ActionScript 3.0 Design Patterns.pdf - VideoTutorials-bg.com

Example 10-13. TestVid.as (continued)
}
}
flv_txt.text="Provide file name";
}
}
//Stop play
private function doStop (e:MouseEvent):void
{
vidTest.stopPlay (ns);
vid.clear ( );
}
Open a new Flash document file, and in the center of the stage, draw a rectangle
(W=320, H=240) with a 6-point stroke, the color value 9E0039, and the fill color
FAB383. Use the Align panel to make sure that the rectangle is perfectly centered
because it serves as a backdrop for the video that will be placed on top of it. In the
Document class window, type in TestVid, and test the application.
The UI is simple and related to the transitions—Stop and Start (playing video).You
can see the relationship between the video playing and the related trace statement
showing what happens when you press the button. For example, if you press Start
and the video is running, nothing new occurs because in the Play state, the
startPlay( ) function does nothing other than offering a trace statement to the effect
that you’re already playing.
Expanding the State Design: Adding States
A fundamental feature of virtually all design patterns is their ability to expand and
accept change. The kind of change you’re expecting in an application determines, to
some extent, the type of design pattern you select. In this particular application,
we’re adding states.
Adding the Pause State to the Statechart
The first state to be added to the state machine is a Pause state. This state only exists
inside the Play state, and you cannot get to the Pause state directly from the Stop state.
To get to the Pause state, you must first be in the Play state, and then you can turn the
Pause state on and off. To correctly depict this new state, we need to use a hierarchical
state diagram. Figure 10-5 shows a statechart with the necessary hierarchy.
The hierarchy in Figure 10-5 is a simple one. The first level is the Play and Stop
states, and then, within the Play state are the Pause and No Pause states.
Because the pause function is a toggle between the Play and Pause states, the No
Pause state is exactly the same as the Play state. So, rather than creating Pause Start
374 | Chapter 10: State Pattern