我该如何在小部件之间交换焦点？

如何解决我该如何在小部件之间交换焦点？

我正在使用Flutter开发平板电脑应用程序。我有一组按钮和一块画布。我要在按钮上执行拖动操作，超出按钮范围后，我要开始在画布上绘制符号并能够拖动它，直到释放触摸手势为止。到目前为止，我在按钮上插入了一个手势侦听器，并观察了按钮上的相对水平移动，并且负阈值表示触摸已经离开按钮的左侧，并且现在开始在画布上移动。但是手势侦听器被按钮卡住了，如何将焦点从按钮转移到画布上？下面是我的按钮代码：

import 'package:Flutter/material.dart';
import 'package:Flutter/widgets.dart';
import 'package:material_design_icons_Flutter/material_design_icons_Flutter.dart';

import './plan_display_page/plan_display_page.dart';
import './vars.dart' as vars;

// ignore: must_be_immutable
class DraggableMachineButton extends StatefulWidget {
  PlandisplayPageState pdps;

  DraggableMachineButton(
    PlandisplayPageState pdps,) {
    this.pdps = pdps;
  }

  @override
  State<StatefulWidget> createState() => _DraggableMachineButtonState();
}

class _DraggableMachineButtonState extends State<DraggableMachineButton> {
  PlandisplayPageState pdps;
  bool _buttonpressed = false;
  bool _loopActive = false;

  void _moveWhilepressed() async {
    // make sure that only one loop is active
    if (_loopActive) return;

    _loopActive = true;
    if (_buttonpressed) {
      print('DRAAGGGGG THE MACHINE');
      // do your thing
      setState(() {
        vars.machineDragging = true;
      });
      // wait a bit
      await Future.delayed(Duration(milliseconds: 100));
    }

    _loopActive = false;
  }

  @override
  void initState() {
    this.pdps = widget.pdps;
    super.initState();
  }

  //This is unnecessary
  @override
  void didUpdateWidget(DraggableMachineButton oldWidget) {
    super.didUpdateWidget(oldWidget);
  }

  @override
  Widget build(BuildContext context) {
    // return Focus(
    //   focusNode: null,return Listener(
      onPointerDown: (details) {
        _buttonpressed = true;
        _moveWhilepressed();
      },onPointerUp: (details) {
        _buttonpressed = false;
        _makeStopRequest();
      },onPointerCancel: (details) {
        print('cancel cancel cancel cancel');
      },onPointerSignal: (details) {
        print('SIGNAL ' + details.toString());
      },onPointerMove: (details) {
        // print('move move move ' + details.localPosition.toString());
        if (details.localPosition.dx < -10) {
          vars.startDraggingMachine = true;
          print('LOC ' + details.localPosition.toString());
          print('POS ' + details.position.toString());

          // globals.cct.canvasContainerTransformableStateBuilder.gt
          //     .onHorizontalDragStart(
          //         DragStartDetails(localPosition: details.localPosition));
          // print('xxxxxx');
          // globals.cct.canvasContainerTransformableStateBuilder.build(context);//
          // globals.cct.canvasContainerTransformableStateBuilder.onTapUp(details.localPosition);
          vars.novaCoord[0] = details.localPosition.dx;
          vars.novaCoord[1] = 0 - details.localPosition.dy;
          // _loopActive = false;
          // FocusScopeNode currentFocus = FocusScope.of(globals.cct.canvasContainerTransformableStateBuilder.context);
        }
      },child: Container(
        height: vars.buttonHeight * 1.4,width: vars.buttonWidth * 1.4,margin: EdgeInsets.only(
          right: vars.placeMachineTapped &&
                  (vars.distanceMeasurementStage < 0) &&
                  (!vars.isMachinePlaced())
              ? 0
              : 1200,),child: FittedBox(
          fit: BoxFit.fill,child: FlatButton.icon(
            icon: Icon(
              MdiIcons.expansionCard,color: Colors.greenAccent,size: vars.tokenIconSize,shape: RoundedRectangleBorder(),color: Color.fromARGB(255,70,104,132),splashColor: Colors.blueAccent,hoverColor: Colors.green,label: Text(
              'MACHINE',style: TextStyle(
                fontSize: 14.0,color: Colors.white,textAlign: TextAlign.center,//   ),// ),onpressed: () {
              if (!vars.crossingRefLinesExists) return;
//              vars.machinePositioned = true;
              vars.placeMachinetokenTapped = true;
            },);
  }

  _makeStopRequest() async {
    // pdps.connect();
    print('STOP DRAGGING THE MACHINE');
    vars.machineDragging = false;
    // pdps.sendMessage('stop',false);
  }
}