百度地图JavascriptApi Marker平滑移动及车头指向行径方向

/*
 *缓动效果
 *初始坐标，目标坐标，当前的步长，总的步长
 *@param{BMap.Pixel} initPos 初始平面坐标
 *@parm{BMap.Pixel} targetPos 目标平面坐标
 *@param{number} 当前帧数
 *@param {number} count 总帧数
 */
 this.linear = function (initPos, targetPos, currentCount, count) {
  var b = initPos, c = targetPos - initPos, t = currentCount,
  d = count;
  return c * t / d + b;
 }
　　 var x = effect(_prvePoint.x, _newPoint.x, currentCount, count),
  y = effect(_prvePoint.y, _newPoint.y, currentCount, count);

/**
 *小车移动
 *@param {Point} prvePoint 开始坐标(PrvePoint)
 *@param {Point} newPoint 目标点坐标
 *@param {Function} 动画效果
 *@return 无返回值
 */
 this.Move = function (prvePoint, newPoint, effect, setRotation) {
  var me = this,
    //当前帧数
    currentCount = 0,
    //初始坐标
    _prvePoint = me._projection.lngLatToPoint(prvePoint),//将球面坐标转换为平面坐标
    //获取结束点的(x,y)坐标
    _newPoint = me._projection.lngLatToPoint(newPoint),
    //两点之间要循环定位的次数
    count = me._runTime / me._intervalTimer;
    //两点之间匀速移动
    me._intervalFlag = setInterval(function () {
     //两点之间当前帧数大于总帧数的时候，则说明已经完成移动
     if (currentCount >= count) {
     clearInterval(me._intervalFlag);
     } else {
    //动画移动
    currentCount++;//计数
      var x = effect(_prvePoint.x, _newPoint.x, currentCount, count),
       y = effect(_prvePoint.y, _newPoint.y, currentCount, count);
      //根据平面坐标转化为球面坐标
    var pos = map.getMapType().getProjection().pointToLngLat(new BMap.Pixel(x, y));
    //设置marker角度(两点之间的距离车的角度保持一致)
     if (currentCount == 1) {
      //转换角度                     setRotation(prvePoint,newPoint, me._em);
     }
      //正在移动
    me._em._newPointMark.setPosition(pos);
   }
    }, me._intervalTimer);
    me._em._prvePoint = newPoint;
 }

/**
 *在每个点的真实步骤中设置小车转动的角度
 *@param{BMap.Point} curPos 起点
  *@param{BMap.Point} targetPos 终点
 */
  this.setRotation = function (curPos, targetPos, em)
  {
   var me = this;
   var deg = 0;
   curPos = map.pointToPixel(curPos);
   targetPos = map.pointToPixel(targetPos);
   if (targetPos.x != curPos.x) {
    var tan = (targetPos.y - curPos.y) / (targetPos.x - curPos.x),
    atan = Math.atan(tan);
    deg = atan * 360 / (2 * Math.PI);
    if (targetPos.x < curPos.x) {
     deg = -deg + 90 + 90;
    } else {
     deg = -deg;
    }
    em._newPointMark.setRotation(-deg);
   } else {
    var disy = targetPos.y - curPos.y;
    var bias = 0;
    if (disy > 0)
     bias = -1
    else
     bias = 1
    em._newPointMark.setRotation(-bias * 90);
   }
   return;
  }