Reading the contents of a file into a String variable in Flutter

Question

The problem is this: I have a .txt file that contains one line of text and I need to read that line into a String variable.

Most of the methods I found return either a Future or Future and I have no idea how to convert these types into Strings. Also, I'm not sure what I'm doing wrong with readAsStringSync because I get a "FileSystemExeption: Cannot open file (OS Error: No such file or directory)", even though I have referenced it in my pubspec.yaml

class LessonPage extends StatelessWidget { LessonPage({this.title, this.appBarColor, this.barTitleColor, this.fileName});
   final String title;
   final Color appBarColor;
   final Color barTitleColor;
   final String fileName;

   @override
   Widget build(BuildContext context) {

      final file = new File(this.fileName);

      return new Scaffold(
        appBar: new AppBar(
           title: new Text(
                     this.title,
                     style: new TextStyle(color: this.barTitleColor)
                  ),
           backgroundColor: this.appBarColor,
        ),
        body: new Center(
           child: new Text(
           file.readAsStringSync(),
           softWrap: true,
        )
    ),
);

Answer 1

Embrace Futures! This use case is exactly what FutureBuilder was made for.

To read assets as strings, you don't need to construct a File. Instead, use DefaultAssetBundle to access asset files. Make sure that the asset file you want to read is declared in pubspec.yaml.

    return new Scaffold(
      appBar: new AppBar(
        title: new Text(
          this.title,
          style: new TextStyle(color: this.barTitleColor)
        ),
        backgroundColor: this.appBarColor,
      ),
      body: new Center(
        child: new FutureBuilder(
          future: DefaultAssetBundle.of(context).loadString(fileName),
          builder: (context, snapshot) {
            return new Text(snapshot.data ?? '', softWrap: true);
          }
        ),
      ),
    );

If you're reading a file that isn't an asset (for example, a file you downloaded to a temporary folder) then it's appropriate to use a File. In that case, make sure that the path is correct. Consider using FutureBuilder instead of the synchronous File APIs, for better performance.