You can convert an object to a symbol by using the F8 key.
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Answer:
of the power of Flash comes from its ability to create and manipulate symbols. A symbol is a master object that resides in one place—a panel called the Library—but can generate multiple copies of itself that can be used anywhere in Flash. Symbols offer a variety of advantages, including:
Economy. If you have a visible object that’s intended to appear more than once in a Flash movie, you can convert it to a symbol. You can then place any number of instances (copies) of that symbol on the stage without any significant increase in the movie’s file size.
Adaptability. Whenever you make a change in a symbol, that change is instantly reflected in all instances of the symbol.
Flexibility. Every symbol has its own internal timeline. As a result, a symbol can contain its own animated content that plays independently of the animation in the main timeline.
Nestability. Symbols can be embedded in other symbols, which can be embedded in still other symbols. By nesting symbols in this way, you can animate complex movements easily—for example, you could embed a symbol of a propeller turning inside a symbol of an airplane flying.
Scriptability. Two kinds of symbols—buttons and movie clips—can be controlled using ActionScript. Movie clips can even include scripts of their own, allowing them to control other movie clips or the movie that contains them.
This chapter shows you the basics of creating, modifying, and organizing symbols. More advanced use of symbols is covered in Chapter 5 (Creating Basic Animation) and Chapter 11 (Introducing ActionScript).
#22. Converting Objects to Symbols
Any object (or group of objects) that can appear on the stage can be made into a symbol. Here’s how to do it:
Select one or more objects on the stage. The selected objects may include paths, text objects, bitmaps, or even other symbols.
Choose Modify > Convert to Symbol, or press the F8 key. The Convert to Symbol dialog box appears.
(While this book usually doesn’t mention keyboard shortcuts, F8 is an exception because Convert to Symbol is such a frequently used command.)
Naming Symbols
Technically, Flash lets you assign to a symbol whatever name you like. In practice, however, there are two issues you may want to take into account when you name a symbol:
Convenience. Symbols listed in the library can be sorted by name or by type, but it’s much more convenient to have them sorted by name and by type without needing to switch between the two sorting modes. For this reason, many Flash developers like to give each symbol a prefix such as b_for button symbols, g_ for graphic symbols, and m_ for movie clip symbols.
Descriptiveness. The more precise your symbol names are, the easier it will be to find the one you want among dozens or hundreds of symbols. If your movie contains graphic symbols of a beagle, a poodle, and a schnauzer, don’t name the symbols g_dog1, g_dog2, and g_dog3. Instead, name them g_dogBeagle, g_dogPoodle, and g_dogSchnauzer.
Enter a name for the symbol into the Name field.
Click the radio button for the type of symbol you want to create: a movie clip, button, or graphic. (For the differences between these symbol types, see #27 and #28. If you’re experimenting with symbols for the first time, the simplest choice is Graphic.)
Click one of the small squares in the diagram next to the word Registration. The square you click will determine the symbol’s registration point (Figure 22a).
Figure 22a
Figure 22a Click the square corresponding to your preferred location for the symbol’s registration point. Later, when you view the symbol in the library or in symbol-editing mode, your registration point will be indicated by crosshairs.
Think of the registration point as the handle by which Flash will hold the symbol when it’s in motion (see #42). When you’re in doubt, the center is usually a good choice.
Group or Symbol?
Let’s say you have several objects on the stage that you want to make selectable with a single click. Should you group them, or convert them to a symbol? Here are some criteria to help you decide:
Impermanence. If you want just to bring the objects together temporarily, and you plan to separate them later, it’s quicker to use a group than a symbol.
Uniqueness. If a set of objects will appear only once in the movie, it’s more efficient to group them than to convert them to a symbol.
Movement. If you plan to animate a set of objects, convert them to a symbol. (As you’ll see in #42, both symbols and groups can be motion-tweened, but motion-tweening symbols is preferable.)