Flutter 颤振避免多次运行FutureBuilder

在我的简单代码作为新屏幕中，不幸的是

FutureBuilder

工作并从方法中获取数据两次

我不确定是什么问题，我如何才能避免

class LessonDetail extends StatefulWidget {
  final String monthKey;
  final String lessonFileKey;

  LessonDetail({@required this.monthKey, @required this.lessonFileKey});

  @override
  State<StatefulWidget> createState() {
    return _LessonDetailState(monthKey, lessonFileKey);
  }
}

class _LessonDetailState extends BaseState<LessonDetail> {
  String monthKey;
  String lessonFileKey;

  _LessonDetailState(this.monthKey, this.lessonFileKey);


  @override
  Widget build(BuildContext context) {
    return Directionality(
      textDirection: TextDirection.rtl,
      child: Scaffold(
        body: FutureBuilder(
            future: _getLessonDetail(),
            builder: (context, snapshot) {
              if (snapshot.connectionState == ConnectionState.done) {
                PlayLessonResponse response = snapshot.data;
                print(response);
              }

              return Center(
                child: CircularProgressIndicator(),
              );
            }),
      ),
    );
  }

  Future<PlayLessonResponse> _getLessonDetail() async {

    AudioList audioList = AudioList(
      'http://www.sample.com',
      'aaaaa'
    );
    List<AudioList> lst = [audioList,audioList,audioList];

    PlayLessonResponse response = PlayLessonResponse(
        2,
        '',
        'http://www.sample.com',
        '2',
        lst,
        1,
        'ssss'
    );


    print('++++++++++++++++++++');
    return response;
  }
}

---

正如@Ricardo所说，您不应该直接在FutureBuilder的future方法中调用函数

相反，您应该首先在init状态下运行函数，并将响应存储在新变量中。然后才将变量分配给FutureBuilder的未来

代码示例：

class LessonDetail extends StatefulWidget {
  final String monthKey;
  final String lessonFileKey;

  LessonDetail({@required this.monthKey, @required this.lessonFileKey});

  @override
  State<StatefulWidget> createState() {
    return _LessonDetailState(monthKey, lessonFileKey);
  }
}

class _LessonDetailState extends BaseState<LessonDetail> {
  String monthKey;
  String lessonFileKey;
  Future<PlayLesssonResponse> _myResponse; //added this line

  _LessonDetailState(this.monthKey, this.lessonFileKey);

 @override
  void initState() {
    _myResponse = _getLessonDetail();  // added this line
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Directionality(
      textDirection: TextDirection.rtl,
      child: Scaffold(
        body: FutureBuilder(
            future: _myResponse,  //use _myResponse variable here
            builder: (context, snapshot) {
              if (snapshot.connectionState == ConnectionState.done) {
                PlayLessonResponse response = snapshot.data;
                print(response);
              }

              return Center(
                child: CircularProgressIndicator(),
              );
            }),
      ),
    );
  }

  Future<PlayLessonResponse> _getLessonDetail() async {

    AudioList audioList = AudioList(
      'http://www.sample.com',
      'aaaaa'
    );
    List<AudioList> lst = [audioList,audioList,audioList];

    PlayLessonResponse response = PlayLessonResponse(
        2,
        '',
        'http://www.sample.com',
        '2',
        lst,
        1,
        'ssss'
    );


    print('++++++++++++++++++++');
    return response;
  }
}

class LessonDetail扩展了StatefulWidget{
最终字符串蒙特基；
最后一个字符串lessonFileKey；
LessonDetail（{@required this.monthKey，@required this.lessonFileKey}）；
@凌驾
状态createState（）{
返回LessonDetailState（monthKey，lessonFileKey）；
}
}
类_LessonDetailState扩展了BaseState{
斯特林·蒙特基；
字符串lessonFileKey；
Future _myResponse；//添加了此行
_LessonDetailState（this.monthKey，this.lessonFileKey）；
@凌驾
void initState（）{
_myResponse=\u getLessonDetail（）；//添加了此行
super.initState（）；
}
@凌驾
小部件构建（构建上下文）{
返回方向性(
textDirection:textDirection.rtl，
孩子：脚手架(
正文：未来建设者(
future:\u myResponse，//在此处使用\u myResponse变量
生成器：（上下文，快照）{
if（snapshot.connectionState==connectionState.done）{
PlayLessonResponse=snapshot.data；
打印（回复）；
}
返回中心(
子对象：CircularProgressIndicator（），
);
}),
),
);
}
Future\u getLessonDetail（）异步{
AudioList=AudioList(
'http://www.sample.com',
“aaaaa”
);
List lst=[audioList，audioList，audioList]；
PlayLessonResponse=PlayLessonResponse(
2.
'',
'http://www.sample.com',
'2',
lst，
1.
“ssss”
);
印刷("印刷"),；
返回响应；
}
}

正如@Ricardo所说，您不应该直接在FutureBuilder的future方法中调用函数

相反，您应该首先在init状态下运行函数，并将响应存储在新变量中。然后才将变量分配给FutureBuilder的未来

代码示例：

class LessonDetail extends StatefulWidget {
  final String monthKey;
  final String lessonFileKey;

