Actionscript 3 drag and drop on multiple specific targes and change alpa for the dropped objects as well as stack targets - actionscript-3

Question

I have been trying to achieve three things in the project without success. I am new at this and have relied on tutorials to get this far. Here we go!!
a. I want to be able to drop label_3 and label_4 on either or targetlabel_3 and targetlabel_4 but not effect the other labels and targets.
b. I want to be able to drop label_2 on top of label_1 once it has been dropped. I am finding that when label_1 has been dropped, it hides the targetlabel_2 and label_2 can't find it's target.
c. I want to change the Alpa of each of labels _1, _2, _3, _4 and _5 to zero when they are dropped on their targets and change the Apha for labels _11, _21, _31, _41 and _51 to 100. (I have changed the Apha to 25 on these for the sake of making it easier for someone to see what I am trying to do).
I have been mucking around for days on this and have hit a brick wall.
Can anyone help please?
import flash.display.DisplayObject;
import flash.geom.Rectangle;
/* Drag and Drop
Makes the specified symbol instance moveable with drag and drop.
*/
var startX:Number;
var startY:Number;
var counter = 0;
var attempts = 0;
var rect:Rectangle;
rect=new Rectangle(100,100,700,500);
correct_txt.text=counter;
attempts_txt.text=attempts;
label_1.addEventListener(MouseEvent.MOUSE_DOWN,Drag);
label_1.addEventListener(MouseEvent.MOUSE_UP,Drop);
label_2.addEventListener(MouseEvent.MOUSE_DOWN,Drag);
label_2.addEventListener(MouseEvent.MOUSE_UP,Drop);
label_3.addEventListener(MouseEvent.MOUSE_DOWN,Drag);
label_3.addEventListener(MouseEvent.MOUSE_UP,Drop);
label_4.addEventListener(MouseEvent.MOUSE_DOWN,Drag);
label_4.addEventListener(MouseEvent.MOUSE_UP,Drop);
label_5.addEventListener(MouseEvent.MOUSE_DOWN,Drag);
label_5.addEventListener(MouseEvent.MOUSE_UP,Drop);
label_1.buttonMode = true;
label_2.buttonMode = true;
label_3.buttonMode = true;
label_4.buttonMode = true;
label_5.buttonMode = true;
function Drag(event:MouseEvent):void
{
event.target.startDrag(true,rect);
feedback_txt.text="";
event.target.parent.addChild(event.target);
startX=event.target.x;
startY=event.target.y;
}
function Drop(event:MouseEvent):void
{
event.target.stopDrag();
var myTargetName:String="target" + event.target.name;
var myTarget:DisplayObject=getChildByName(myTargetName);
if (event.target.dropTarget!=null&&event.target.dropTarget.parent==myTarget){
feedback_txt.text="Well done! You have selcted the correct label and placed it in the recommended position on the package.";
feedback_txt.textColor = 0xCC0000
event.target.removeEventListener(MouseEvent.MOUSE_UP,Drop);
event.target.removeEventListener(MouseEvent.MOUSE_DOWN,Drag);
event.target.buttonMode = false;
event.target.x=myTarget.x;
event.target.y=myTarget.y;
counter++;
correct_txt.text=counter;
correct_txt.textColor = 0x0000ff
attempts++;
attempts_txt.text=attempts;
attempts_txt.textColor = 0x0000ff
}else{
feedback_txt.text="Your attempt is not quite correct. You have either selected the incorrect label or placed it in the wrong position. Please try again.";
event.target.x = startX;
event.target.y = startY;
attempts++;
attempts_txt.text = attempts;
}
if (counter==5){
feedback_txt.text="Well done! You have correctly placed all 5 labels";
percentage_txt.text ="Based on your attempts, you have scored "+Math.round ((counter/attempts) *100)+" %";
percentage_txt.textColor = 0x0000ff
}
}

Answer 1

The easiest way to detect when a label is on another label is by using hittest in an enter frame event listener.
stage.addEventListener(Event.ENTER_FRAME, hit_test);
function hit_test(e:Event):void{
if (label_1.hitTestObject(targetLabel_1)) {
trace("Label_1 is hitting targetlabel_1");
label_hit();
}
if (label_2.hitTestObject(targetLabel_2)) {
trace("Label_2 is hitting targetlabel_2");
label_hit();
}
}
When the hittest is activated, the trace text is shown and the function is called. To change the alphas of the labels, use the function being called by the hittest. For example:
function label_hit()
{
label_1.alpha = 0;
label_2.alpha = 0;
label_3.alpha = 0;
}
If you are trying to have conditions to when things can be dragged, seen, or hit tested, that function is also where you can take care of them. For example, If you don't want a label to be visible until the hittest, you have the alpha set to 0 until the function sets it to 100. If you don't want a label to be drageable until then, you create the listener inside the function instead of earlier.
function label_hit()
{
label_1.alpha = 100;
label_1.addEventListener(MouseEvent.MOUSE_DOWN,Drag);
label_1.addEventListener(MouseEvent.MOUSE_UP,Drop);
}
If you want hittests to occur only after other hittests have already occured, place them in conditions and have the conditions met in the functions.
stage.addEventListener(Event.ENTER_FRAME, hit_test);
function hit_test(e:Event):void{
if (label_1.hitTestObject(targetLabel_1)) {
trace("Label_1 is hitting targetlabel_1");
label_hit();
}
if(condition)
{
if (label_2.hitTestObject(targetLabel_2)) {
trace("Label_2 is hitting targetlabel_2");
label_hit();
}
}
function label_hit()
{
var condition = true;
}