Flutter报错：参数类型‘String’无法赋值给‘TextEditingController?’求解决

问题根源 #

1. 参数类型不匹配：TextField的controller参数要求传入TextEditingController实例，你错误地传入了titleController.text（字符串类型）。
2. const组件引用非const变量：你给目标TextField添加了const修饰符，但titleController是State中初始化的非const变量，const组件无法访问非const成员，这也是titleController.text提示“getter未定义”的直接原因。

修复步骤 #

• 移除TextField的const关键字；
• 将controller参数的值从titleController.text改为titleController（直接传入控制器实例）。

完整修正代码 #

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

  @override
  State<AddTodoPopupCard> createState() => _AddTodoPopupCardState();
}

class _AddTodoPopupCardState extends State<AddTodoPopupCard> {
  /// {@macro add_todo_popup_card}
  final titleController = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Padding(
        padding: const EdgeInsets.all(10.0),
        child: Hero(
          tag: heroAddTodo,
          createRectTween: (begin, end) {
            return CustomRectTween(begin: begin!, end: end!);
          },
          child: Card(
            clipBehavior: Clip.antiAliasWithSaveLayer,
            color: Colors.blueGrey,
            elevation: 2,
            shape:
                RoundedRectangleBorder(borderRadius: BorderRadius.circular(10)),
            child: SizedBox(
              height: MediaQuery.of(context).size.height * 0.7,
              width: MediaQuery.of(context).size.width * 0.9,
              child: SingleChildScrollView(
                  physics: const ClampingScrollPhysics(),
                  keyboardDismissBehavior:
                      ScrollViewKeyboardDismissBehavior.onDrag,
                  child: Column(
                    children: [
                      SizedBox(
                          width: MediaQuery.of(context).size.width * 0.9,
                          height: MediaQuery.of(context).size.height * 0.25,
                          child: GestureDetector(
                            onTap: () {
                              print("Add a video picker widget");
                            },
                            child: Container(
                              color: Colors.grey[600],
                              child: const Column(
                                children: [
                                  SizedBox(height: 50),
                                  Icon(
                                    Icons.video_file_rounded,
                                    size: 56,
                                  ),
                                  SizedBox(height: 5),
                                  Text(
                                    "Upload Video",
                                    style:
                                        TextStyle(fontWeight: FontWeight.bold),
                                  )
                                ],
                              ),
                            ),
                          )),
                      Padding(
                        padding: const EdgeInsets.only(
                            top: 15, bottom: 10, left: 10, right: 10),
                        child: TextField(
                          controller: titleController,
                          style: const TextStyle(
                              fontWeight: FontWeight.bold, fontSize: 22),
                          decoration: const InputDecoration(
                              hintText: 'Click to add title',
                              border: InputBorder.none,
                              counterText: ""),
                          cursorColor: Colors.white,
                          maxLines: 2,
                          maxLength: 80,
                        ),
                      ),
                      const Divider(
                        indent: 5,
                        endIndent: 5,
                        color: Colors.white,
                        thickness: 0.2,
                      ),
                      const Padding(
                        padding: EdgeInsets.only(
                            top: 15, bottom: 10, left: 10, right: 10),
                        child: TextField(
                          style: TextStyle(
                              fontWeight: FontWeight.w300, fontSize: 14),
                          decoration: InputDecoration(
                            hintText: 'Click to add description',
                            border: InputBorder.none,
                          ),
                          cursorColor: Colors.white,
                          maxLines: 14,
                          maxLength: 800,
                        ),
                      ),
                      const Divider(
                        indent: 5,
                        endIndent: 5,
                        color: Colors.white,
                        thickness: 0.2,
                      ),
                      const SizedBox(height: 30),
                      GestureDetector(
                        onTap: () {
                          print("Upload script button pressed.");
                        },
                        child: Container(
                            padding: const EdgeInsets.only(left: 10),
                            margin: const EdgeInsets.only(right: 115),
                            height: 50,
                            child: Card(
                              elevation: 5,
                              child: const Row(
                                children: [
                                  Icon(
                                    Icons.file_present_rounded,
                                    size: 30,
                                  ),
                                  SizedBox(width: 5),
                                  Text("Click to upload your script")
                                ],
                              ),
                            )),
                      ),
                      const SizedBox(height: 30),
                      GestureDetector(
                        onTap: () async {
                          print("object");
                        },
                        child: Container(
                          alignment: Alignment.center,
                          width: MediaQuery.of(context).size.width * 0.9,
                          height: 50,
                          color: Colors.grey[800],
                          child: Text(
                            'Submit.',
                            style: const TextStyle(
                                fontSize: 28, fontWeight: FontWeight.bold),
                            textAlign: TextAlign.center,
                          )
                              .animate(
                                onPlay: (controller) =>
                                    controller.repeat(reverse: true),
                              )
                              .shimmer(
                                  color: Colors.blue,
                                  duration: const Duration(seconds: 3)),
                        ),
                      )
                    ],
                  )),
            ),
          ),
        ),
      ),
    );
  }
}

内容的提问来源于stack exchange，提问作者Muhammed Shoaib