Flex 2 Developer's Guide > Building User Interfaces for
Flex Applications > Introducing Containers > About containers > About container layout

About container layout

Containers have predefined navigation and layout rules, so you do not have to spend time defining these. Instead, you can concentrate on the information that you deliver, and the options that you provide for your users, and not worry about implementing all the details of user action and application response. In this way, Flex provides the structure that lets you quickly and easily develop an application with a rich set of features and interactions.

Predefined layout rules also offer the advantage that your users soon grow accustomed to them. That is, by standardizing the rules of user interaction, your users do not have to think about how to navigate the application, but can instead concentrate on the content that the application offers.

Different containers support different layout rules:

All containers, except the Canvas container, support automatic layout. With this type of layout you do not specify the position of the children of the container. Instead, you control the positions by selecting the container type; by setting the order of the container's children; and by specifying properties, such as gaps, and controls, such as Spacers. For example, to lay out children horizontally in a box, you use the HBox container.
The Canvas container, and optionally the Application and Panel containers, use absolute layout, where you explicitly specify the children's x and y positions. Alternatively, you can use constraint-based layout to anchor the sides or center of the children relative to the parent.

Absolute layout provides a greater level of control over sizing and positioning than does automatic layout; for example, you can use it to overlay one control on another. But absolute layout provides this control at the cost of making you specify positions in detail.

For more information on layout, see Sizing and Positioning Components.

Flex 2.01

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