Flash AS3教程：教你用代码创建好看的遮罩动画效果

package {
import flash.display.MovieClip;
public class MyMask extends MovieClip {
//Mask’s x and y speed
public var speedX:Number;
public var speedY:Number;
//Set the given scale for this mask, when we create a new
//mask object
public function MyMask(scale:Number) {
this.scaleX = scale;
this.scaleY = scale;
}
}
}

//We use an array to hold all our masks.
//(Except the mask that follows our cursor)
var masks:Array = new Array();
//We add all of the masks to a container
var maskContainer:Sprite = new Sprite();
//Set the maskContainer to be the image’s mask
backgroundImage.mask = maskContainer;
//Add the container on the stage
addChild(maskContainer);
//Create the mask which follows cursor movement (master mask)
var masterMask:MyMask = new MyMask(1);
//Set the master masks’s coordinates to match cursor’s coordinates
masterMask.x = mouseX;
masterMask.y = mouseY;
//Add the master mask to a container
maskContainer.addChild(masterMask);
//Cache the image and container as bitmap, so we
//can animate the alpha of the masks
maskContainer.cacheAsBitmap=true;
backgroundImage.cacheAsBitmap=true;
//Create a timer that is called every 0.2 seconds
var timer:Timer = new Timer(200,0);
timer.addEventListener(TimerEvent.TIMER, timerEvent);
timer.start();
//This function is called every 0.2 seconds.
//We create a new mask in this function.
function timerEvent(e:TimerEvent):void {
//Calculate a random scale for the new mask (0 to 1.5)
var scale:Number = Math.random() * 1.5 + 0.5;
//Create a new mask with random scale
var newMask:MyMask = new MyMask(scale);
//Set the position for the new mask
newMask.x = mouseX;
newMask.y = mouseY;
//Assign a random x and y speed for the mask
newMask.speedX = Math.random() * 20 - 10;
newMask.speedY = Math.random() * 20 - 10;
//Add the mask to the container
maskContainer.addChild(newMask);
//Add the mask to the array
masks.push(newMask);
}
//We need ENTER_FRAME to animate the masks
addEventListener(Event.ENTER_FRAME, enterFrameHandler);
//This function is called in each frame
function enterFrameHandler(e:Event):void {
//Loop through the mask array
for (var i:uint = 0; i < masks.length; i++) {
//Save a mask to a local variable
var myMask:MyMask = (MyMask)(masks[i]);
//Update the x and y position
myMask.x += myMask.speedX;
myMask.y += myMask.speedY;
//Increase the scale
myMask.scaleX += 0.1;
myMask.scaleY += 0.1;
//Reduce the alpha
myMask.alpha -= 0.01;
//If the alpha is below 0, remove the mask
//from the container and from the array
if (myMask.alpha < 0) {
masks.splice(i,1);
maskContainer.removeChild(myMask);
}
}
//Update the master mask position
masterMask.x = mouseX;
masterMask.y = mouseY;
}

//We need these classes for the animation
import fl.transitions.Tween;
import fl.transitions.easing.*;

//These are the mask rectangle’s width and height
var boxWidth:Number = 40;
var boxHeight:Number = 40;

//We want nine rows and 14 columns to make the animation look nice
var rows:Number = 9;
var columns:Number = 14;

//We will add the rectangle’s into an array (we need this array in the animation)
var rectangles:Array = new Array();

//We add the tweens into an array so they don’t get carbage collected
var tweens:Array = new Array();

//This container will hold all the mask rectangles
var container:Sprite = new Sprite();

//Add the container onto the stage
addChild(container);

//Set the container to be the image’s mask
cityMC.mask = container;

//Loop through the rows
for (var i=0; i < rows; i++) {

//Loop through the columns
for (var j=0; j < columns; j++) {

//Create a new mask rectangle
var maskRectangle:MaskRectangle = new MaskRectangle();

//Position the mask rectangle
maskRectangle.x = j * boxWidth;
maskRectangle.y = i * boxWidth;

//Set the scaleX to be 0, so the rectangle will not be visible
maskRectangle.scaleX = 0;

//Add the rectangle onto the container
container.addChild(maskRectangle);

//Add the mask rectangle to the rectangles array
rectangles.push(maskRectangle);
}
}

//Create and start a timer.
//This timer is called as many times as there are rectangles on the stage.
var timer = new Timer(35,rectangles.length);
timer.addEventListener(TimerEvent.TIMER, animateMask);
timer.start();

//This function is called every 0.035 seconds
function animateMask(e:Event):void {

//Save the rectangle to a local variable
var rectangle = rectangles[timer.currentCount - 1];

//Tween the scaleX of the rectangle
var scaleTween:Tween = new Tween(rectangle,"scaleX",Regular.easeOut,0,1,1,true);
tweens.push(scaleTween);

}

//This container contains all the mask graphics
var container:Sprite = new Sprite();
addChild (container);

//Set the container to be the image’s mask
imageMC.mask = container;

//Set the starting point
container.graphics.moveTo (mouseX, mouseY);
addEventListener (Event.ENTER_FRAME, enterFrameHandler);
/*Draw a new rectangle in each frame and add it onto the container
NOTE: you can use all kinds of shapes, not just rectangles! */
function enterFrameHandler (e:Event):void {
container.graphics.beginFill(0xff00ff);
container.graphics.drawRect(mouseX-50, mouseY-50, 100, 100);
container.graphics.endFill();
}
Mouse.hide();