flutter - 未处理的异常: 'Future'类型不是 'Future'类型的子类型

Question

我试图在Dart中创建一个可重用的AlertDialog，并且能够制作一个。 UI显示出来，并且运行良好。这段代码中的唯一问题是，当我按下“保存”按钮时，它会出现以下错误:未处理的异常:类型“Future”不是类型“Future”的子类型。下面是我的AlertDialog类:

enum alertDialogAction { cancel, save }

class Dialogs {
  static Future<alertDialogAction> alertDialog(
    BuildContext context,
    String title,
    String body,
  ) {
    final action = showDialog(
        context: context,
        barrierDismissible: true,
        builder: (BuildContext context) {
          return AlertDialog(
            shape: RoundedRectangleBorder(
              borderRadius: BorderRadius.circular(10),
            ),
            title: Text(title),
            content: Text(body),
            actions: <Widget>[
              FlatButton(
                  onPressed: () =>
                      Navigator.pop(context,alertDialogAction.cancel),
                  child: Text("cancel")),
              RaisedButton(
                  color: Colors.blueAccent,
                  onPressed: () =>
                      Navigator.of(context).pop(alertDialogAction.save),
                  child: Text(
                    "save",
                    style: TextStyle(color: Colors.white),
                  )),
            ],
          );
        });
    return (action != null) ? action : alertDialogAction.cancel;
  }
 }

这是我在index.dart中的称呼:

 final action=await Dialogs.alertDialog(context,"title", "body");
 if (action == alertDialogAction.save){
      //code runs
      }

Answer 1

这是因为您在声明Future<dynamic>的同时将final action函数static的返回类型指定为alertDialog，从而返回了Future<alertDialogAction>。

为避免将来出现此类问题，请始终为您声明的所有变量指定特定类型。

Future<alertDialogAction> action = showDialog(
        context: context,
        barrierDismissible: true,
        builder: (BuildContext context) {
          return AlertDialog(
            shape: RoundedRectangleBorder(
              borderRadius: BorderRadius.circular(10),
            ),
            title: Text(title),
            content: Text(body),
            actions: <Widget>[
              FlatButton(
                  onPressed: () =>
                      Navigator.pop(context,alertDialogAction.cancel),
                  child: Text("cancel")),
              RaisedButton(
                  color: Colors.blueAccent,
                  onPressed: () =>
                      Navigator.of(context).pop(alertDialogAction.save),
                  child: Text(
                    "save",
                    style: TextStyle(color: Colors.white),
                  )),
            ],
          );
        });

并这样打电话

alertDialogAction action=await Dialogs.alertDialog(context,"title", "body");