launchPicker method

@override Future<File?> launchPicker(List<IDetectable>? detectors)

Implementation

@override
Future<File?> launchPicker(List<IDetectable>? detectors) async {
  final completer = Completer();
  bool hasSelectedFile = false;

  /// End the completer and return null on selector window close
  void cancelledButtonListener(dart_html.Event e) {
    /// We want to delay this to give time for the completer to finish
    /// If it did not finish by selecting a file then we pass this check
    /// and we know the file selector was closed with selection
    Future.delayed(const Duration(milliseconds: 500)).then((value) {
      if (hasSelectedFile == false) {
        dart_html.window
            .removeEventListener('focus', cancelledButtonListener);
        completer.complete(null);
        return;
      }
    });
  }

  /// Listen to filepicker focus for cancel/close/x buttons
  dart_html.window.addEventListener('focus', cancelledButtonListener);

  try {
    /////////////////
    /* File Picker */
    /////////////////
    dart_html.InputElement picker =
        dart_html.FileUploadInputElement() as dart_html.InputElement;
    picker.multiple = false;
    picker.accept = accept;

    //////////////////////
    /* On Picker Change */
    //////////////////////
    picker.onChange.listen((e) async {
      if (picker.files!.isNotEmpty) {
        hasSelectedFile = true;

        // set file
        var blob = picker.files![0];
        String url = dart_html.Url.createObjectUrlFromBlob(blob);
        String? type = blob.type.toLowerCase();
        String? name = blob.name;
        int? size = blob.size;
        var file = File(blob, url, name, type, size);

        // process detectors
        if ((detectors != null) && (type.startsWith("image"))) {
          // read the file
          await file.read();

          // convert to raw rgba format
          if (file.bytes != null) {
            var codec = await instantiateImageCodec(file.bytes!);
            var frame = await codec.getNextFrame();

            var data  = await frame.image.toByteData(format: ImageByteFormat.rawRgba);
            if (data != null) {

              // create detectable image
              DetectableImage detectable = await DetectableImage.fromRgba(
                  data.buffer.asUint8List(),
                  frame.image.width,
                  frame.image.height);

              // detect in image
              for (var detector in detectors) {
                detector.detect(detectable, false);
              }
            }
          }
        }

        // return the file
        completer.complete(file);
      }
    });

    ///////////////////
    /* Launch Picker */
    ///////////////////
    picker.click();

    /////////////////////
    /* Wait for Result */
    /////////////////////
    return await completer.future;
  } catch (e) {
    Log().debug('Error Launching File Picker');
    return null;
  }
}