flutter - 在 float 操作按钮上的 onPressed 回调中从脚手架显示 snackbar

Question

我正在打电话

Scaffold.of(context).showSnackBar(SnackBar(
  content: Text("Snack text"),
));

在脚手架的floatingActionButton的onPressed内。

我收到此错误

I/flutter (18613): Scaffold.of() called with a context that does not contain a Scaffold.
I/flutter (18613): No Scaffold ancestor could be found starting from the context that was passed to 
....

当您在正文中调用 Scaffold.of(context) 时，它会指向一个解决方案。

https://docs.flutter.io/flutter/material/Scaffold/of.html

但是如果你在 FloatingActionButton

的 onPressed 中调用它，同样的解决方案就不起作用

Answer 1

更新:第二个解决方案比这个解决方案更好。

您应该将 floatingActionButton 小部件放在 Builder 小部件中。以下代码应该可以工作:

@override
  Widget build(BuildContext context) {
    return new Scaffold(
      floatingActionButton: new Builder(builder: (BuildContext context) {
        return new FloatingActionButton(onPressed: () {
          Scaffold
              .of(context)
              .showSnackBar(new SnackBar(content: new Text('Hello!')));
        });
      }),
      body: new Container(
        padding: new EdgeInsets.all(32.0),
        child: new Column(
          children: <Widget>[
            new MySwitch(
              value: _switchValue,
              onChanged: (bool value) {
                if (value != _switchValue) {
                  setState(() {
                    _switchValue = value;
                  });
                }
              },
            )
          ],
        ),
      ),
    );