How to Implement Drop Down List in Flutter?

In this blog post, we will explore how to implement a drop down list in Flutter. The drop down list is a widget that allows users to select one item from a list of options.

Basic Structure

The basic structure of a drop down list in Flutter consists of three main parts:

1. DropdownButton
2. items
3. onChanged

DropdownButton

The DropdownButton is the main widget that wraps around the entire drop down list. It takes in a number of parameters, including:

• items: A list of DropdownMenuItem widgets.
• value: The currently selected item from the list.
• onChanged: A callback function that is called when a new item is selected.

items

The items parameter represents a list of DropdownMenuItem widgets. Each DropdownMenuItem widget contains two main parts:

1. child
2. value

child

The child parameter represents the visible text or icon that is displayed for each item in the list.

value

The value parameter represents the actual data associated with each item in the list. This can be any type of object, such as a string or an integer.

DropdownMenuItem(
  child: Text('A'),
  value: 'A',
)

onChanged

The onChanged parameter represents a callback function that is called when a new item is selected from the list. The function takes in a single argument, which represents the newly selected item.

DropdownButton(
  items: [
    DropdownMenuItem(
      child: Text('A'),
      value: 'A',
    ),
    DropdownMenuItem(
      child: Text('B'),
      value: 'B',
    ),
  ],
  onChanged: (value) {
    print(value);
  },
)

Example Code

Here is an example of how to implement a drop down list in Flutter:

DropdownButton(
  items: [
    DropdownMenuItem(
      child: Text('A'),
      value: 'A',
    ),
    DropdownMenuItem(
      child: Text('B'),
      value: 'B',
    ),
  ],
  onChanged: (value) {
    setState(() {
      _selectedValue = value;
    });
  },
  value: _selectedValue,
)

In this example, we have a list of two items, A and B. When an item is selected from the list, the onChanged callback function is called with the newly selected item as an argument.

Conclusion

In conclusion, implementing a drop down list in Flutter requires creating a DropdownButton widget that wraps around a list of DropdownMenuItem widgets. Each DropdownMenuItem widget contains child and value parameters, which represent the visible text or icon and actual data associated with each item, respectively. The onChanged parameter represents a callback function that is called when a new item is selected from the list.

By following these steps and using the example code provided above, you should be able to implement a drop down list in Flutter that meets your needs.