Flash glossary: Button symbol

Button symbols are a special type of four-frame interactive movie clip in Adobe Flash Professional. When you select the button type when creating a symbol, Flash creates a Timeline with four frames. The first three frames display the button's three possible states: Up, Over, and Down; the fourth frame defines the active area of the button. The button symbol timeline doesn't actually play linearly like a normal timeline; it reacts to mouse pointer movement and actions by jumping to the appropriate frame.

To make a button interactive, place an instance of the button symbol on the Stage and assign actions to the instance. You assign the actions to the root timeline of the Flash file. If the button is inside a movie clip, you can add the actions to the movie clip's timeline. Do not add actions to the timeline of the button symbol.

Each frame in the Timeline of a button symbol has a specific function:

• Frame 1 is the Up state, representing the button whenever the user's cursor is not over the button
• Frame 2 is the Over state, representing the button's appearance when the pointer is over the button
• Frame 3 is the Down state, representing the button's appearance as it is clicked
• Frame 4 is the Hit state, defining the physical area of influence that responds to the mouse click (this area is invisible when the SWF file plays in Flash Player)

To create a button symbol, follow these steps:

1. Choose Insert > New Symbol or press Control+F8 (Windows) or Command+F8 (Mac).
2. In the Create New Symbol dialog box, enter a name for the new button symbol. Choose Button as the symbol type. Flash switches to symbol-editing mode. The Timeline changes to display four consecutive frames. The frames are labeled Up, Over, Down, and Hit. The first frame, Up, contains a blank keyframe.
   
3. To create the Up state button image, select the Up frame in the Timeline and then use the drawing tools, import a graphic, or place an instance of another symbol on the Stage. You can use graphic symbols or movie clip symbols inside a button, but you cannot use another button symbol.
   
4. In the Timeline, click the Over frame, and then choose Insert > Timeline > Keyframe. Flash inserts a keyframe that duplicates the contents of the preceding Up frame.
   
5. With the Over frame still selected, change or edit the button image on the Stage to create the desired appearance for the Over state.
6. Repeat Steps 4–5 to edit the Down frame and the Hit frame.

Editing the Hit frame is optional. The contents of the Hit frame are not visible on the Stage during playback, but the graphics you add to it define the physical area of the button that responds when clicked. This is useful when the graphic elements of the button are different sizes or unsymmetrical, which can make the button harder for a user to click.

To learn more about button symbols, see the section titled Creating buttons in the Flash documentation.