By default, Flex displays the Loading progress bar while it initializes an application. Only after all of the components in the application are initialized and laid out does Flex display any portion of the application. Using ordered creation, you can customize this experience and change the user's perception of how quickly the application starts.

During initialization, Flex first creates all the containers, and then fills in each container with its children and data. Finally, Flex displays the application in its entirety. This causes the user to wait for the entire application to load before beginning to interact with it.

However, you can instruct Flex to display the children of each container as its children are created rather than waiting for the entire application to finish loading. You do this using a technique called ordered creation.

The following example shows a complex application that contains a single container at the top, and four containers across the bottom. This application implements ordered creation so that the contents of each container become visible before the entire application is finished loading.

In this example, the image on the left shows the application after the first container is populated with its children and data, but before the remaining four containers are populated. The image on the right shows the final state of the application.

If this application did not use ordered creation, Flex would not display anything until all components in all five of the containers were created, resulting in a longer perceived start-up time.

To gradually display children of each container, you add them to an instantiation queue. The Adding containers to the queue section describes how to add containers to the queue so that you can improve perceived layout performance of your Flex applications.