一些功能方法

判断坐标点是否在视野范围内

function getFourPoints (target) { //target格式：new AMap.LngLat( 116.491272,39.95527 ) 
    var bounds = map.getBounds();          
  var NorthEast = bounds.getNorthEast();
  var SouthWest = bounds.getSouthWest();
  var SouthEast = [NorthEast.lng, SouthWest.lat];
  var NorthWest = [SouthWest.lng, NorthEast.lat];
  var path = [[NorthEast.lng, NorthEast.lat], SouthEast, [SouthWest.lng, SouthWest.lat], NorthWest]
  var inRing = AMap.GeometryUtil.isPointInRing(target,  path);
  return inRing
}