Google Dart仅显示特定的DropDown子元素

问题描述

我试图通过隐藏一些选择从下拉列表中只获取某些值。显然我不能超过数组索引3或没有显示，显然不低于索引0.我试图隐藏下拉列表中的前三个选择。任何想法将不胜感激。如果您需要更多信息，请告诉我们。

打印输出：

1. 选择一个选项 - 禁用


2. 选择1


3. 选择2


4. 选择3


5. li>
   
6. 选择5

b
$ b

 列表< Map> _predefinedFilterList; 
 _predefinedFilterList = jsonObject [jsonResponse] as List< Map> ;; 
 
 for（Map filterMap in _predefinedFilterList）{
 dropDownEl.children.add（new OptionElement（data：filterMap [displayName]））; 
 
 print（Test：+ filterMap [displayName]）; 
 
 // dropDownEl.children [0] .hidden = true; 
 // dropDownEl.children [1] .hidden = true; 
 // dropDownEl.children [2] .hidden = true; 
} 
  




解决方案

第三个子列表之后的项目将删除前三个列表元素。

  _predefinedFilterList.sublist（3）.forEach => print（map [displayName]））; 
  




I'm attempting to get only certain values from a drop-down by hiding a select few. Apparently I cannot go over an array index of 3 or nothing shows up and obviously not below an index of 0. I'm trying to hide the first three choices in the drop-down. Any ideas would be appreciated. Please let me know if you need more information.

The printout:

1. Select a choice --disabled
2. Choice 1
3. Choice 2
4. Choice 3
5. Choice 4
6. Choice 5

Code:

  List<Map> _predefinedFilterList;
_predefinedFilterList = jsonObject["jsonResponse"] as List<Map>;

for (Map filterMap in _predefinedFilterList) {
        dropDownEl.children.add(new OptionElement(data: filterMap["displayName"]));

print("Test: "+filterMap["displayName"]);

 //         dropDownEl.children[0].hidden = true;   
 //         dropDownEl.children[1].hidden = true;
//          dropDownEl.children[2].hidden = true;
      }

解决方案

This would only go over the items after the 3rd as sublist would remove the first 3 list elements.

_predefinedFilterList.sublist(3).forEach((map) => print(map["displayName"]));

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