必須先分配不可為空的區域變數“iconData”才能在flutter中使用？

1. 我正在嘗試在 IconData 和 Icon Color 中添加 switch case 陳述句，當我使用它們時會拋出一些錯誤
2. 必須先分配不可為空的區域變數“iconData”，然后才能使用它。嘗試給它一個初始化運算式，或者確保在每個執行路徑上都分配了它

TodoAddPage.dart

 class TodoCardPage extends StatefulWidget {
      const TodoCardPage({
        Key? key,
        required this.title,
        required this.iconData,
        required this.iconColor,
      }) : super(key: key);
      final String title;
      final IconData iconData;
      final Color iconColor;

在主頁我嘗試使用 homePage.dart

ListView.builder(
                itemCount: (snapshot.data! as QuerySnapshot).docs.length,
                itemBuilder: (context, index) {
                  IconData iconData;
                  Color iconColor;
                  Map<String, dynamic> document =
                      (snapshot.data! as QuerySnapshot).docs[index].data()
                          as Map<String, dynamic>;

                  return TodoCardPage(
                      title: document["title"] == null
                          ? "Hey There"
                          : document["title"],
                      iconData: iconData,
                      iconColor: iconColor,
                      time: "10 PM",
                      value: true,
                      iconBgColor: Colors.white);
                });

uj5u.com熱心網友回復：

你的 iconData 和 iconColor 都沒有初始化。嘗試

IconData iconData = Icons.add; // your icon
Color iconColor = Colors.blue; // your color

uj5u.com熱心網友回復：

我剛剛發現這個錯誤非常感謝你們，正確的答案是

ListView.builder(
                itemCount: (snapshot.data! as QuerySnapshot).docs.length,
                itemBuilder: (context, index) {
                  IconData iconData;
                  Color iconColor;
                  Map<String, dynamic> document =
                      (snapshot.data! as QuerySnapshot).docs[index].data()
                          as Map<String, dynamic>;
                  switch (document["category"]) {
                    case "Work":
                      iconData = (Icons.breakfast_dining);
                      iconColor = Colors.red;
                      break;
                    default:
                      iconData = (Icons.add);
                      iconColor = Color.fromARGB(255, 56, 46, 196);
                  }
                  return TodoCardPage(
                      title: document["title"] == null
                          ? "Hey There"
                          : document["title"],
                      iconData: iconData,
                      iconColor: iconColor,
                      time: "10 PM",
                      value: true,
                      iconBgColor: Colors.white);
                });

uj5u.com熱心網友回復：

在添加之前，有必要在那里宣告 Icon 類。

嘗試這個

class TodoCardPage extends StatefulWidget {
      const TodoCardPage({
        Key? key,
        required this.title,
        required this.iconData,
        required this.iconColor,
      }) : super(key: key);
      final String title;
      final Icon myIcon;
      final Color iconColor;

嘗試這個

ListView.builder(
                itemCount: (snapshot.data! as QuerySnapshot).docs.length,
                itemBuilder: (context, index) {
                  IconData iconData;
                  Color iconColor;
                  Map<String, dynamic> document =
                      (snapshot.data! as QuerySnapshot).docs[index].data()
                          as Map<String, dynamic>;
                  switch (document["category"]) {
                    case "Work":
                      iconData = (Icons.breakfast_dining);
                      iconColor = Colors.red;
                      break;
                    default:
                      iconData = (Icons.add);
                      iconColor = Color.fromARGB(255, 56, 46, 196);
                  }
                  return TodoCardPage(
                      title: document["title"] == null
                          ? "Hey There"
                          : document["title"],
                      iconData: myIcon(iconData),// this line
                      iconColor: iconColor,
                      time: "10 PM",
                      value: true,
                      iconBgColor: Colors.white);
                });

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