AS3 CookBook学习整理(十)
1. 在指定方向(角度)上移动
x方向的增量取的是Math.cos(angle)，y方向的增量取的是Math.sin(angle)
package {
import flash.display.Sprite;
import flash.events.TimerEvent;
import flash.utils.Timer;
public class Sample0514 extends Sprite
{
private var circle:Sprite;
private var angle:Number = 45;
private var speed:int = 6; //速度为每帧6像素
public function Sample0514()
{
circle = new Sprite();
circle.graphics.beginFill(0xFFFF00);
circle.graphics.drawCircle(50,50,30);
circle.graphics.endFill();
this.addChild(circle);
var timer:Timer = new Timer(30);
timer.addEventListener(TimerEvent.TIMER,onTimer);
timer.start();
}
private function onTimer(event:TimerEvent):void
{
var radian:Number = angle * Math.PI / 180;
circle.x += Math.cos(radian) * speed;
circle.y += Math.sin(radian) * speed;
}
}
}2. 减速运动
x方向的移动：(mouseX - object.x) * speed;
y方向的移动：(mouseY - object.y) * speed;
物体与目标位置的距离：
var vx:Number = (mouseX - circle.x);
var vy:Number = (mouseY - circle.y);
var distance:Number = Math.sqrt(vx*vx + vy*vy);
package {
import flash.display.Sprite;
import flash.events.MouseEvent;
import flash.events.TimerEvent;
import flash.utils.Timer;
public class Sample0515 extends Sprite
{
private var timer:Timer;
private var circle:Sprite;
public function Sample0515()
{
circle = new Sprite();
circle.graphics.beginFill(0xFFFF00);
circle.graphics.drawCircle(0,0,25);
circle.graphics.endFill();
this.addChild(circle);
stage.addEventListener(MouseEvent.CLICK,onClick);
timer = new Timer(30);
timer.addEventListener(TimerEvent.TIMER,onTimer);
timer.start();
}
private function onClick(event:MouseEvent):void
{
if(circle.x != mouseX && circle.y != mouseY)
{
timer.start();
}
}
private function onTimer(event:TimerEvent):void
{
var vx:Number = (mouseX - circle.x);
var vy:Number = (mouseY - circle.y);
var distance:Number = Math.sqrt(vx*vx + vy*vy);
if(distance<1)
{
timer.stop();
circle.x = mouseX;
circle.y = mouseY;
}
else
{
circle.x += vx * 0.1;
circle.y += vy * 0.1;
}
}
}
}3. 加速运动
加速运动，就是每次移动时，坐标的增量递增
package {
import flash.display.Sprite;
import flash.events.Event;
public class Sample0526 extends Sprite
{
private var circle:Sprite;
private var speed:Number = 0.5;
private var angle:Number = 45;
public function Sample0526()
{
circle = new Sprite();
circle.graphics.beginFill(0xFFFF00);
circle.graphics.drawCircle(50,50,20);
circle.graphics.endFill();
this.addChild(circle);
this.addEventListener(Event.ENTER_FRAME,onEnterFrame);
}
private function onEnterFrame(event:Event):void
{
var radian:Number = angle * Math.PI /180;
speed += .3;
circle.x += Math.cos(radian) * speed;
circle.y += Math.sin(radian) * speed;
}
}
}4. 弹簧(胡克定律)
胡克的弹性定律指出：在弹性限度内，弹簧的弹力f和弹簧的长度x成正比，即f= -kx。k是物质的弹性系数，它由材料的性质所决定，负号表示弹簧所产生的弹力与其伸长（或压缩）的方向相反。
F=k·x
F -- 表示弹簧的弹力，单位是牛
k -- 劲度系数，单位是牛/米
x -- 是弹簧伸长或缩短的长度，单位是米
as实现弹簧定律的关键代码：
<1> 设定一个目标点(x1,y1)
<2> 得到物体中心点(x,y)到目标点(x1,y1)的增量(拉伸量，对应胡克定律里的x)
<3> 将增量累加到变量保存(vx,vy)
<4> 物体每次增加vx,vy(vx,vy为正值，则为远离中心点的弹簧动作；为负值，则为接近中心点的弹簧动作)
<5> 加上损耗(_vx *= 0.95; _vy * 0.95)，不加损耗则为永动，类似钟摆效果。
