flutter - 无法选择列表中的第一个元素

Question

我用过这个部门。https://pub.dev/packages/flutter_reorderable_list 来创建可重新排序的列表，我做了并设置了样式。我没有使用带复选框的文本输入，而是生成了 10 个列表，其中 9 个是可点击的，但不是第一个。

class DragAndDropSubTasks extends StatefulWidget {
  DragAndDropSubTasks({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _DragAndDropSubTasksState createState() => _DragAndDropSubTasksState();
}

class ItemData {
  ItemData(this.title, this.key);

  final String title;

  // Each item in reorderable list needs stable and unique key
  final Key key;
}

enum DraggingMode {
  iOS,
  Android,
}

class _DragAndDropSubTasksState extends State<DragAndDropSubTasks> {
  List<ItemData> _items;
  _DragAndDropSubTasksState() {
    _items = List();
    for (int i = 0; i < 1; i++) {
      String label = "List item $i";
      _items.add(ItemData(label, ValueKey(i)));
    }
  }

  // Returns index of item with given key
  int _indexOfKey(Key key) {
    return _items.indexWhere((ItemData d) => d.key == key);
  }

  bool _reorderCallback(Key item, Key newPosition) {
    int draggingIndex = _indexOfKey(item);
    int newPositionIndex = _indexOfKey(newPosition);

    // Uncomment to allow only even target reorder possition
    // if (newPositionIndex % 2 == 1)
    //   return false;

    final draggedItem = _items[draggingIndex];
    setState(() {
      debugPrint("Reordering $item -> $newPosition");
      _items.removeAt(draggingIndex);
      _items.insert(newPositionIndex, draggedItem);
    });
    return true;
  }

  void _reorderDone(Key item) {
    final draggedItem = _items[_indexOfKey(item)];
    debugPrint("Reordering finished for ${draggedItem.title}}");
  }

  //
  // Reordering works by having ReorderableList widget in hierarchy
  // containing ReorderableItems widgets
  //

  DraggingMode _draggingMode = DraggingMode.iOS;

  Widget build(BuildContext context) {
    return Scaffold(
      body: ReorderableList(
        onReorder: this._reorderCallback,
        onReorderDone: this._reorderDone,
        child: CustomScrollView(
          // cacheExtent: 3000,
          slivers: <Widget>[
            SliverPadding(
              padding: EdgeInsets.only(
                  bottom: MediaQuery.of(context).padding.bottom),
              sliver: SliverList(
                delegate: SliverChildBuilderDelegate(
                  (BuildContext context, int index) {
                    return Container(
                      child: Item(
                        data: _items[index],
                        // first and last attributes affect border drawn during dragging
                        isFirst: index == 0,
                        isLast: index == _items.length - 1,
                        draggingMode: _draggingMode,
                      ),
                    );
                  },
                  childCount: _items.length,
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

class Item extends StatelessWidget {
  Item({
    this.data,
    this.isFirst,
    this.isLast,
    this.draggingMode,
  });

  final ItemData data;
  final bool isFirst;
  final bool isLast;
  final DraggingMode draggingMode;

  Widget _buildChild(BuildContext context, ReorderableItemState state) {
    var device = MediaQuery.of(context).size;

    BoxDecoration decoration;

    if (state == ReorderableItemState.dragProxy ||
        state == ReorderableItemState.dragProxyFinished) {
      // slightly transparent background white dragging (just like on iOS)
    } else {
      bool placeholder = state == ReorderableItemState.placeholder;
      decoration = BoxDecoration(
          border: Border(
              top: isFirst && !placeholder
                  ? Divider.createBorderSide(context) //
                  : BorderSide.none,
              bottom: isLast && placeholder
                  ? BorderSide.none //
                  : Divider.createBorderSide(context)),
          color: placeholder ? null : Colors.white);
    }

    // For iOS dragging mdoe, there will be drag handle on the right that triggers
    // reordering; For android mode it will be just an empty container
    Widget dragHandle = draggingMode == DraggingMode.iOS
        ? ReorderableListener(
            child: Container(
              height: device.height * 39 / 812,
              padding: EdgeInsets.only(right: 18.0, left: 18.0),
              margin: EdgeInsets.only(top: 7),
              decoration: BoxDecoration(
                borderRadius: new BorderRadius.only(
                  topRight: const Radius.circular(8.0),
                  bottomRight: const Radius.circular(8.0),
                ),
                color: Color.fromRGBO(249, 248, 255, 1),
              ),
              child: Center(child: BuildSvg('assets/svg/DragAndDropIcon.svg')),
            ),
          )
        : Container();

    Widget content = Container(
      decoration: decoration,
      child: SafeArea(
          top: false,
          bottom: false,
          child: Opacity(
            // hide content for placeholder
            opacity: state == ReorderableItemState.placeholder ? 0.0 : 1.0,
            child: IntrinsicHeight(
              child: Row(
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: <Widget>[
                  Container(
                      alignment: Alignment.centerLeft,
                      padding: EdgeInsets.only(left: 7),
                      width: device.width * 270 / 375,
                      margin: EdgeInsets.only(top: 7),
                      decoration: BoxDecoration(
                        borderRadius: new BorderRadius.only(
                          topLeft: const Radius.circular(8.0),
                          bottomLeft: const Radius.circular(8.0),
                        ),
                        color: Color.fromRGBO(249, 248, 255, 1),
                      ),
                      child: Stack(
                        children: <Widget>[
                          CheckBox('', false, Colors.white),
                          Container(
                            margin: EdgeInsets.only(left: 30),
                            child: TextFormField(
                              decoration: new InputDecoration(
                                border: InputBorder.none,
                                focusedBorder: InputBorder.none,
                              ),
                              keyboardType: TextInputType.text,
                            ),
                          ),
                        ],
                      )),
                  // Triggers the reordering
                  dragHandle,
                ],
              ),
            ),
          )),
    );

    // For android dragging mode, wrap the entire content in DelayedReorderableListener
    if (draggingMode == DraggingMode.Android) {
      content = DelayedReorderableListener(
        child: content,
      );
    }

    return content;
  }

  @override
  Widget build(BuildContext context) {
    return ReorderableItem(
      key: data.key, //
      childBuilder: _buildChild,
    );
  }
}

输入和复选框不适用于第一个列表元素，但它们确实适用于其他元素