget which could cause layout bugs.
So I wonder if there is a good way of doing this in flutter.
dart flutter rxdart dart flutter rxdart asked Nov 23 '18 at 9:25
First_Strike
1128
asked Nov 23 '18 at 9:25
First_Strike
1128
edited Nov 23 '18 at 13:55
asked Nov 23 '18 at 9:25
First_Strike
1128
asked Nov 23 '18 at 9:25
First_Strike
1128
asked Nov 23 '18 at 9:25
First_Strike
1128
1128
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
You cannot use StreamBuilder to do that. You have to manually listen to the stream
class Example extends StatefulWidget {
@override
ExampleState createState() => ExampleState();
}
class ExampleState extends State<Example> {
StreamSubscription subscription;
@override
void didChangeDependencies() {
super.didChangeDependencies();
Stream stream = Bloc.of(context).foo;
subscription?.cancel();
subscription = stream.listen((value) {
// do something
});
}
@override
void dispose() {
subscription?.cancel();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Container();
}
}
answered Nov 23 '18 at 9:55
Rémi Rousselet
25k24784
Oh my. Your answer is SUPER HELPFUL. Previously I was unaware that the State<T> class has a 'context' property itself. It is only after I tried out your code and find it is actually in Flutter's source code and hidden in Flutter's docs. Thanks!
– First_Strike
Nov 23 '18 at 13:49
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "1"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53443827%2fflutter-bloc-pattern-how-to-use-streams-to-invoke-a-method-of-another-widget%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
You cannot use StreamBuilder to do that. You have to manually listen to the stream
class Example extends StatefulWidget {
@override
ExampleState createState() => ExampleState();
}
class ExampleState extends State<Example> {
StreamSubscription subscription;
@override
void didChangeDependencies() {
super.didChangeDependencies();
Stream stream = Bloc.of(context).foo;
subscription?.cancel();
subscription = stream.listen((value) {
// do something
});
}
@override
void dispose() {
subscription?.cancel();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Container();
}
}
answered Nov 23 '18 at 9:55
Rémi Rousselet
25k24784
Oh my. Your answer is SUPER HELPFUL. Previously I was unaware that the State<T> class has a 'context' property itself. It is only after I tried out your code and find it is actually in Flutter's source code and hidden in Flutter's docs. Thanks!
– First_Strike
Nov 23 '18 at 13:49
add a comment |
You cannot use StreamBuilder to do that. You have to manually listen to the stream
class Example extends StatefulWidget {
@override
ExampleState createState() => ExampleState();
}
class ExampleState extends State<Example> {
StreamSubscription subscription;
@override
void didChangeDependencies() {
super.didChangeDependencies();
Stream stream = Bloc.of(context).foo;
subscription?.cancel();
subscription = stream.listen((value) {
// do something
});
}
@override
void dispose() {
subscription?.cancel();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Container();
}
}
answered Nov 23 '18 at 9:55
Rémi Rousselet
25k24784
Oh my. Your answer is SUPER HELPFUL. Previously I was unaware that the State<T> class has a 'context' property itself. It is only after I tried out your code and find it is actually in Flutter's source code and hidden in Flutter's docs. Thanks!
– First_Strike
Nov 23 '18 at 13:49
add a comment |
You cannot use StreamBuilder to do that. You have to manually listen to the stream
class Example extends StatefulWidget {
@override
ExampleState createState() => ExampleState();
}
class ExampleState extends State<Example> {
StreamSubscription subscription;
@override
void didChangeDependencies() {
super.didChangeDependencies();
Stream stream = Bloc.of(context).foo;
subscription?.cancel();
subscription = stream.listen((value) {
// do something
});
}
@override
void dispose() {
subscription?.cancel();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Container();
}
}
answered Nov 23 '18 at 9:55
Rémi Rousselet
25k24784
You cannot use StreamBuilder to do that. You have to manually listen to the stream
class Example extends StatefulWidget {
@override
ExampleState createState() => ExampleState();
}
class ExampleState extends State<Example> {
StreamSubscription subscription;
@override
void didChangeDependencies() {
super.didChangeDependencies();
Stream stream = Bloc.of(context).foo;
subscription?.cancel();
subscription = stream.listen((value) {
// do something
});
}
@override
void dispose() {
subscription?.cancel();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Container();
}
}
answered Nov 23 '18 at 9:55
Rémi Rousselet
25k24784
answered Nov 23 '18 at 9:55
Rémi Rousselet
25k24784
answered Nov 23 '18 at 9:55
Rémi Rousselet
25k24784
answered Nov 23 '18 at 9:55
Rémi Rousselet
25k24784
25k24784
Oh my. Your answer is SUPER HELPFUL. Previously I was unaware that the State<T> class has a 'context' property itself. It is only after I tried out your code and find it is actually in Flutter's source code and hidden in Flutter's docs. Thanks!
– First_Strike
Nov 23 '18 at 13:49
add a comment |
Oh my. Your answer is SUPER HELPFUL. Previously I was unaware that the State<T> class has a 'context' property itself. It is only after I tried out your code and find it is actually in Flutter's source code and hidden in Flutter's docs. Thanks!
– First_Strike
Nov 23 '18 at 13:49
Oh my. Your answer is SUPER HELPFUL. Previously I was unaware that the State<T> class has a 'context' property itself. It is only after I tried out your code and find it is actually in Flutter's source code and hidden in Flutter's docs. Thanks!
– First_Strike
Nov 23 '18 at 13:49
Oh my. Your answer is SUPER HELPFUL. Previously I was unaware that the State<T> class has a 'context' property itself. It is only after I tried out your code and find it is actually in Flutter's source code and hidden in Flutter's docs. Thanks!
– First_Strike
Nov 23 '18 at 13:49
add a comment |
Thanks for contributing an answer to Stack Overflow!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Some of your past answers have not been well-received, and you're in danger of being blocked from answering.
Please pay close attention to the following guidance:
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53443827%2fflutter-bloc-pattern-how-to-use-streams-to-invoke-a-method-of-another-widget%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
