Flutter 如何将附加参数传递给 Function(BuildContext) 回调

Question

我有一个带有回调 function 的 class

 class MyText {
  final String text;
  final List<String> variants;
  final int id;
  final TextStyle style;
  final void Function(BuildContext) callback; 
  final bool isWidgetSpan;
  final String Answer;

  MyText({
    this.text,
    this.variants,
    this.style,
    this.callback,
    this.isWidgetSpan,
    this.id,
    this.Answer
  });
}

我需要将final void Function(BuildContext) callback; 不仅是上下文，还有其他参数，例如 int 和 String。 如果我这样做

 final void Function(BuildContext, int , String) callback;

编译器同意了，但是参数类型'Null Function(BuildContext)' 不能分配给参数类型'void Function(BuildContext, int, String)'。

    var t = new MyText(
    isWidgetSpan: false,
    
   //Error pass callback
    callback: (context) {
      _showMyDialog(context, 100, "EXAMPLE" );
    },

    text: "${element.Name} ",
    style: TextStyle(
      color: Colors.grey,
      fontSize: 20,
    ));



Future<void> _showMyDialog(BuildContext context, int id, String text) async {
    return showDialog<void>(
      context: context,
      barrierDismissible: false,
      builder: (BuildContext context) {
        return AlertDialog(
          //title: Text(''),
          content: SingleChildScrollView(
            child: ListBody(
              children: <Widget>[
                RaisedButton(
                    color: Colors.green,
                    onPressed: () => {},
                    child: Text(
                      "A",
                      style: TextStyle(color: Colors.white),
                    )),
                RaisedButton(
                    color: Colors.indigo,
                    onPressed: () => {},
                    child: Text(
                      "B",
                      style: TextStyle(color: Colors.white),
                    )),
              ],
            ),
          ),
          actions: <Widget>[
            TextButton(
              child: Text('Cancel'),
              onPressed: () {
                Navigator.of(context).pop();
              },
            ),
          ],
        );
      },
    );
  }

Answer 1

定义您自己的 typedef 以创建您自己的回调 function 并用作我在步骤 2 中提到的 Text 中的参数的类型。

步骤1：

typedef MyDialogueCallback = void Function(
    BuildContext context, int index, String data);

第2步：

class MyText {
  final String text;
  final List<String> variants;
  final int id;
  final TextStyle style;
  final MyDialogueCallback callback;
  final bool isWidgetSpan;
  final String Answer;

  MyText({
    this.text,
    this.variants,
    this.style,
    this.callback,
    this.isWidgetSpan,
    this.id,
    this.Answer
  });
}

第 3 步：

var t = new MyText(
isWidgetSpan: false,
callback: (context, index, data) {
  _showMyDialog(context, 100, "EXAMPLE" );
},

text: "${element.Name} ",
style: TextStyle(
  color: Colors.grey,
  fontSize: 20,
));

Answer 2

您的callback不接受 integer 和字符串。

callback: (context, anInt, aString) { 
  _showMyDialog(context, 100, "EXAMPLE" );
},