MACROMEDIA FLASH 8-DEVELOPING FLASH LITE 2.X User Manual download pdf (Page 18)

Adobe Flash CS3 Classroom in a Book

Lesson 10 revisits the preloader graphic students

created in Lesson 2 as students learn how to script the

preloader and load a separate SWF ﬁle.

Working with preloaders

Preloaders entertain viewers and keep them informed

while the primary content of a website is loading.

Because website visitors are easily distracted and may

click away from a site if nothing seems to be happen-

ing, many complex sites use preloaders. A preloader

may be as simple as a progress bar, or it may be related

to the content that is loading. Ask students to think of

preloaders they’ve seen or preloaders they might use

for different kinds of sites. (To ﬁnd examples, try visit-

ing the sites of graphic designers or sites that feature

movie ﬁles.)

Previewing a preloader

A preloader only plays until the main content has

loaded, so if you’re running it on the computer that

contains the content, the preloader will disappear

quickly. To see what viewers will actually see, simulate a

download.

In simulating the downloading speed, Flash uses esti-

mates of typical Internet performance, not the exact

modem speed. For example, if you select to simulate a

modem speed of 28.8 Kbps, Flash sets the actual rate to

2.3 Kbps to reﬂect typical Internet performance. The

proﬁler also compensates for the added compression

support for SWF ﬁles, which reduces the ﬁle size and

improves streaming performance.

To test a movie:

1. Choose Control > Test Movie.

2. In the preview window, choose View > Download

Settings.

3. Select a download speed to determine the streaming

rate that Flash simulates. When viewing the SWF ﬁle,

choose View > Bandwidth Proﬁler to see a graph of the

downloading performance.

• The left side of the proﬁler displays information

about the document, its settings, its state, and streams,

if any are included in the document.

• The right section of the proﬁler shows the Timeline

header and graph. In the graph, each bar represents an

individual frame of the document. The size of the bar

corresponds to that frame’s size in bytes. The red line

beneath the Timeline header indicates whether a given

frame streams in real time with the current modem

speed set in the Control menu. If a bar extends above

the red line, the document must wait for that frame to

load.

4 Choose View > Simulate Download to turn stream-

ing off or on. If you turn streaming on, the document

starts over and simulates a web connection.

Optimizing Flash documents

As your document ﬁle size increases, so does its down-

load time and playback speed. You can take several

steps to prepare your document for optimal playback.

As part of the publishing process, Flash automatically

performs some optimization on documents. Before

exporting a document, you can optimize it further by

using various strategies to reduce the ﬁle size. You can

also compress a SWF ﬁle as you publish it. As you make

changes, test your document by running it on a variety

of computers, operating systems, and Internet connec-

tions.

• Use symbols, animated or otherwise, for every ele-

ment that appears more than once.

• Use tweened animations whenever possible when

creating animation sequences. Tweened animations use

less ﬁle space than a series of keyframes.

• Use movie clips instead of graphic symbols for anima-

tion sequences.

• Limit the area of change in each keyframe; make the

action take place in as small an area as possible.

• Avoid animating bitmap elements; use bitmap images

as background or static elements.

• Use mp3, the smallest sound format, whenever pos-

sible.

• Group elements.

Lesson 10: Loading and Optimizing

Flash Content

LESSON 10

1 2 ... 13 14 15 16 17 18 19 20 21

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