function getBoundary(districtName)
{  
    var bdary = new BMap.Boundary();
    var name = districtName; 
    if(districtName=="马鞍山市"||"雨山区"||"花山区"||"金家庄区")
      bdary.get(districtName, function(rs)
       {       //获取行政区域
        map.clearOverlays();        //清除地图覆盖物       
        var count = rs.boundaries.length; //行政区域的点有多少个
        for(var i = 0; i < count; i++){
            var ply = new BMap.Polygon(rs.boundaries[i], {strokeWeight: 2, strokeColor: "#ff0000"}); //建立多边形覆盖物
            map.addOverlay(ply);  //添加覆盖物
            map.setViewport(ply.getPath());    //调整视野         
        }
     });
     else
         secRing();   
}