Flash MX 2004 Games : Art to ActionScript

Flash MX 2004 Games
Testing and debugging
If you have ‘Examples/Chapter01/pingpong03.fla’ open then you will see that there is a fourth
layer, labelled ‘Debug’. No developer ever gets it all right first time and when something doesn’t
work discovering where the errors are can be something of an art. One useful method is to send
information to a text box that you can see on screen. You can create a text box by choosing
the Text tool (the A icon) and then placing your mouse on the stage and typing in some text.
You can set the text box to operate as a Dynamic Text box using the Properties panel for the
Text tool.
Figure 1.17 Setting up a Dynamic Text box
In this example the settings are for a Multiline box that tracks the variable ‘debug’. Now if you
set the variable ‘debug’ to ‘Hello’ using ActionScript then that would appear in the box as the
program runs. We can use this tool to test lots of useful information about our program. We will
look into debugging in detail in Chapter 11.
The movement of the ball is a little more complicated than the movement of the bats. Open
‘Examples/Chapter01/pingpong04.fla’ and press ‘Ctrl + Enter’ to test it. Now the ball bounces
off the walls and the bats. Stop playing the game and try clicking the ball and selecting Actions.
Take a look at the code and see if you can work out what is going on. Don’t worry if you can’t,
this chapter is just a quick introduction and although the code in the ball isn’t too hard, it is much
more complicated than the script for the bats. By the time you have worked through the later
chapters of this book it will all be second nature.
Adding a scoreboard
One thing that we can do to improve the game is to add a score. Those strange boxes that both
have 123 in them will be where we put the score. The LeftBat scores every time the ball goes out
of screen right and the RightBat scores every time the ball goes out of screen left. So how do we
accomplish this?
Take a look at the section of code in the ball clip event that follows the comment ‘//Ball moving
right’. See how useful the comment is. Now you know that the ball is moving right in this section.
If it is moving right then the RightBat should hit it, if it doesn’t then the LeftBat scores a point.
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//Ball moving right
if (_x > 370){