Adding a component to the display list

You can add an object to a DisplayObjectContainer object by calling the container's addChild() or addChildAt() method. In the case of the Stage, you can also add an object to its display list during authoring by creating it, or in the case of components, by dragging it to the Stage from the Components panel. To add an object to a container with ActionScript, first create an instance of it by invoking its constructor with the new operator and then call the addChild() or addChildAt() method to place it on the Stage and in the display list. The addChild() method places the object at the next position in the display list, while addChildAt() specifies the position at which to add the object. If you specify a position that is already occupied, the object at that position, and those at higher positions, move up by 1. The numChildren property of a DisplayObjectContainer object contains the number of display objects that it contains. You can retrieve an object from the display list by calling the getChildAt() method and specifying the position, or if you know the name of the object, by calling the getChildByName() method.

NOTE

When you add a component with ActionScript, you must assign a name to it's name property if you want to access it by name in the display list.

The following example displays the names and positions of three components in the display list. First, drag a NumericStepper, a Button, and a ComboBox to the Stage so that they overlap each other and give them instance names of aNs, aButton, and aCb. Then add the following code to the Actions panel on the Frame 1 of the Timeline:

var i:int = 0;
while(i < numChildren) {
    trace(getChildAt(i).name + " is at position: " + i++);
}

You should see the following lines in the Output panel:

aNs is at position: 0
aButton is at position: 1
aCb is at position: 2

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