How to save changes made to text file after opening it as a File?

Question

I have a text file in memory that I open using File.readAsString().. This extracts the text from it and saves it as a String. This is given to a TextField() so that changes can be made to this text.

How do I effectively save these changes back to the original file?

Here is my code so far. Everything works as is, the file opens and the text in it is displayed in the TextField. But I dont know how to save the changes back to file..

class _NoteEditScreenState extends State<NoteEditScreen> {

  TextEditingController _controller;

  String startingText = '';
  String fileName;


  @override
  void initState() {
    super.initState();

    getTextFromFile().whenComplete(() {
      //when we read the string, extract lines from it
      lines = lineSplitter.convert(startingText);
      setState(() {
        _controller = TextEditingController(text: startingText);
      });

    });
    fileName = widget.txtPath.split('/').last;


  }


  Future getTextFromFile() async {
    final file = File(widget.txtPath);
    //read the file
    String contents = await file.readAsString();
    startingText = contents;
  }


  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(
        appBar: AppBar(
          title: Text(fileName),
          backgroundColor: Colors.teal,
          centerTitle: true,
          actions: <Widget>[
            IconButton(
              icon: Icon(Icons.search),
              onPressed: (){
                showSearch(context: context, delegate: TextSearch(lines));
              },
            ),
          ],
        ),
        body: Center(
          child: Container(
            padding: EdgeInsets.all(5.0),
            //height: 50.0,
            child: TextField(
              maxLines: null,
              controller: _controller,
              decoration: InputDecoration(
                enabledBorder: OutlineInputBorder(
                  borderSide: BorderSide(color: Colors.teal),
                  //borderRadius: BorderRadius.all(Radius.circular(20.0))
                ),
                focusedBorder: OutlineInputBorder(
                  borderSide: BorderSide(color: Colors.red),
                  //borderRadius: BorderRadius.all(Radius.circular(20.0))
                ),
              ),
            ),
          ),
        ),

The way I see it happening is to delete the old file and create a new file with same name.. Is this the best way of doing this? Or can you guys suggest a better way?

Answer 1

To write to a file, you can use

yourFile.writeAsString(contents) or yourFile.writeAsStringSync(contents).

Use writeAsString if you don't want to wait for the file to write completely or if you don't want to block app execution, or use writeAsStringSync if you want to prevent the app from continuing until it's done writing.

Docs