egret屏幕抖动效果

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/**
 * 屏幕抖动
 * @author shirln
 * @since 2018/11/27
 * 
 * Example:
 * 震动目标obj，1秒内震动20次，震动最大距离20
 * ShakeTool.getInstance().shakeObj(obj, 1, 20, 20);
 */
class ShakeTool {
    private static instance:ShakeTool;   //单例
    private initX:number;                //初始位置
    private initY: number;  
    private target:egret.DisplayObject;  //震动目标
    private maxDis: number;              //震动距离
    private count: number = 0;           //计时器次数
    private rate: number;                //一秒震动次数
    private timer:egret.Timer = new egret.Timer(1000);
    
    public static getInstance():ShakeTool{
        if(this.instance == null){
            this.instance = new ShakeTool();
        }
        return this.instance;
    }
    
    /**
     * 震动显示对象
     * @param        target    震动目标对象
     * @param        time      震动持续时长（秒）
     * @param        rate      震动频率(一秒震动多少次)
     * @param        maxDis    震动最大距离
     */
    public shakeObj(target: egret.DisplayObject,time: number,rate: number,maxDis: number): void {
        this.stop();
        this.target = target;
        this.initX = target.x;
        this.initY = target.y;
        this.maxDis = maxDis;
        this.count = time * rate;
        this.rate = rate;
    
        this.timer.delay = 1000/rate;
        this.timer.repeatCount = this.count;
        this.timer.addEventListener(egret.TimerEvent.TIMER,this.shaking, this);
        this.timer.addEventListener(egret.TimerEvent.TIMER_COMPLETE, this.shakeComplete, this);
        this.timer.reset();
        this.timer.start();
    }
    
    private shaking(): void {
        egret.Tween.removeTweens(this.target);
        this.target.x = this.initX - this.maxDis + Math.random()*this.maxDis*2;
        this.target.y = this.initY - this.maxDis +  Math.random()*this.maxDis*2;
        egret.Tween.get(this.target).to({x:this.initX, y:this.initY},999/this.rate);    
    }
    
    private shakeComplete(): void {
        if(this.target){
            egret.Tween.removeTweens(this.target);
            this.target.x = this.initX;
            this.target.y = this.initY;
            this.target = null;
        }
        this.timer.removeEventListener(egret.TimerEvent.TIMER,this.shaking,this);
        this.timer.removeEventListener(egret.TimerEvent.TIMER_COMPLETE,this.shakeComplete,this);
    }

    /**停止震动 */
    public stop(){
        this.shakeComplete();
    }

}

调用方法：

 //震动目标obj，1秒内震动20次，震动最大距离20
 ShakeTool.getInstance().shakeObj(obj, 1, 20, 20);