一般在as里，设置k(劲度系数)为0.1或0.2；损耗设置为0.95(每次弹跳丢失5%的能量)
package {
import flash.display.Sprite;
import flash.events.Event;
import flash.events.MouseEvent;
public class Sample0601 extends Sprite
{
private var circle:Sprite;
private var vx:Number = 0;
private var vy:Number = 0;
private var flag:Boolean = false;
private var targetX:Number;
private var targetY:Number;
public function Sample0601()
{
circle = new Sprite();
circle.graphics.beginFill(0xFFFF00);
circle.graphics.drawCircle(0,0,30);
circle.graphics.endFill();
circle.x = circle.y = 100;
this.addChild(circle);
stage.addEventListener(MouseEvent.CLICK,onClick);
stage.addEventListener(Event.ENTER_FRAME,onEnterFrame);
}
private function onEnterFrame(event:Event):void
{
if(flag)
{
var ax:Number = (targetX - circle.x) * .1;
var ay:Number = (targetY - circle.y) * .1;
vx += ax;
vy += ay;
circle.x += vx;
circle.y += vy;
vx *= .95;
vy *= .95;
}
}
private function onClick(event:MouseEvent):void
{
flag = true;
targetX = mouseX;
targetY = mouseY;
}
}
}5. 利用sin和cos实现旋转，循环运动或摆动
Math.sin()和Math.cos函数的返回值范围在 -1 到 1 之间，sin()是从小到大，cos()是从大到小
可以通过循环输出sin()或cos()来得到一个范围内的一串数字，例如：
for(var i:Numer = 0; i<10; i+= 0.1)
{
trace(Math.sin(i)*50);//将输出-50到50之间的数字
trace(Math.cos(i)*50);//将输出50到-50之间的数字
}根据上面的规律，可以实现左右摆动(钟摆)、沿中心点转动的效果
package {
import flash.display.Sprite;
import flash.events.Event;
public class Sample0601 extends Sprite
{
private var circle:Sprite;
private var angle:Number = 0;
public function Sample0601()
{
circle = new Sprite();
circle.graphics.beginFill(0xFFFF00);
circle.graphics.drawCircle(0,0,20);
circle.graphics.endFill();
this.addChild(circle);
this.addEventListener(Event.ENTER_FRAME,onEnterFrame);
}
private function onEnterFrame(event:Event):void
{
//左右摆动
//circle.x = 200 + Math.sin(angle) * 50;
//逆时针沿着中心点做圆周运动
circle.x = 200 + Math.sin(angle) * 50;
circle.y = 200 + Math.cos(angle) * 50;
//顺时针沿着中心点做圆周运动
//circle.x = 200 + Math.cos(angle) * 50;
//circle.y = 200 + Math.sin(angle) * 50;
//逆时针沿着中心点做椭圆形运动
//circle.x = 200 + Math.sin(angle) * 50;
//circle.y = 200 + Math.cos(angle) * 20;
//随机运动
//circle.x = 200 + Math.sin(xAngle) * xRadius;
//circle.y = 200 + Math.cos(yAngle) * yRadius;
//_xAngle += _xSpeed;
//_yAngle += _ySpeed;
angle += .2;
}
}
}6. 利用Math.atan2(y, x)计算两个点的夹角
已知一个点(x1, y1)，通过Math.atan2(y1, x1)可以得到这个点相对于坐标原点(0, 0)X轴的夹角
假如有两个点A(x1, y1)、B(x2, y2)，则可以将A点视为坐标原点(0, 0)，然后通过Math.atan2(y2 - y1, x2 - x1)计算出A、B两点的夹角
一个眼珠跟随鼠标效果：
package {
import flash.display.Sprite;
import flash.events.Event;
public class Sample0601 extends Sprite
{
private var circle:Sprite;
private var angle:Number = 0;
public function Sample0601()
{
circle = new Sprite();
circle.graphics.beginFill(0xFFFFFF);
circle.graphics.drawCircle(0,0,30);
circle.graphics.endFill();
circle.graphics.beginFill(0x000000);
circle.graphics.drawCircle(20,0,5);
circle.graphics.endFill();
circle.x = circle.y = 200;
this.addChild(circle);
this.addEventListener(Event.ENTER_FRAME,onEnterFrame);
}
private function onEnterFrame(event:Event):void
{
var dx:Number = mouseX - circle.x;
