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Advanced HitTest in Flash MX
Author: Art Bowles | Website: www.launchfire.com |

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Flash MX hitTest method

Usage

Movieclip.hitTest(x, y, shapeflag)
Movieclip.hitTest(target) Note on Usage
It got me confused in the beginning, so just to clarify, if you want to test if object A hits object B (ie does the rock hit the window) you have to write it as follows

If (window.hitTest(rock));

If performing a simple hit test with target, it will still work if written reversed, but it’s not correct.

Background

I wrote this tutorial after running into problems porting over one of my action games into
Flash MX. It seemed the hitTest function, at least how I had written it, was no longer valid. After some research I realized, MX does not accept eval on the left side of an argument, instead prefering to use brackets []. In fact, MX suggest any time you want to evaluate an expression, you place is inside []. To learn more read up on the symbol [] (array access) Eval (“A” + i); this[“A” + i]

Overview

My action game was a shoot the puck on the goalie/targets type game, in which I had to determine if the puck hit the target (easy) or the goalie (a little more difficult because of legs and arms). The target was a picture a circle inside a movie clip, and the goalie was basically the same. The trouble with the goalie was if it hit between his legs, that had to be a goal. So using the target argument was out, I needed to use x,y, and shapeflag arguments. In this tutorial, I am going to test using both target and shapeflag, mainly because I wanted to know what is possible in a variety of situations.

All the code for determining hits resides within the ActionPuck Movie Clip, on frame 6. Commented out are all the examples listed below.

Testing using the Target Argument

The ‘help’ file in MX says the target usually represents a button or text-entry field. Well, maybe, but I’ve only ever used it to reference another movie clip, so that’s what I’ll test against in this tutorial. On a basic level, testing for a hit using target is the same in MX or Flash 5, however, that’s about where the similarities end.

hit1 = _root.TestGoalie.hitTest("_root.ActionPuck"); //
F5 and MX compatible

if (hit1)
trace ("hit1");
if ( _root.TestGoalie.hitTest("_root.ActionPuck")) {
trace ("hit1");
}

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» Level Intermediate

Added: : 2003-01-14 Rating: 6.54 Votes: 28 Hits: 15

» Author

An ex network admin who found solace in lines of code.

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