Actionscript 3.0 - Custom Events with Parameters

问题

Is there any simple -- or suggested -- way in order to send a parameter along with a custom event? Or even just a way to pass variables between two classes?

My program is a sort of simple Civ/Age of Empires kind of game, where you can place buildings on tiles. This would work as follows:

Player clicks on the icon on the HUD, which creates an dispatches an event which is received by the PLAYER class.
The PLAYER class changes a value depending on which building is held (clicked on).
Player clicks on the tile in the grid to place it, which dispatches an event which is received by the PLAYER class.
The PLAYER class creates a building object and adds it to an array within the PLAYER class.

An example of how I'd want the code to work:

icon.as

private function onMouseClick(e:MouseEvent = null):void {
        var iconClickedEvent:Event = new Event("BUILDING_HELD", buildingType);  // passes "buildingType" through the event somehow
        stage.dispatchEvent(iconClickedEvent);
}

tile.as

private function onMouseClick(e:MouseEvent = null):void {
        var buildingPlacedEvent:Event = new Event("BUILDING_PLACED", xRef, yRef);// passes "xRef" & "yRef", the tile's co-ordinate
        stage.dispatchEvent(buildingPlacedEvent);
}

player.as

private function init(e:Event):void {
        stage.addEventListener("BUILDING_HELD", buildingHeld(buildingType));
        stage.addEventListener("BUILDING_PLACED", placeBuilding(xRef, yRef));
}

private function buildingHeld(building:int):void {
        buildingType = building;
}

private function placeBuilding(xRef:int, yRef:int):void {
        switch(buildingType){
                case 1: // main base
                        MainBaseArray.push();
                        MainBaseArray[length-1] = new MainBase(xPos, yPos);     // create new object with the references passed
                        break;
        }
}

回答1:

The best way to manage this is to create custom event classes for each of your events (or event types). If you create a class that inherit Event, it will be usable in the same ways that a standard Event, but can contain custom values or methods.

Here's an example of such class :

public class BuildingEvent extends Event {

  // contains an event name. Usefull to ensure at compile-time that there is no mistape in the event name.
  public static const BUILDING_HELD:String = "BUILDING_HELD";

  private var _buildingType:int;

  // the constructor, note the new parameter "buildingType". "bubbles" and "cancelable" are standard parameters for Event, so I kept them. 
  public function BuildingEvent(type:String, buildingType:int, bubbles:Boolean = false, cancelable:Boolean = false) {
    super(type, bubbles, cancelable);
    _buildingType = buildingType;
  }

  // using a getter ensure that a listening method cannot edit the value of buildingType.
  public function get buildingType() {
    return _buildingType;
  }
}

We can then use this class like this :

// to dispatch the event
private function onMouseClick(e:MouseEvent = null):void {
  var iconClickedEvent:BuildingEvent = new BuildingEvent(BuildingEvent.BUILDING_HELD, buildingType);
  stage.dispatchEvent(iconClickedEvent);
}

// to listen to the event
private function init(e:Event):void {
  stage.addEventListener(BuildingEvent.BUILDING_HELD, buildingHeld);
}
private function buildingHeld(event:BuildingEvent):void {
  buildingType = event.buildingType;
}

来源：https://stackoverflow.com/questions/23557297/actionscript-3-0-custom-events-with-parameters

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actionscript-3

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variables

custom-events