Flutter：如何禁用基于 FlatButton 的 mysql 数据库

Question

如何根据数据库中包含的值禁用FlatButton？ 我的应用程序显示从具有 4 个答案选项的数据库中提取的 5 个问题。 我的计划是在用户选择答案后禁用该按钮。 怎么处理？

我的功能

_disableButton(BuildContext context, int idSoal, String idUser) async {
    final response = await http.post(BaseUrl.cekJawaban, body: {
      'id_user': idUser,
      'id_soal': "$idSoal",
    });
    final data = jsonDecode(response.body);
    int value = data['value'];
    String pesan = data['message'];
    if (value == 1) {
      print(pesan);
    } else {
      print(pesan);
    }
  }

Mysql 接口

<?php

require "../config/connect.php";

if($_SERVER['REQUEST_METHOD']=="POST"){
    $response = array();
    $id_user = $_POST['id_user'];
    $id_soal = $_POST['id_soal'];

    $cek = "SELECT * FROM t_jawab WHERE selesai_jawab ='1' AND id_user='$id_user' AND id_soal='$id_soal'";  

    $result = mysqli_fetch_array(mysqli_query($conn, $cek));
    if (isset($result)){
        $response['value']=1;
        $response['message']="Question and answer found!";
        echo json_encode($response);
        mysqli_close($conn);
    }else{
        $response['value']=0;
        $response['message']="Question and answer not found!";
        echo json_encode($response);
    }
}

?>

Here's my table, id_soal and id_user are foreign key. If data not exist, then button active else button disabled

Answer 1

禁用按钮的一种方法是在 onPressed 函数上使用 bool 值，如下所示

`RaisedButton(
  child: Text("PRESS BUTTON"),
  onPressed: booleanCondition
    ? () => myTapCallback()
    : null
)`

如果您想显示/使用多个答案问题，您可以使用Radio<T> class

用于在多个互斥值之间进行选择。当组中的一个单选按钮被选中时，组中的其他单选按钮将不再被选中。枚举通常用于此目的。

example

    // Flutter code sample for Radio

// Here is an example of Radio widgets wrapped in ListTiles, which is similar
// to what you could get with the RadioListTile widget.
//
// The currently selected character is passed into `groupValue`, which is
// maintained by the example's `State`. In this case, the first `Radio`
// will start off selected because `_character` is initialized to
// `SingingCharacter.lafayette`.
//
// If the second radio button is pressed, the example's state is updated
// with `setState`, updating `_character` to `SingingCharacter.jefferson`.
// This causes the buttons to rebuild with the updated `groupValue`, and
// therefore the selection of the second button.
//
// Requires one of its ancestors to be a [Material] widget.

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

/// This Widget is the main application widget.
class MyApp extends StatelessWidget {
  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: _title,
      home: Scaffold(
        appBar: AppBar(title: const Text(_title)),
        body: Center(
          child: MyStatefulWidget(),
        ),
      ),
    );
  }
}

enum SingingCharacter { lafayette, jefferson }

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

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

class _MyStatefulWidgetState extends State<MyStatefulWidget> {
  SingingCharacter _character = SingingCharacter.lafayette;

  Widget build(BuildContext context) {
    return Column(
      children: <Widget>[
        ListTile(
          title: const Text('Lafayette'),
          leading: Radio(
            value: SingingCharacter.lafayette,
            groupValue: _character,
            onChanged: (SingingCharacter value) {
              setState(() {
                _character = value;
              });
            },
          ),
        ),
        ListTile(
          title: const Text('Thomas Jefferson'),
          leading: Radio(
            value: SingingCharacter.jefferson,
            groupValue: _character,
            onChanged: (SingingCharacter value) {
              setState(() {
                _character = value;
              });
            },
          ),
        ),
      ],
    );
  }
}