Flutter上如何用pop获取返回值？

Question

我想知道如何在 Flutter 上使用 pop 获取两个值。我尝试编写代码。但我得到了异常“必须向文本小部件提供非空字符串。”

这是代码。

第一屏

                      ElevatedButton(
                        child: const Text('move to second screen'),
                        style: ElevatedButton.styleFrom(
                            primary: Colors.orange, onPrimary: Colors.white),
                        onPressed: () async {
                          final List<String> _response =
                              await Navigator.pushNamed(
                                  context, '/adminCategoryPicker');
                          emoji = _response[0];
                          emojiName = _response[1];
                        },
                      ),

第二屏

return Card(
                  child: ListTile(
                    leading: Text(targetElectricsEmojiLists[index]),
                    title: Text(targetElectricsNameLists[index]),
                    onTap: () {
                      setState(() {
                        _selectedName = targetElectricsNameLists[index];
                        _selectedEmoji = targetElectricsEmojiLists[index];
                      });
                      Navigator.pop(
                        context,
                        {_selectedName, _selectedEmoji},
                      );
                    },
                  ),
                );

我认为这个问题在下面部分。您知道编写代码的其他方法吗？

第一屏

onPressed: () async {
     final List<String> _response =
     await Navigator.pushNamed(
          context, '/goToSecondScreen');
           emoji = _response[0];
           emojiName = _response[1];
},

第二屏

Navigator.pop(
       context,
       {_selectedName, _selectedEmoji},
);

---

我改变了代码。此外，我得到了错误。

[错误：flutter/lib/ui/ui_dart_state.cc(186)] 未处理的异常：类型“MaterialPageRoute”不是类型“Route<List>”的子类型？在类型转换中

第一屏

ElevatedButton(
                        child: const Text('move to second screen'),
                        style: ElevatedButton.styleFrom(
                            primary: Colors.orange, onPrimary: Colors.white),
                        onPressed: () async {
                          final List<String> _response =
                              await Navigator.pushNamed(
                                  context, '/adminCategoryPicker');
                          emojiName = _response[0];
                          emoji = _response[1];
                        },
                      ),

第二屏

return Card(
                  child: ListTile(
                    leading: Text(targetElectricsEmojiLists[index] ?? 'null'),
                    title: Text(targetElectricsNameLists[index] ?? 'null'),
                    onTap: () {
                      setState(() {
                        _selectedName = targetElectricsNameLists[index];
                        _selectedEmoji = targetElectricsEmojiLists[index];
                      });
                      Navigator.pop(
                        context,
                        [_selectedName, _selectedEmoji],
                      );
                    },
                  ),
                );

Answer 1

你可以尝试下面的方法

第一屏

                 ElevatedButton(
                    child: const Text('move to second screen'),
                    style: ElevatedButton.styleFrom(
                        primary: Colors.orange, onPrimary: Colors.white),
                    onPressed: () {
                       
                        Navigator.pushNamed(context,'/adminCategoryPicker')
                        .then((value) 
                          {
                             emoji = (value as Map)['emoji'];
                             emojiName =  (value as Map)['emojiName'];
                          });
                       },
                     ),

第二屏

return Card(
                  child: ListTile(
                    leading: Text(targetElectricsEmojiLists[index]),
                    title: Text(targetElectricsNameLists[index]),
                    onTap: () {
                      setState(() {
                        _selectedName = targetElectricsNameLists[index];
                        _selectedEmoji = targetElectricsEmojiLists[index];
                      });
                      Navigator.pop(
                        context,{'emoji':_selectedName,'emojiName':_selectedEmoji}
                      );
                    },
                  ),
                );