Flutter Run method on Widget build complete

Question

I would like to be able to run functions once a Widget has finished building loading but I am unsure how   My current use case is to check if a user is authenticated and if not  redirect to a login view  I do not want to check before and push either the login view or the main view  it needs to happen after the main view has loaded  Is there anything I can use to do this

User · Answer

UPDATE  Flutter v1 8 4  Both mentioned codes are working now      Working    WidgetsBinding instance          addPostFrameCallback       gt  yourFunction context         Working   import  package flutter scheduler dart    SchedulerBinding instance addPostFrameCallback       gt  yourFunction context

User · Answer

In flutter version 1 14 6  Dart version 28   Below is what worked for me  You simply just need to bundle everything you want to happen after the build method into a separate method or function    override void initState     super initState    print  hello girl     WidgetsBinding instance      addPostFrameCallback       gt  afterLayoutWidgetBuild

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There are 3 possible ways  1  WidgetsBinding instance addPostFrameCallback       gt  yourFunc context     2  Future delayed Duration zero       gt  yourFunc context     3  Timer run      gt  yourFunc context     As for context  I needed it for use in Scaffold of context  after all my widgets were rendered  But in my humble opinion  the best way to do it is this  void main   async     WidgetsFlutterBinding ensureInitialized      all widgets are rendered here   await yourFunc      runApp  MyApp

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Best ways of doing this  1  WidgetsBinding WidgetsBinding instance addPostFrameCallback             print  quot WidgetsBinding quot             2  SchedulerBinding SchedulerBinding instance addPostFrameCallback         print  quot SchedulerBinding quot         It can be called inside initState  both will be called only once after Build widgets done with rendering   override   void initState            TODO  implement initState     super initState        print  quot initState quot        WidgetsBinding instance addPostFrameCallback             print  quot WidgetsBinding quot                SchedulerBinding instance addPostFrameCallback             print  quot SchedulerBinding quot                 both above codes will work the same as both use the similar binding framework  For the difference find the below link  https   medium com flutterworld flutter-schedulerbinding-vs-widgetsbinding-149c71cb607f

User · Answer

If you are looking for ReactNative s componentDidMount equivalent  Flutter has it  It s not that simple but it s working just the same way  In Flutter  Widgets do not handle their events directly  Instead they use their State object to do that   class MyWidget extends StatefulWidget      override   State lt StatefulWidget gt  createState     gt  MyState this      Widget build BuildContext context         build layout here    void onLoad BuildContext context         callback when layout build done    class MyState extends State lt MyWidget gt      MyWidget widget     MyState this widget       override   Widget build BuildContext context    gt  widget build context       override   void initState     gt  widget onLoad context       State initState immediately will be called once upon screen has finishes rendering the layout  And will never again be called even on hot reload if you re in debug mode  until explicitly reaches time to do so

User · Answer

If you want to do this only once  then do it because The framework will call initState   method exactly once for each State object it creates    override   void initState         super initState        WidgetsBinding instance          addPostFrameCallback       gt  executeAfterBuildComplete context         If you want to do this again and again like on back or navigate to a next screen and etc     then do it because didChangeDependencies   Called when a dependency of this State object changes  For example  if the previous call to build referenced an InheritedWidget that later changed  the framework would call this method to notify this object about the change  This method is also called immediately after initState  It is safe to call BuildContext dependOnInheritedWidgetOfExactType from this method    override   void didChangeDependencies         super didChangeDependencies        WidgetsBinding instance          addPostFrameCallback       gt  executeAfterBuildComplete context         This is the your Callback function executeAfterBuildComplete  BuildContext context        print  quot Build Process Complete quot

User · Answer

Flutter 1 2 - dart 2 2 According with the official guidelines and sources if you want to be certain that also the last frame of your layout was drawned you can write for example  import  package flutter scheduler dart    void initState        super initState       if  SchedulerBinding instance schedulerPhase    SchedulerPhase persistentCallbacks            SchedulerBinding instance addPostFrameCallback       gt  yourFunction context

User · Answer

Try SchedulerBinding    SchedulerBinding instance                  addPostFrameCallback       gt  setState                    isDataFetched   true

User · Answer

You could use   https   github com slightfoot flutter after layout  which executes a function only one time after the layout is completed  Or just look at its implementation and add it to your code  -   Which is basically    void initState         super initState        WidgetsBinding instance          addPostFrameCallback       gt  yourFunction context

[dart] Flutter: Run method on Widget build complete

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