  LessonDetail({@required this.monthKey, @required this.lessonFileKey});

  @override
  State<StatefulWidget> createState() {
    return _LessonDetailState(monthKey, lessonFileKey);
  }
}

class _LessonDetailState extends BaseState<LessonDetail> {
  String monthKey;
  String lessonFileKey;
  Future<PlayLesssonResponse> _myResponse; //added this line

  _LessonDetailState(this.monthKey, this.lessonFileKey);

 @override
  void initState() {
    _myResponse = _getLessonDetail();  // added this line
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Directionality(
      textDirection: TextDirection.rtl,
      child: Scaffold(
        body: FutureBuilder(
            future: _myResponse,  //use _myResponse variable here
            builder: (context, snapshot) {
              if (snapshot.connectionState == ConnectionState.done) {
                PlayLessonResponse response = snapshot.data;
                print(response);
              }

              return Center(
                child: CircularProgressIndicator(),
              );
            }),
      ),
    );
  }

  Future<PlayLessonResponse> _getLessonDetail() async {

    AudioList audioList = AudioList(
      'http://www.sample.com',
      'aaaaa'
    );
    List<AudioList> lst = [audioList,audioList,audioList];

    PlayLessonResponse response = PlayLessonResponse(
        2,
        '',
        'http://www.sample.com',
        '2',
        lst,
        1,
        'ssss'
    );


    print('++++++++++++++++++++');
    return response;
  }
}

class LessonDetail扩展了StatefulWidget{
最终字符串蒙特基；
最后一个字符串lessonFileKey；
LessonDetail（{@required this.monthKey，@required this.lessonFileKey}）；
@凌驾
状态createState（）{
返回LessonDetailState（monthKey，lessonFileKey）；
}
}
类_LessonDetailState扩展了BaseState{
斯特林·蒙特基；
字符串lessonFileKey；
Future _myResponse；//添加了此行
_LessonDetailState（this.monthKey，this.lessonFileKey）；
@凌驾
void initState（）{
_myResponse=\u getLessonDetail（）；//添加了此行
super.initState（）；
}
@凌驾
小部件构建（构建上下文）{
返回方向性(
textDirection:textDirection.rtl，
孩子：脚手架(
正文：未来建设者(
future:\u myResponse，//在此处使用\u myResponse变量
生成器：（上下文，快照）{
if（snapshot.connectionState==connectionState.done）{
PlayLessonResponse=snapshot.data；
打印（回复）；
}
返回中心(
子对象：CircularProgressIndicator（），
);
}),
),
);
}
Future\u getLessonDetail（）异步{
AudioList=AudioList(
'http://www.sample.com',
“aaaaa”
);
List lst=[audioList，audioList，audioList]；
PlayLessonResponse=PlayLessonResponse(
2.
'',
'http://www.sample.com',
'2',
lst，
1.
“ssss”
);
印刷("印刷"),；
返回响应；
}
}

你能尝试使用

builder：（BuildContext context，asyncsapshot snapshot）{

@TinusJackson没有任何变化那么我不确定，期待着答案，考虑

BaseState

中发生了什么？@TinusJackson我用

BaseState

类内容更新了代码你能尝试使用

builder:（BuildContext上下文，异步快照）{

@TinusJackson没有任何变化那么我不确定，期待着答案，尽管

BaseState

？@TinusJackson我用

BaseState

类内容更新了代码这东西是金子！遗憾的是，即使是flifter官方文档也没有培养出这种方法……太棒了，谢谢！这东西是金子！遗憾的是flutt呃，官方文件并没有培养这种方法……太棒了，谢谢！

class LessonDetail extends StatefulWidget {
  final String monthKey;
  final String lessonFileKey;

  LessonDetail({@required this.monthKey, @required this.lessonFileKey});

  @override
  State<StatefulWidget> createState() {
    return _LessonDetailState(monthKey, lessonFileKey);
  }
}

class _LessonDetailState extends BaseState<LessonDetail> {
  String monthKey;
  String lessonFileKey;
  Future<PlayLesssonResponse> _myResponse; //added this line

  _LessonDetailState(this.monthKey, this.lessonFileKey);

 @override
  void initState() {
    _myResponse = _getLessonDetail();  // added this line
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Directionality(
      textDirection: TextDirection.rtl,
      child: Scaffold(
        body: FutureBuilder(
            future: _myResponse,  //use _myResponse variable here
            builder: (context, snapshot) {
              if (snapshot.connectionState == ConnectionState.done) {
                PlayLessonResponse response = snapshot.data;
                print(response);
              }

              return Center(
                child: CircularProgressIndicator(),
              );
            }),
      ),
    );
  }

  Future<PlayLessonResponse> _getLessonDetail() async {

    AudioList audioList = AudioList(
      'http://www.sample.com',
      'aaaaa'
    );
    List<AudioList> lst = [audioList,audioList,audioList];

    PlayLessonResponse response = PlayLessonResponse(
        2,
        '',
        'http://www.sample.com',
        '2',
        lst,
        1,
        'ssss'
    );


    print('++++++++++++++++++++');
    return response;
  }
}