Flutter Tensorflowlite Object Detection

Question

I am working on an object recognition application with Flutter.

When the object is detected, it shows on the screen by covering it with container.

I want to convey the title of the detected object to the user audibly. It takes the title from the list named Results and displays it as a map.

I got it to speak the specified texts with TextToSpeech, but I don't know how to do it in real time.

List<Widget> _renderBoxes() {
      return widget.results.map((re) {
        var _x = re["rect"]["x"];
        var _w = re["rect"]["w"];
        var _y = re["rect"]["y"];
        var _h = re["rect"]["h"];
        var scaleW, scaleH, x, y, w, h;

        if (widget.screenH / widget.screenW >
            widget.previewH / widget.previewW) {
          scaleW = widget.screenH / widget.previewH * widget.previewW;
          scaleH = widget.screenH;
          var difW = (scaleW - widget.screenW) / scaleW;
          x = (_x - difW / 2) * scaleW;
          w = _w * scaleW;
          if (_x < difW / 2) w -= (difW / 2 - _x) * scaleW;
          y = _y * scaleH;
          h = _h * scaleH;
        } else {
          scaleH = widget.screenW / widget.previewW * widget.previewH;
          scaleW = widget.screenW;
          var difH = (scaleH - widget.screenH) / scaleH;
          x = _x * scaleW;
          w = _w * scaleW;
          y = (_y - difH / 2) * scaleH;
          h = _h * scaleH;
          if (_y < difH / 2) h -= (difH / 2 - _y) * scaleH;
        }

        return Positioned(
          left: math.max(0, x),
          top: math.max(0, y),
          width: w,
          height: h,
          child: Container(
            padding: const EdgeInsets.only(top: 5.0, left: 5.0),
            decoration: BoxDecoration(
              border: Border.all(
                color: Colors.amber,
                width: 1.0,
              ),
            ),
            child: Text(
              "${re["detectedClass"]} ${(re["confidenceInClass"] * 100).toStringAsFixed(0)}%",
              style: const TextStyle(
                color: Colors.amber,
                fontSize: 14.0,
                fontWeight: FontWeight.bold,
              ),
            ),
          ),
        );
      }).toList();
    }

The method I tried is into the build

 _res = Map.fromIterable(widget.results, value: (e) => e.detectedClass)
        as String;

add _res value

 @override
  void initState() {
    super.initState();
    _textToSpeech.speak(_res);
  }

I called it inside the method but it gave an error: "type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'String' in type cast" and "Each child must be laid out exactly once. "