Question

我正在努力从生成的列表中删除项目。我对颤振和编程还很陌生。有人可以帮忙吗？我已经阅读了几篇文章，但我听不懂。

class AddPoll extends StatefulWidget {
      AddPoll({
        Key key,
        this.items,
        this.index,
      }): super(key: key);
      final Map items;
      final int index;
      @override
      AddPollState createState() => new AddPollState();
    }


    class AddPollState extends State < AddPoll > {

      int _index = 0;
      String q;
      Map formData = {};

      Map answers = {};
      var _items = List < Widget > ();

      _remove(keyValue) {

        print(keyValue);
        // List.from(_items)..removeAt(keyValue);
        answers.remove(keyValue);
        // answers.
      }

      void _add() {
        int keyValue = _index;
        _items = List.from(_items)..add(
          Padding(
            padding: const EdgeInsets.symmetric(horizontal: 20.0, vertical: 10),
              child: TextField(
                decoration: InputDecoration(
                  labelText: 'Answer ${keyValue+1}',
                  suffixIcon: IconButton(icon: Icon(Feather.minus_circle), onPressed: () {
                    _remove(keyValue);
                  })
                ),
                onChanged: (val) {
                  answers["a$keyValue"] = val;
                },

              ),
          ),
        );
        setState(() => ++_index);
      }

      @override
      void initState() {
        super.initState();
        _add();
      }

      save() async {

        formData = {

          'q': q,
          'a': answers
        };
        print(formData);
        Navigator.pop(context, formData);
      }

      @override
      Widget build(BuildContext context) {


        return Scaffold(

          appBar: new AppBar(
            title: Text("Add Question"),
            actions: < Widget > [
              FlatButton(
                child: Text("Save"),
                textColor: Theme.of(context).primaryColor,
                onPressed: () {
                  save();
                },
              )
            ],
          ),
          body: ListView(
            shrinkWrap: true,
            children: < Widget > [
              Padding(
                padding: const EdgeInsets.symmetric(horizontal: 20.0, vertical: 10),
                  child: TextField(
                    decoration: InputDecoration(
                      labelText: 'Question ${widget.index + 1}'

                    ),
                    onChanged: (val) => q = val,
                  ),
              ),

              ListView(
                shrinkWrap: true,
                children: _items,
              ),
              Padding(
                padding: const EdgeInsets.symmetric(horizontal: 20.0, vertical: 10.0),
                  child: FlatButton(onPressed: _add, child: Text("Add another answer"), 

              )

            ],
          ),

        );
      }
    }

Answer 1

您的删除方法应如下所示，

  _remove(keyValue) {
    setState(() {

      _items = List.from(_items)..removeAt(keyValue);
      --keyValue;
      --_index;      
    });
  }

从Flutter上动态添加的List <Widget>中删除项目

1 个答案: