as3: check if an object is visibly blocked by another object - actionscript-3

I'm trying to check if an object is visibly "blocked" by another object at a certain xy spot. The normal hitTest method only states if two objects overlap or not, not which is visibly in front. Is there any way of achieving that, by having the xy-coordinates and two objects? So for example: 2 objects are on stage. Nr. 1 is in front and visibly covers Nr. 2 ... so an xy-hitTest with both objects should only return "true" for object nr. 1.
Thanks in advance :-)

The following function will use hitTestObject and the child indices of the objects to determine if obj1 is "in front of" obj2.
function isInFrontOf(obj1:DisplayObject, obj2:DisplayObject):Boolean{
return obj1.hitTestObject(obj2) && (obj1.parent.getChildIndex(obj1) > obj2.parent.getChildIndex(obj2));
}
Important note: This will only work if both objects have the same parent. You absolutely can rework the function to allow for different parents, but I'll leave that up to you.

Related

as3 hittestobject not working, dont understand why

the collision not working i cant understand why, i put collision movieclips in the object and it doesnt seem to recognise one of the but does with the other, sorry for the confusing way of stating the problem if you play the game you will understand. im open to changing the way collision works too as long as it works ill be super happy
I'll try to explain. When You click "Down" or "Up" hero (box_MC) collide with both doors "Top_Door" and "Bottom_Door". Inside "bang" function at first checking collision with "Bottom_Door", so, hero always go down (.y += 100) and second condition (Top_Door) never will be true. How to fix this? Add variable var lastAction:String;. This variable will store last action: "up" or "down". Inside "down_MC_P" function initialize this variable by "down". Inside "up_MC_P" — "up". Next, replace the first condition to this if (box_MC.hitTestObject(cycle[i].Bottom_Door) && lastAction == "down") and second: if(box_MC.hitTestObject(cycle[i].Top_Door) && lastAction == "up"). That's all.

AS3 Nullify Object through Reference

I have seem people asking this question, and getting an answer saying that this is impossible in AS3.
So I have a function called destroymc:
function destroymc(mcname:MovieClip):void{
mcname = null
}
This doesnot destroy the movieclip I want to destroy. Because it is passed by reference.
Is there really no way to make this work?
thanks.
Hm, as far as I know, to 'destroy' a MovieClip in AS3.0, you need to get rid of all references to it, and you need to remove it from the parent. Then the GC can collect it.
If you have an array of MovieClips, then something like this could work.
var mcs:Array;
// populate array
// to destroy the first one
mcs[0].parent.removeChild(mcs[0]); // remove the first element from its parent
mcs.shift(); // remove the first element in the array
And so if you want in in a function, you could pass the array to it
function destroymc(mcs:Array){
mcs[0].parent.removeChild(mcs[0]);
mcs.shift();
}
I'm using an array here because you need to use functions like this with dynamically generated MovieClips and entity managers and stuff. I hope this helps.

How do I HitTest two rotating objects properly? (A way to avoid bounding boxes)

I took an intro level flash course in college this semester and our final task was to make a mini-flash game.
I had to make a pipe-dream type game where there are a number of levels, and in each level you have to align the pipes so that the water flows and then you can pass to the next level.
I successfully made the first level, but upon making the second level,
where I placed a lot of curved pipes (by curved pipes I mean the attached image: ![Curved Pipe]: (http://imgur.com/mwpXAMn) )
I discovered that the method I use to decide when a level is complete is not working properly.
I was using HitTestObject, basically, I was testing whether 2 objects, Pipe_1, and Pipe_2, were intersecting. If all pipes intersected in the correct way, then procession to the next level is granted.
The problem with this I discovered is that flash has bounding boxes for movie clips you make, and that HitestObject uses bounding boxes to test for hits. Therefore, when you rotate a leftpipe so that it does not touch a straight pipe on screen, the bounding boxes still touch and it returns "collision" when in fact it is not actually touching on screen.
I looked up and found that you can use HitTestPoint but I can't figure out how to somehow make dynamic variables (that change upon rotation of object) that store one or two specific points on the leftpipe, say the two ends of it.
Once If I figure out how to get these values into a variable correctly, then I can figure out how to do HitTestpoint.
Also, I know of the LocaltoGlobal function but no matter what I try it keeps coming up with:
"Scene 1, Layer 'Layer 1', Frame 1, Line 30 1118: Implicit coercion of a value with static type Object to a possibly unrelated type flash.geom:Point."
meaning I don't know the correct code to store an x and a y coordinate as dynamic variables.
edit: ok since a person asked, I hunted this piece of code off the web and this is the one I was trying to play around with but to no avail:
How to use HitTest for 2 rectangles, r1 is rectangle 1 r2 is rectangle 2.
var r1width:Number = 135.0; //width of retangle 1 whith rotation 0
var r2width:Number = 93.0; //width of retangle 2 whith rotation 0
var p1:Object = {x:(r1width/2), y:(r1width/2)};
var p2:Object = {x:(-r1width/2), y:(r1width/2)};
var p3:Object = {x:(-r1width/2), y:(-r1width/2)};
var p4:Object = {x:(r1width/2), y:(-r1width/2)};
r1.localToGlobal(p1);
r1.localToGlobal(p2);
r1.localToGlobal(p3);
r1.localToGlobal(p4);
var p5:Object = {x:(r2width/2), y:(r2width/2)};
var p6:Object = {x:(-r2width/2), y:(r2width/2)};
var p7:Object = {x:(-r2width/2), y:(-r2width/2)};
var p8:Object = {x:(r2width/2), y:(-r2width/2)};
r2.localToGlobal(p5);
r2.localToGlobal(p6);
r2.localToGlobal(p7);
r2.localToGlobal(p8);
if((r2.hitTest(p1.x, p1.y, true))||(r2.hitTest(p2.x, p2.y, true))||(r2.hitTest(p3.x,
p3.y, true))||(r2.hitTest(p4.x, p4.y, true)))
{
trace('collision');
}
if((r1.hitTest(p5.x, p5.y, true))||(r1.hitTest(p6.x, p6.y, true))||(r1.hitTest(p7.x,
p7.y, true))||(r1.hitTest(p8.x, p8.y, true)))
{
trace('collision');
}
I did not write this code and it does not work. I'm not sure what "Object" is because I've never used it before, I'm assuming in this case it's sort of acting like a coordinate pair.
Also, this code is to hittest 2 rectangles, whereas I'm using an L-shaped pipe, so the x/y calculation would be quite different I imagine.
This code above gives the same error that I posted before:
Implicit coercion of a value with static type Object to a possibly unrelated type flash.geom:Point.
and it gives it first on line r1.localToGlobal(p1);
Instead of using Object, you need to use Point like so:
var p1:Point = new Point(r1width/2, r1width/2);

AS3 Using Many Event Listeners Causing Problems, How to Reduce?

