如何在 flutter 中调用 Stream Builder 中的导航器？

Question

我有一个问题，当我尝试将导航器 pop() 方法放入字符串生成器中时出现此错误：setState() or markNeedsBuild() called during build.

我了解到您无法在流生成器中调用导航器，所以有人知道如何解决这个问题吗？

这是我的代码：

return Scaffold(
      resizeToAvoidBottomPadding: false,
      body: Center(
        child: Container(
            padding: EdgeInsets.all(15),
            color: Colors.white,
            child: Column(
              children: <Widget>[
                SizedBox(height: 55),
                SvgPicture.asset('images/svg_example.svg'),
                SizedBox(height: 55),
                Text("Login App",
                    style: TextStyle(
                        fontWeight: FontWeight.bold, color: Colors.black)),
                SizedBox(height: 40),
                emailField,
                SizedBox(height: 45),
                passwordField,
                SizedBox(height: 45),
                loginButton,
                SizedBox(height: 15),
                StreamBuilder<ApiResponse<LoginResponse>>(
                  stream: userBloc.authenticationUserStream,
                  builder: (context,
                      AsyncSnapshot<ApiResponse<LoginResponse>> snapshot) {
                    // it will observe changes on the ApiResponse<LoginResponse>
                    if (!snapshot.hasData) return Container();
                    switch (snapshot.data.status) {
                      case Status.LOADING:
                        return Loading(
                          loadingMessage: "loading",
                        );
                      case Status.COMPLETED:
                        prefs.saveTokenPref(snapshot.data.data.token);
                        prefs.saveUserPref(snapshot.data.data.user);
                        goToMain();
                        return Container(width: 0.0, height: 0.0);
                      case Status.ERROR:
                        // Here you can go to another screen after login success.
                        return Center(
                          child: Text("${snapshot.data.message}"),
                        );
                      default:
                        return Container();
                    }
                  },
                )
              ],
            )),
      ),
    );
  }

  goToMain() {
    Navigator.push(
      context,
      MaterialPageRoute(builder: (context) => MainScreen()),
    );
  }

Answer 1

好的，鉴于我的问题有一个 -1，因为有人只是想付出而不真正帮助 post 我把这个问题的答案放在这里：

您只需在 initState() 上执行此操作这将监听流本身并在 Stream Builder 之外创建 UI 逻辑。

@override
  void initState() {
    userBloc = UserBloc();

    super.initState();
    userBloc.userSubject.listen((state) {
      if (state.status == Status.COMPLETED) {
        goToMain();
      }
    });
  }

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