What is the difference between Expanded and Flexible widgets?

Both Expanded and Flexible widgets are used in Flutter to control how a child widget should occupy available space within a parent’s layout. They are particularly useful in Row and Column widgets when you want to distribute available space among multiple children. Despite their similar purposes, there are some key differences between Expanded and Flexible:

  1. Expanded Widget:
  • The Expanded widget is a type of Flexible widget but with a flex factor set to 1. It consumes any available space left after all non-flexible widgets have been laid out.
  • The Expanded widget is commonly used to make a child widget take up the remaining available space within a Row or Column after other children with fixed sizes have been laid out.
  • If there are multiple Expanded widgets in the same parent, they will share the available space equally (since they all have the same flex factor).

Example of Expanded widget:

Row(
  children: [
    Text('Left'),
    Expanded(
      child: Container(
        color: Colors.blue,
      ),
    ),
    Text('Right'),
  ],
)
  1. Flexible Widget:
  • The Flexible widget is more flexible (pun intended) than Expanded in that it allows you to set a custom flex factor. The flex factor determines the ratio of available space that the child should occupy relative to other Flexible widgets within the same parent.
  • By setting different flex values for multiple Flexible widgets in the same parent, you can control how the available space is distributed among them. The higher the flex value, the more space that Flexible widget will take relative to others.

Example of Flexible widget:

Row(
  children: [
    Flexible(
      flex: 2,
      child: Container(
        color: Colors.red,
      ),
    ),
    Flexible(
      flex: 3,
      child: Container(
        color: Colors.green,
      ),
    ),
  ],
)

In summary, both Expanded and Flexible are used to control the distribution of available space within a parent layout. Expanded is a specialized version of Flexible with a flex factor of 1 and is commonly used to take up the remaining space after other non-flexible children are laid out. On the other hand, Flexible allows you to set a custom flex factor, enabling you to define how much space each Flexible widget should occupy relative to others in the same parent.

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