Passing a completed future in FutureBuilder does not produce initial snapshot with data

[Steelsmasher]

When I pass an already completed future into a FutureBuilder, the initial data isn't reflected in the snapshot until the next build cycle.

The code below waits for a future to complete before passing it to a FutureBuilder. I would expect the snapshot to have data on the first instance of the widget yet it doesn't?

main.dart

import 'package:flutter/material.dart';

main() {
    runApp(
        MaterialApp(
            home: Scaffold(
                body: Page(),
            ),
        ),
    );
}

class Page extends StatefulWidget {
    createState() => PageState();
}

class PageState extends State<Page> {

    Future<int> myFuture;
    String myText;

    initState(){
        super.initState();
        myFuture = Future.delayed(Duration(seconds: 5)).then((_){
            setState(() => myText = "I want this to display");
            return 0;
        });
    }

    build(context){
        if(myText == null){
            return Center(
                child: Text('Waiting for future to complete')
            );
        } else {
            return FutureBuilder(
                future: myFuture,
                builder: (context, snapshot) {
                    if(!snapshot.hasData) myText = "I don't want this to display";
                    return Center(
                        child: Text(myText)
                    );						
                }
            );
        }
    }
}

I'm aware of the 'initialData' parameter, but my use case means the the only data I can use only resides in the completed Future.

For now I'm using a workaround made of Stateful widgets but I would'nt think this was intended functionality of FutureBuilder?

Flutter Doctor

[√] Flutter (Channel master, v0.9.3-pre.17, on Microsoft Windows [Version 10.0.17134.285], locale en-GB)
[√] Android toolchain - develop for Android devices (Android SDK 27.0.3)
[X] Android Studio (not installed)
[√] VS Code (version 1.27.2)
[√] Connected devices (1 available)

! Doctor found issues in 1 category.

[zoechi]

I think this is an issue with your example

import 'package:flutter/material.dart';

main() {
  runApp(
    MaterialApp(
      home: Scaffold(
        body: Page(),
      ),
    ),
  );
}

class Page extends StatefulWidget {
  createState() => PageState();
}

class PageState extends State<Page> {
  Future<int> myFuture;
  String myText;

  initState() {
    super.initState();
    myFuture = Future.delayed(Duration(seconds: 3)).then((_) {
      setState(() => myText = "I want this to display");
      return 0;
    });
  }

  build(context) {
    if (myText == null) {
      return Center(child: Text('Waiting for future to complete'));
    } else {
      return FutureBuilder(
          future: myFuture,
          builder: (context, snapshot) {
            if (!snapshot.hasData) {
              myText = "I don't want this to display";
            } else {
              myText = "I want this to display ${snapshot.data}"; // added
            }

            return Center(child: Text(myText));
          });
    }
  }
}

works.
return FutureBuilder(...) is executed when setState() is called and at first if (!snapshot.hasData) { return true even when the Future was already completed and this overrides myText.
When then then if (!snapshot.hasData) { becomes false, myText is already set to "I don't want this to display" and no code is executed anymore that would set it to "I want this to display".

Closing as working as intended.

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