无法在Flutter中修改列表项/元素 [英] Cannot modify a List Item/Element in Flutter

问题描述

我有一个初始化如下的列表: 这在main之外(因此它是全局的，因为许多其他类都需要访问它).

I have a list that is initialised as follows: This is outside of main (so it is global as many other classes need to access it).

List mainMenuList = [];

然后在其中填充购物物品.

It is then populated with shopping items.

如此

mainMenuList.elementAt[counter].shoppingPrice; 

或

print(mainMenuList.elementAt[counter].shoppingPrice);

给出"4.00"；

但是如果我想增加或更改该元素的值，则会收到错误消息:

but if I wanted to increment or change that element's value, I get an error:

flutter: Unsupported operation: read-only

因此，例如，我正在尝试为其添加补充:

So, for example, I'm trying to add supplements to it:

mainMenuList[listItemIndicator]['ItemPrice'] += supplementsList[supplementCounter]['SupplementPrice']);

我收到以下错误:

flutter:不支持的操作:只读

flutter: Unsupported operation: read-only

所以即使我忘记了补品..如果我做了类似的事情:

So even if I forget about supplements.. if I did something like:

mainMenuList[listItemIndicator]['ItemPrice'] = 1.00; 

我遇到同样的错误

非常感谢！

推荐答案

您尝试在此处将List与键值泛型配合使用，以便上面的代码显示

You are trying to use key-value generic with List here or so the above code shows

mainMenuList[listItemIndicator]['ItemPrice'] = 1.00;   //incorrect way of using List

您需要为此使用HashMap或LinkedMap.

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