Flutter 再讲ChangeNotifierProvider

class MoreWorkBean extends ChangeNotifier {

  ///
  String buttonName = "查看更多";

  void setButtonName(String _name) {
    this.buttonName = _name;
    notifyListeners();
  }

  ///
  String buttonUpdateLabel = "刷新作品";

  void setButtonUpdateLabel(String _label) {
    this.buttonUpdateLabel = _label;
    notifyListeners();
  }
}

ChangeNotifierProvider<MoreWorkBean>.value(
      value: _bean,
      child:  Row(
              children: [
                FlatButton(
                    onPressed: () {
                      _bean.setButtonUpdateLabel("刷新") ;
                    },
                    child: Consumer<MoreWorkBean>(
                      builder: (BuildContext context, MoreWorkBean value, Widget child) {
                        print('触发标签');
                        return Text(value.buttonUpdateLabel);
                      },
                    )),
                FlatButton(
                  onPressed: () {
                    OneContext().pushNamed(
                      "MoreWork",
                      arguments: {"name": "余雄英", "bean": _bean},
                    ).then((value) => print('value ${value}'));
                  }, 
                  child: Consumer<MoreWorkBean>(
                    builder: (BuildContext context, MoreWorkBean value, Widget child) {
                     print('触发名字');
                       return Text(value.buttonName);
                    },
                 ),
                )
              ],
            )

这个时候点击刷新按钮后, 会在控制台打印 ‘触发标签’ 和 ‘触发名字’ , 但其实仅仅只有刷新按钮被触发, 不需要更改名字, 这时候需要用到 Selector

关于Selector的介绍

https://pub.dev/documentation/provider/latest/provider/Selector-class.html

需要Tuple配合使用

https://pub.dev/packages/tuple/install

我们将触发名字的Consumer 更换成Selector的写法后, 点击刷新就不会更改名字了.

Selector<MoreWorkBean, Tuple2<String, String>>(selector: (context, bean) {
                    return Tuple2(bean.buttonName, bean.buttonName);
                  }, builder: (BuildContext context, value, Widget child) {
                    print('触发名字');
                    return Text(value.item1);
                  }),