There are four basic button types of controls: Button, LinkButton, RadioButton, and CheckBox. Although each type behaves similarly, they have different intended uses. Figure 7-2 shows instances of each type.

Figure 7-2. Button components

Of the four types, Button and LinkButton are the most similar in use. In fact, the primary difference between Button and LinkButton is purely cosmetic: buttons have borders and backgrounds and link buttons do not. However, you’ll typically use both types for similar purposes—generally to initiate some behavior when the user clicks on the button or link button. Buttons are typically more common than link buttons.

By default, buttons and link buttons respond to every click in the same way. However, you can set the toggle property of a button or link button to true, in which case the button will have two states—selected and deselected—and it will toggle between those states each time the user clicks it.

Radio buttons are quite different in use from standard buttons. Radio buttons are typically used in groups. Radio buttons can be selected or deselected, and only one button can be selected per group. For this reason, radio buttons are often used when you want to allow the user to select just one from a group of options. You should typically first create a RadioButtonGroup instance when using radio buttons. Then, assign the ID of the group to the groupName property of each radio button in the group, as shown here:

<mx:RadioButtonGroup id="exampleGroup" />
<mx:RadioButton groupName="exampleGroup" label="A" value="a" />
<mx:RadioButton groupName="exampleGroup" label="B" value="b" />

Checkboxes are also buttons. They are most similar to standard buttons that have been set to toggle. When a user clicks a checkbox, it toggles the selected state of the component (toggling the value of the selected property). The following creates a checkbox with a label of A and toggled to selected:

<mx:CheckBox id="exampleCheckbox" label="A" selected="true" />