Confusing title, my bad.
Basically, I have a list of names. Looping through, I add a MovieClip, Set 2 properties to it, the name, and an ID. The MovieClip is at the same time made to function as a button and I add 4 listeners, mouse up, over, down, or out. I do this with every name. The function each one is set to is the same.
EX: enemyButton[i].addEventListener(MouseEvent.MOUSE_UP, mouseUpHandler);
The enemyID turns up "not valid property," time to time when I click, it doesn't crash at all, but sometimes I have to hit the button a few times.
I have narrowed the problem down to having to be caused by the listeners.
The function as simple as:
EX: function mouseUpHandler(e:MouseEvent):void { enemySelected(e.target.enemyID); }
My question is, is too many listeners likely to be the problem? and how can I reduce them?
Here's a snippet of the loop:
var C:Class = Class(getDefinitionByName(enemies[i]));
var c:* = new C();
c.gotoAndStop(1);
enemyButton[i].enemyID = i;
c.name = "select" + i;
c.enemyID = i;
trace(c.enemyID);
enemyButton[i].addChild(c);
enemyScroll.addChild(enemyButton[i]);
enemyButton[i].enemyName.text = info[i][Const.NAME];
enemyButton[i].setChildIndex(enemyButton[i].getChildByName("enemyName"), enemyButton[i].numChildren-1);
Thanks.
If enemyButton is a MovieClip (created via attachMovie, maybe) and not strongly typed as a EnemyButton class, then the ID property becomes dynamic. In this situation, if your list of names contains incorrect data (missing ID field, maybe), then the ID property will remain undefined on some instances of the MovieClip.
You can check the list of data used to generate movie clips. You can run into the same error if you have blank lines in your data.
This has nothing to do with event listeners.
So you just want to generate a bunch of buttons with unique properties and know what button was clicked last. Generally it is very bad idea to implement button logic outside button object. Why? Because you work with object oriented language. Good news is that you work with as3 and it treats functions as objects, so you can assign function to var like this:
var callback:Function = function(name:String, enemyId:int){ /*do something*/ }
And.. you can pass function as a parameter to another function
function setCalback(func:Function){}
button.setCallback(callback);
So, what you really need is to create your own button class, add listeners inside it, add handlers(static handlers will reduce memory usage) and pass callback function to it, that will be called when user clicks button.
Don't mean to spam this much but this was easily fixed, though the responses might have been a better method.
I just had to change target to the currentTarget, that then allowed clicking anywhere on the "button" to work. Whereas before the target varied from childs added to it.
So, solved.
Thanks for the help.

retrieving a variable value from lower level

well i created some variables in the main stage level, with something like this:
for(i=0,i<10,i++){
var var_name="var_num_"+i;
this[var_name]="some value";
}//<-----------------------------------------------------works
so i get 10 variables named "var_num0", "var_num1", "var_num2" each one with some value.
and i can acces them any where calling this
var second_var=MovieClip(root).var_num0;//<--------------works
my problem comes when i want to call all the variables from a lower level or in another frame or somewhere else using another loop:
var third_var;
for(j=0,j<3,j++){
third_var=this["MovieClip(root).var_num_"+j];//<---------DOSNT WORK
trace(this["MovieClip(root).var_num_"+j]);//<------------returns "undefined"
}
how can i make this work? i tried a lot of things and nothing...
thanks you all
In your case both "root" and "this" are the scope you want to access the vars from. so try this:
var third_var:MovieClip;
for(j = 0; j < 3; j++)
{
third_var = MovieClip(root)[var_num_ + j];
trace(third_var);
}
Also you should have semi-colons in your for loop rather than comers.
I'd like to preface my answer with a suggestion you use a 'Document Class' with AS3 to make things like namespaces and inheritance much clearer. You know exactly where things are accessible when using document based, object oriented programming versus the timeline programming available through the Flash IDE (its only there because of AS1/2). Tut: http://www.kirupa.com/forum/showthread.php?223798-ActionScript-3-Tip-of-the-Day/page14
On to the answer: You are trying to move two levels of inheritance in one set of [] Another way of writing your first "Doesn't work" line is:
this.myMovieClip["var_num"+j"];
You could also use: this["MovieClip"]["var_num"+j];
Basically, you need to take the "MovieClip(root)" out of the string you are using to call your variable because you are passing through two levels of inheritance: this->MovieClip->targetVar
You need to use two periods, a period and a set square bracket or two sets square brackets to move two levels of inheritance. A period . and a set of square brackets [] both accomplish the task of moving one level deeper, so putting the . inside the string used to call up your variable won't work.
Explanation:
The following three examples all return the same variable:
myMovieClip.my_variable
myMovieClip["my_variable"]
var str:String = "my_variable";
myMovieClip[str];