Question

我正在尝试从对话框中返回布尔值，但我不明白为什么该值不会根据需要返回。我尝试过将其作为将来的值返回，并在弹出对话框后将这些值与上下文一起返回。

final bool delete = await _showDialog();
print(delete);

Future<bool> _showDialog() {
bool result;

showDialog(
  context: context,
  builder: (BuildContext context) {
    return AlertDialog(
      title: Text('Delete Appointment'),
      content: Text(
        'Are you sure? \nThis action cannot undo.',
        style: TextStyle(
          color: Colors.red,
          fontSize: 20
        ),
      ),
      actions: <Widget>[
        FlatButton(
          color: Colors.blue,
          child: Text(
            'CANCEL',
            style: TextStyle(
              color: Colors.white,
              fontSize: 20
            ),
          ),
          onPressed: () {
            setState(() => result = false);
            //print(result);
            Navigator.pop(context, result);
            return Future.value(result);
          },
        ),
        SizedBox(
          width: 50,
        ),
        FlatButton(
          color: Colors.red,
          child: Text(
            'CONFIRM',
            style: TextStyle(
              color: Colors.white,
              fontSize: 20
            ),
          ),
          onPressed: () {
            setState(() => result = true);
            //print(result);
            Navigator.pop(context, result);
            return Future.value(result);
          },
        )
      ],
    );
  }
);
}

Answer 1

这是一个基于您的代码的有效示例：

@override
Widget build(BuildContext context) {
  return Container(
    child: RaisedButton(onPressed: () async {
      bool delete = await _showDialog(context);
      print(delete);
    })
  );
}

Future<bool> _showDialog(context) {
  return showDialog(
    context: context,
    builder: (BuildContext context) {
      return AlertDialog(
        title: Text('Delete Appointment'),
        content: Text(
          'Are you sure? \nThis action cannot undo.',
          style: TextStyle(
            color: Colors.red,
            fontSize: 20
          ),
        ),
        actions: <Widget>[
          FlatButton(
            color: Colors.blue,
            child: Text(
              'CANCEL',
              style: TextStyle(
                color: Colors.white,
                fontSize: 20
              ),
            ),
            onPressed: () {
              Navigator.pop(context, false);
            },
          ),
          SizedBox(
            width: 50,
          ),
          FlatButton(
            color: Colors.red,
            child: Text(
              'CONFIRM',
              style: TextStyle(
                color: Colors.white,
                fontSize: 20
              ),
            ),
            onPressed: () {
              Navigator.pop(context, true);
            },
          )
        ],
      );
    }
  );
}

Answer 2

返回True

 Navigator.of(context).pop(true);

返回False

 Navigator.of(context).pop(false);

Answer 3

您将要返回的值传递给Navigator.pop，它将由showDialog返回：

final result = await showDialog(
  ...
  // At some point, Navigator.pop is called
  Navigator.pop(context, true);
);

print(result); // Prints: true

Answer 4

查看此完整的唤醒代码。您必须传递要返回的值。

import 'package:flutter/material.dart';

class Delete extends StatefulWidget {
  Delete({Key key}) : super(key: key);

  @override
  _DeleteState createState() => _DeleteState();
}

class _DeleteState extends State<Delete> with SingleTickerProviderStateMixin {
  int index = 0;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: RaisedButton(
          onPressed: () {
            _showDialog().then((value) {
              print(value.toString());
            });
          },
          child: Text("press ME!"),
        ),
      ),
    );
  }

  _showDialog() {
    return showDialog(
        context: context,
        builder: (BuildContext context) {
          return AlertDialog(
            title: Text('Delete Appointment'),
            content: Text(
              'Are you sure? \nThis action cannot undo.',
              style: TextStyle(color: Colors.red, fontSize: 20),
            ),
            actions: <Widget>[
              FlatButton(
                color: Colors.blue,
                child: Text(
                  'CANCEL',
                  style: TextStyle(color: Colors.white, fontSize: 20),
                ),
                onPressed: () {
                  Navigator.pop(context, false);
                },
              ),
              SizedBox(
                width: 50,
              ),
              FlatButton(
                color: Colors.red,
                child: Text(
                  'CONFIRM',
                  style: TextStyle(color: Colors.white, fontSize: 20),
                ),
                onPressed: () {
                  Navigator.pop(context, true);
                },
              )
            ],
          );
        });
  }
}

Answer 5

onPressed:() {
  result = false;
  //print(result);
  setState(() {});

  Navigator.pop(context, result);
}

或

onPressed:() {
  setState(() {
    result = false;
    //print(result);
    Navigator.pop(context, result);
  });
}

如何使用navigator.pop返回布尔值？

5 个答案: