flutter

Question

我设法根据我拥有的数据显示了一个 RadioListTile 列表。请参阅下面的代码：

class ShipFromItemList extends StatefulWidget {
  @override
  _ShipFromItemListState createState() => _ShipFromItemListState();
}

class _ShipFromItemListState extends State<ShipFromItemList> {
  ShippingAddress _radioValue;

  @override
  Widget build(BuildContext context) {
    return ScopedModelDescendant<MainModel>(builder: (context, child, model) {
      return ListView(shrinkWrap: true, children: createRadioListUsers(model));
    });
  }

  List<Widget> createRadioListUsers(MainModel model) {
    List<Widget> widgets = [];
    for (ShippingAddress shippingAddress in model.shipaddrsList) {
      widgets.add(Column(
        children: <Widget>[
          SizedBox(height: 10),
          Container(
            child: RadioListTile(
              value: shippingAddress,
              groupValue: _radioValue,
              title: Text(
                shippingAddress?.name ?? "",
                style: Theme.of(context).textTheme.title.copyWith(fontSize: 15),
              ),
              subtitle: Text(
                shippingAddress?.address ?? "",
                style:
                    Theme.of(context).textTheme.caption.copyWith(fontSize: 13),
              ),
              secondary: Text("14.728 mi",
                  style: Theme.of(context)
                      .textTheme
                      .caption
                      .copyWith(fontSize: 13)),
              onChanged: (currentUser) {
                print("Current User ${currentUser?.name}");
                setSelectedUser(currentUser);
              },
              selected: _radioValue == shippingAddress,
              activeColor: Colors.orange,
            ),
          ),
          SizedBox(height: 10),
          Divider(
            height: 0.0,
          ),
        ],
      ));
    }
    return widgets;
  }

  setSelectedUser(ShippingAddress shippingAddress) {
    setState(() {
      _radioValue = shippingAddress;
    });
  }
}

但是，我希望有一天 returns 到 Select Radio 页面时，初始化选定的无线电是最后一个数据（我稍后会保存 firebase）。我需要什么数据保存以保持最新数据作为初始化所选收音机？

Answer 1

您应该使用此 flutter 包 https://pub.dartlang.org/packages/shared_preferences 将 _radioValue 的值存储在 sharedPrefences 中，这样您就可以在应用程序关闭并重新打开后再次调用该值。 sharedPrefences 仅存储原始值，例如 int 和 String，因此请考虑到这一点。

Answer 2

非常抱歉来不及了。

 import 'package:flutter/material.dart';

class ShowSelectRadio extends StatefulWidget {
  @override
  ShowSelectRadioState createState() {
    return new ShowSelectRadioState();
  }
}

class ShowSelectRadioState extends State<ShowSelectRadio> {
  int _currVal = 1;
  String _currText = '';

  List<GroupModel> _group = [
    GroupModel(
      text: "Flutter.dev",
      index: 1,
    ),
    GroupModel(
      text: "Inducesmile.com",
      index: 2,
    ),
    GroupModel(
      text: "Google.com",
      index: 3,
    ),
    GroupModel(
      text: "Yahoo.com",
      index: 4,
    ),
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Show Selected Radio  Example"),
      ),
      body: Column(
        children: <Widget>[
          Expanded(
            child: Center(
              child: Text(_currText,
                  style: TextStyle(
                    fontSize: 20.0,
                    fontWeight: FontWeight.bold,
                  )),
            ),
          ),
          Expanded(
              child: Container(
            height: 350.0,
            child: Column(
              children: _group
                  .map((t) => RadioListTile(
                        title: Text("${t.text}"),
                        groupValue: _currVal,
                        value: t.index,
                        onChanged: (val) {
                          setState(() {
                            _currVal = val.index;
                            _currText = t.text;
                          });
                        },
                      ))
                  .toList(),
            ),
          )),
        ],
      ),
    );
  }
}

class GroupModel {
  String text;
  int index;
  GroupModel({this.text, this.index});
}

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