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Flutter – How to define Dropdown Menu SearchCallBack

I want to implement a text search in Dropdown Flutter/Dart.

I want to use Flutter/Dart DropdownMenu class.

I don’t want to use DropDownButton b/c it does not have a search.

The DropdownMenu Search class has SearchCallBack.

The DropdownMenu class has 3 key things: List, Controller, and SearchCallBack.

I want to use Controller to search the Controller’s input text.

The SearchCallBack has two things: list and query.

I am not certain how to define the SearchCallBack correctly.

Could you please provide example of SearchCallBack.

Thank You

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2

Answers


  1. 0

    Imagine a function that takes a list of DropdownMenuEntrys ("entries") and a String ("query"), and returns an int for the index of a DropdownMenuEntry in the list that matches the string. This is the function you are passing as the SearchCallback parameter. If you leave it blank, it will default to a function that returns the index of first entry that contains the query anywhere in it. You can write your own function to customize the search. For example, here is a function you could write that returns the index of the first entry that matches the query exactly.

    DropdownMenu<Text>(
  searchCallback: (List<DropdownMenuEntry<Text>> entries, String query) {
    if (query.isEmpty) {
      return null;
    }
    final int index = entries.indexWhere((DropdownMenuEntry<Text> entry) => entry.label == query);

    return index != -1 ? index : null;
  },
  dropdownMenuEntries: const <DropdownMenuEntry<Text>>[],
)
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  2. 0

    I used flutter auto complete widget like below and also I implementing this using TextEditingController also in generic clean way let me know if you have any questions

    class DropdownSearch<T extends DropAble> extends StatelessWidget {
  final TextEditingController textController;
  final List<T> items;
  final void Function(T) onSuggestionSelected;
  final bool required;
  final String placeHolder;
  final String label;
  final String? Function(T?) validator;

  const DropdownSearch({
    super.key,
    required this.textController,
    required this.items,
    required this.onSuggestionSelected,
    this.required = false,
    this.label = "",
    this.placeHolder = "",
    required this.validator,
  });

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.symmetric(vertical: 14),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Text(
            "${required ? "* " : ""}$label",
            style: Theme.of(context).textTheme.labelMedium,
          ),
          const SizedBox(
            height: 14,
          ),
          RawAutocomplete<String>(
            optionsBuilder: (TextEditingValue textEditingValue) {
            return  items.map((e)=>e.name ?? "").toList()
                  .where((item) =>
                  (item).toLowerCase().contains(textEditingValue.text.toLowerCase()))
                  .toList();
            },
            onSelected: (String selection) {
              textController.text = selection;
              T? item = items.firstWhereOrNull((element) => element.name == selection);
              if (item != null) {
                onSuggestionSelected(item);
              }
            },
            fieldViewBuilder: (
                BuildContext context,
                TextEditingController textEditingController,
                FocusNode focusNode,
                VoidCallback onFieldSubmitted,
                ) {
              return TextFormField(
                controller: textEditingController,
                decoration:  InputDecoration(
                  hintText: placeHolder,
                ),
                focusNode: focusNode,
                onFieldSubmitted: (String value) {
                  T? item = items.firstWhereOrNull((element) => element.name == value);
                  onFieldSubmitted();
                  if (item != null) {
                    onSuggestionSelected(item);
                  }
                },
               // validator: vali,
              );
            },
            optionsViewBuilder: (
                BuildContext context,
                AutocompleteOnSelected<String> onSelected,
                Iterable<String> options,
                ) {
              return Align(
                alignment: Get.locale?.languageCode == "ar" ? Alignment.topRight : Alignment.topLeft,
                child: Material(
                  elevation: 4.0,
                  child: SizedBox(
                    width: Get.width-70,
                    child: ListView.builder(
                      shrinkWrap: true,
                      padding: const EdgeInsets.all(8.0),
                      itemCount: options.length,
                      itemBuilder: (BuildContext context, int index) {
                        final  option = options.elementAt(index);
                        return GestureDetector(
                          onTap: () {
                            textController.text = option;
                            onSelected(option);
                            T? item = items.firstWhereOrNull((element) => element.name == option);
                            if(item != null){
                              onSuggestionSelected(item);
                            }
                          },
                          child: ListTile(
                            title: Text(option),
                          ),
                        );
                      },
                    ),
                  ),
                ),
              );
            },
          ),
          const SizedBox(
            height: 14,
          ),
        ],
      ),
    );
  }
}
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