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Adapting to Flexible UI Design Using CustomMultiChildLayout in Flutter

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Nidhi Sorathiya

September 15, 2023

Nidhi Sorathiya

September 15, 2023

Flutter creates an opportunity for developers to build complex and attractive UI designs. Among the key widgets enabling such sophistication is the CustomMultiChildLayout. Essentially, The CustomMultiChildLayout class is an advanced multi-child layout widget for managing complex relationships among multiple widgets in a flexible and efficient manner. It allows one to position multiple children within itself according to the demands of the UI design.

Its distinguishing factor as compared to other UI layouts, like the Stack widget, is its ability to handle complex custom layouts. Unlike a Stack widget which can support only a single child per position, CustomMultiChildLayout in Flutter allows you to operate with multiple widgets.

The Structure of CustomMultiChildLayout

The CustomMultiChildLayout in Flutter is essentially made up of two major components: layoutDelegate and children. Each child within this layout has its ID represented by LayoutId id, and you can modify each child manually as well as position it through axis dependent methods.

Take, for example, the following simple code snippet that creates a CustomMultiChildLayout:

The YourDelegate in the code snippet needs to be an instance of a class that extends MultiChildLayoutDelegate. This delegate class hosts the logic that positions the children in the layout.

The Role of CustomMultiChildLayout in Flutter

Utilizing CustomMultiChildLayout in Flutter has become substantial due to its powerful flexibility. This mighty layout widget shines particularly when dealing with the needs of advanced layouts with complex relationships and flexible rules about their arrangement.

For instance, imagine you have multiple widgets that need to be aligned with one or another edge of their parent widget without collision. Or consider a situation where you need to position the middle widget and its final offset position, keep the widget width the same, and place the final widget on the bottom of the layout. In cases like these, the CustomMultiChildLayout becomes a perfect choice.

It's also worth noting that CustomMultiChildLayout is writing direction agnostic. It means the positioning is independent of the text direction, thus giving you freedom to make your layouts more universal.

Detailed Exploration of CustomMultiChildLayout

The primary components of the CustomMultiChildLayout are its layoutDelegate and children. Let’s dive a little deeper into these properties:

  • layoutDelegate: Manages the layout algorithm for the CustomMultiChildLayout. It is responsible for the final position and size of the child widgets.
  • children: A list comprising of LayoutId widgets, each of which contains an id and a child. The id is used by the layoutDelegate to determine the position in the final widget layout. Each of the LayoutId widgets has an associated id to identify it and to determine its alignment.

Example Scene: Unpacking a CustomMultiChildLayout

To better understand the use and structuring of the CustomMultiChildLayout, let's consider a simple example of creating a CustomMultiChildLayout with two LayoutIds that should be positioned one below the other.

This code displays a blue square on top and a red square below it. The management of the layout and its change on different factors is a fundamental factor in building more complex layouts.

General Tips and Tricks for Using CustomMultiChildLayout

To create advanced layouts effectively, remember the following points:

  1. CustomMultiChildLayout provides an effective way to link the layout of multiple children. The layout of each child is dependent on the position or size of the other children.
  2. Do remember to check the size of each widget with the help of Size.sizeOf(). This method helps to ensure that the layout does not overflow from its parent or assigned size.
  3. Keep in mind the usage of BoxConstraints. It helps specify the constraints according to which the widgets will be rendered on the screen.
  4. Remember: The layoutDelegate has the supreme authority to manipulate the children under CustomMultiChildLayout. Make sure to position them suitably.


The use of CustomMultiChildLayout in Flutter not only advances the look and feel of your application but also provides an efficient way of handling complex relationships between widgets on various axes. This is why understanding and harnessing it is so crucial for every Flutter developer aiming to create advanced and professional layouts. Hopefully, this comprehensive blog adds to your understanding and is a helpful resource for your future Flutter development.

Frequently asked questions

Frequently asked questions

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