8/19/2023 0 Comments Flutter form dropdown list![]() ![]() See the code below that shows how to do it: import 'package:flutter/material. Useful if you don't want Please choose a location to remain an option. Pass something to hint: paremter and set selectedLocation to null (to satisfy value = null condition). Might be useful if you want to let the user re-select Please choose a location option. Add another widget that has the value (to satisfy items.where((DropdownMenuItem item) => item.value = value).length = 1). This is because your list still does not contain _selectedLocation's value. To fix the issue, we first need to set a value on each DropdownMenuItem (so that something could be passed to onChanged callback): return DropdownMenuItem( Verify this by setting _selectedLocation to null - the app should run. ![]() Since null != _selectedLocation, last condition fails. Instead, all the widgets have their value set to null. The way code is presented, there is not a DropdownMenuItem widget that has a value of _selectedLocation. There must be exactly one widget that has this value. PHP and MySQL database are used at the back end to generate JSON data. In this example, we have a list of countries in DropDownButton (), and whenever a user chooses one country from that list, the list of the city gets updated automatically by fetching JSON data from the server. Then, check how many items matching it were found. How to Add Items on Dropdown Button from REST API in Flutter. But I reccommend you to look another approach for this case for a better usability, like a dialog where you can select multiple options: Is there an. You will also need to have an option to finalize the selection. Find all that have a value that's equal to _selectedLocation. And it should have its own onTap method, so the DropdownMenuItem onTap wont trigger and select the option, dismissing the dropdown. Note that this is DropdownButton's value, not DropdownMenuItem's value. A value ( _selectedLocation) was also given.Items (a list of DropdownMenuItem widgets) were provided.We’ve explored the fundaments of the DropdownButton and DropdownMenuItem widget in Flutter.For the solution, scroll to the end of the answer.įirst of all, let's investigate what the error says (I have cited the error that's thrown with Flutter 1.2, but the idea is the same):įailed assertion: line 560 pos 15: 'items = null || items.isEmpty || value = null || items.where((DropdownMenuItem item) => item.value = value).length = 1': is not true. if you tried the above code it will work,if you want to add new element simply add that element to your list e.g deviceTypes in above code,so that the new element gets reflected in the drop down,whenever the drop down list is rendered on screen it fetches the newlist. Usage In the pubspec. This widget extend TextField and has a similar behavior as TextFormField. SelectedItemBuilder: (BuildContext context) => _animals It shows a list of options in a dropdown menu. Padding: const EdgeInsets.symmetric(vertical: 5, horizontal: 15),īorderRadius: BorderRadius.circular(30)), define a list of options for the dropdownįinal List _animals = The full source code in main.dart with explanations: // main.dartĬonst MyApp() : super(key: createState() => _HomePageState() You can find more information about the widget in the documentation. Place the DropdownButton widget inside a DropdownButtonHideUnderline widget: Advertisements DropdownButtonHideUnderline( Set the underline parameter to an empty Container: underline: Container()Ģ. Their placement varies based on the element that opens them. Hiding the underlineīelow are two different ways to remove the underline of a DropdownButton.ġ. DropDownState ( DropDown ( bottomSheetTitle: const Text ( kCities, style: TextStyle ( fontWeight: FontWeight.bold, fontSize: 20. Dropdown menus display a list of options, triggered by an icon, button, or action. We have created a custom class Item with name and icon param thatll keep info of one item of dropdown. As we have set our theme and change debug banner property of Application. After that open main.dart file and edit it. You can set the width for a DropdownButton by setting its isExpanded parameter to true and wrapping it inside a fixed-size Container or SIzedBox. Create a new project from File New Flutter Project with your development IDE. The type of the value and the type specialized for each DropdownMenuItem must be the same. The items of the DropdownButton are implemented by using a list of DropdownMenuItem widgets: Advertisements DropdownButton( The selected item will be displayed on the button when the menu disappears. ![]() When a DropdownButton widget gets pressed, a menu with items will show up and let the user select one item from them. ![]()
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