var dy:Number = mouseY - circle.y;
var radian:Number = Math.atan2(dy,dx);
circle.rotation = radian * 180 / Math.PI;
}
}
}7. 弹簧(胡克定律)用来实现缩放(忽大忽小)
胡克定律也可以应用在缩放值(scale)上，生成一种匀速的缩放，一种应用是心脏扑通扑通跳动效果
package {
import flash.display.Sprite;
import flash.events.Event;
import flash.events.MouseEvent;
public class Sample0602 extends Sprite
{
private var rect:Sprite;
private var vx:Number = 0;
private var randomNum:Number = 1;
public function Sample0602()
{
rect = new Sprite();
rect.graphics.beginFill(0xFFFF00);
rect.graphics.drawRect(-50,-50,100,100);
rect.graphics.endFill();
rect.x = 200;
rect.y = 150;
this.addChild(rect);
rect.addEventListener(MouseEvent.CLICK,onClick);
this.addEventListener(Event.ENTER_FRAME,onEnterFrame);
}
private function onClick(event:MouseEvent):void
{
randomNum = Math.random() * 2 - 0.5;
}
private function onEnterFrame(event:Event):void
{
vx += (randomNum - rect.scaleX) * 0.1;
rect.scaleX += vx;
rect.scaleY = rect.scaleX;
vx *= .9;
}
}
}8. 从一种颜色匀速变化到另一种颜色
利用物体的ColorTransform属性，改变redMultiplier, greenMultiplier, blueMultiplier的值
例如：newRed = (改变颜色的redMultiplier值 - 现在的redMultiplier值) * speed;
package {
import flash.display.Sprite;
import flash.events.Event;
import flash.events.MouseEvent;
import flash.geom.ColorTransform;
public class Sample0602 extends Sprite
{
private var _sprite:Sprite;
private var _red2:Number = 0;
private var _green2:Number = 0;
private var _blue2:Number = 0;
private var newRed:Number = 0;
private var newGreen:Number = 0;
private var newBlue:Number = 0;
private var _easingSpeed:Number = 0.05;
private var flag:Boolean = false;
public function Sample0602()
{
_sprite = new Sprite( );
_sprite.graphics.beginFill(0xffffff);
_sprite.graphics.drawRect(-50, -50, 100, 100);
_sprite.graphics.endFill( );
_sprite.x = 100;
_sprite.y = 100;
addChild(_sprite);
addEventListener(Event.ENTER_FRAME, onEnterFrame);
addEventListener(MouseEvent.CLICK, onClick);
}
public function onEnterFrame(event:Event):void
{
if(flag)
{
var ctf:ColorTransform = _sprite.transform.colorTransform;
var _red1:Number = ctf.redMultiplier;
var _green1:Number = ctf.greenMultiplier;
var _blue1:Number = ctf.blueMultiplier;
newRed += (_red2 - _red1) * _easingSpeed;
newGreen += (_green2 - _green1) * _easingSpeed;
newBlue += (_blue2 - _blue1) * _easingSpeed;
_sprite.transform.colorTransform = new ColorTransform(newRed, newGreen, newBlue);
}
}
public function onClick(event:MouseEvent):void
{
_red2 = .5;
_green2 = .5;
_blue2 = 1;
flag = true;
}
}
}9. 字符串拼接
可以使用str += "abc"或str.concat("abc")，区别在于前者会改变原字符串，后者不会改变原字符串而是生成一个新的字符串
package {
import flash.display.Sprite;
public class Sample0603 extends Sprite
{
public function Sample0603()
{
var str:String = "abc";
str += "def";
trace(str);//abcdef
var newStr:String = str.concat("fox");
trace(str);//abcdef
trace(newStr);//abcdeffox
}
}
}10. 获取字符串中的子串
可以使用
substr(startIndex, length)
substring(startIndex, endIndex)
slice(startIndex, endIndex)
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