从 List.map() 获取迭代索引 [英] Get iteration index from List.map()

问题描述

我在字母列表上写了一个迭代，并使用地图"将卡片放在屏幕上班级.

I wrote an iteration on list of letters and put inside cards on screen using "map" class.

在代码中你可以看到我做了一行，并使用了map"将卡片上的所有用户板打印到屏幕上.我想在里面添加一些逻辑，所以我需要获取元素的 id(用于录音事件).有没有办法做到这一点?

In the code you can see that I made a row, and using "map" printed all the userBoard on cards to the screen. I want to add some logic inside so I need to get the id of the element (for taping event). Is there a way that I can do that?

实际上，我想通过 userBoard 获取元素的特定索引.

Actually, I want to get a specific index of element over userBoard.

代码:

Widget build(BuildContext context) {
    return Row(
      mainAxisAlignment: MainAxisAlignment.spaceEvenly,
      children: <Widget>[
            Row(
              children: userBoard
                  .map((element) => Stack(children: <Widget>[
                        Align(
                          alignment: Alignment(0, -0.6),
                          child: GestureDetector(
                            onTap: (() {
                              setState(() {
                                // print("element=${element.toString()}");
                                // print("element=${userBoard[element]}");
                              });
                            }),
                            child: SizedBox(
                              width: 40,
                              height: 60,
                              child: Card(
                                  shape: RoundedRectangleBorder(
                                    borderRadius: BorderRadius.circular(5.0),
                                  ),
                                  child: Center(
                                    child: Text(element,
                                        style: TextStyle(fontSize: 30)),
                                  )),
                            ),
                          ),
                        )
                      ]))
                  .toList(),
            )
          ],
        ),
}

图片 - 每张卡片都是元素"；地图的.我想获取 onTap 函数的索引.

Picture - each card is "element" of the map. I want to get the indexes for the function onTap.

推荐答案

要访问索引，您需要使用 asMap 运算符.

To get access to index, you need to convert your list to a map using the asMap operator.

示例

final fruitList = ['apple', 'orange', 'mango'];
final fruitMap = fruitList.asMap(); // {0: 'apple', 1: 'orange', 2: 'mango'}

// To access 'orange' use the index 1.
final myFruit = fruitMap[1] // 'orange'

// To convert back to list
final fruitListAgain = fruitMap.values.toList();

您的代码

userBoard.asMap().map((i, element) => MapEntry(i, Stack(
  GestureDetector(onTap: () {
    setState(() {
      // print("element=${element.toString()}");
      // print("element=${userBoard[i].toString()}");
    });
  }),
))).values.toList();

这篇关于从 List.map() 获取迭代索引的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！