Flutter中showModalBottomSheet向上一页面传值不生效如何解决？

你代码中StatefulBuilder构造参数里的setState是弹窗自身的局部状态更新方法，仅会触发底部弹窗范围内的UI重绘，不会触发父级TestPage的重新构建，因此父页面的Text组件不会展示最新值，只有热重载触发全局重绘时才会更新显示。

以下是两种可直接落地的实现方式：

方案1：调用父页面自身的setState #

将StatefulBuilder的状态更新方法重命名避免命名冲突，修改父页面状态时调用父类自带的setState即可：

class TestPage extends StatefulWidget {
  const TestPage({Key? key}) : super(key: key);

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

class _TestPageState extends State<TestPage> {
  String textResult = "";
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          child: Padding(
            padding: const EdgeInsets.all(8.0),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                Text(textResult),
                TextButton(
                    onPressed: () {
                      showModalBottomSheet(
                        shape: RoundedRectangleBorder(
                            borderRadius: BorderRadius.only(
                                topRight: Radius.circular(24.0),
                                topLeft: Radius.circular(24.0))),
                        context: context,
                        // 将StatefulBuilder的setState重命名为setModalState，避免和父类setState冲突
                        builder: (_) => StatefulBuilder(
                            builder: (BuildContext context, StateSetter setModalState) {
                          return Container(
                            child: Column(
                              crossAxisAlignment: CrossAxisAlignment.start,
                              children: [
                                Padding(
                                  padding: const EdgeInsets.all(8.0),
                                  child: Row(
                                    mainAxisAlignment:
                                        MainAxisAlignment.spaceBetween,
                                    children: [
                                      GestureDetector(
                                        onTap: () {
                                          // 调用父页面的setState更新状态
                                          setState(() {
                                            textResult = "1";
                                          });
                                          Navigator.pop(context);
                                        },
                                        child: const Text(
                                          'Done',
                                          style: TextStyle(
                                              color: Colors.red,
                                              fontWeight: FontWeight.bold),
                                        ),
                                      ),
                                    ],
                                  ),
                                ),
                              ],
                            ),
                          );
                        }),
                      );
                    },
                    child: const Text('Press'))
              ],
            ),
          ),
        ),
      ),
    );
  }
}

方案2（更推荐）：通过弹窗返回值传参 #

showModalBottomSheet本身返回一个Future对象，关闭弹窗时可以携带返回值，父页面接收值后再更新自身状态，耦合度更低，可维护性更好：

class TestPage extends StatefulWidget {
  const TestPage({Key? key}) : super(key: key);

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

class _TestPageState extends State<TestPage> {
  String textResult = "";
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          child: Padding(
            padding: const EdgeInsets.all(8.0),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                Text(textResult),
                TextButton(
                    // 改成async方法接收弹窗返回值
                    onPressed: () async {
                      // 接收弹窗关闭时返回的结果
                      final result = await showModalBottomSheet<String>(
                        shape: RoundedRectangleBorder(
                            borderRadius: BorderRadius.only(
                                topRight: Radius.circular(24.0),
                                topLeft: Radius.circular(24.0))),
                        context: context,
                        builder: (_) => Container(
                          child: Column(
                            crossAxisAlignment: CrossAxisAlignment.start,
                            children: [
                              Padding(
                                padding: const EdgeInsets.all(8.0),
                                child: Row(
                                  mainAxisAlignment:
                                  MainAxisAlignment.spaceBetween,
                                  children: [
                                    GestureDetector(
                                      onTap: () {
                                        // 关闭弹窗时携带返回值
                                        Navigator.pop(context, "1");
                                      },
                                      child: const Text(
                                        'Done',
                                        style: TextStyle(
                                            color: Colors.red,
                                            fontWeight: FontWeight.bold),
                                      ),
                                    ),
                                  ],
                                ),
                              ),
                            ],
                          ),
                        ),
                      );
                      // 拿到返回值后更新父页面状态
                      if (result != null) {
                        setState(() {
                          textResult = result;
                        });
                      }
                    },
                    child: const Text('Press'))
              ],
            ),
          ),
        ),
      ),
    );
  }
}

内容的提问来源于stack exchange，提问作者Mohammed Nabil