I have this upLoadFile() void here and when I pick the file I want to display the fileName that I just picked FOR EX. "img89004.png" in the Text(fileName!)
code:

String? fileName;

void upLoadFile() async {
    final results = await FilePicker.platform.pickFiles(
      allowMultiple: false,
      type: FileType.custom,
      allowedExtensions: ['jpg', 'png'],
    );

    final path = results!.files.single.path!;
    final fileName = results.files.single.name;

    storage.uploadFile(path, fileName);

    print(fileName);
  }

//I want to display the fileName that I just picked HERE 
fileName == null
              ? const Center(child: Text('No file selected'))
              : Center(child: Text(fileName!)),

//Button
onPressed: () async {
                upLoadFile();
              },

>Solution :

This is a full example of what you need:

class FilePickerTest extends StatefulWidget {
  const FilePickerTest({Key? key}) : super(key: key);

  @override
  State<FilePickerTest> createState() => _FilePickerTestState();
}

class _FilePickerTestState extends State<FilePickerTest> {
  String _fileName = '';
  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Text(_fileName),
        InkWell(
          onTap: () {
            upLoadFile();
          },
          child: Text('Select file'),
        ),
        SizedBox(
          height: 16,
        ),
        InkWell(
          onTap: () {
            setState(() {
              _fileName = '';
            });
          },
          child: Text('Clear'),
        ),
      ],
    );
  }

  void upLoadFile() async {
    final results = await FilePicker.platform.pickFiles(
      allowMultiple: false,
      type: FileType.custom,
      allowedExtensions: ['jpg', 'png'],
    );

    if (results != null) {
      final path = results!.files.single.path!;

      _fileName = results.files.single.name;
      storage.uploadFile(path, fileName);
      setState(() {});
      print(_fileName);
    } else {
      // User canceled the picker
    }
  }
}