此代码只能实现鼠标点击 才会弹出信息窗口

我需要打开地图就让它自己显示信息窗口，然后可以手动关闭和开启

/**

* 加载卫星地图并作标记

* 点击标记可弹出信息窗

*/

function init() {

var map = new sogou.maps.Map(document.getElementById("map_canvas"), {

scaleControl: true});

map.setCenter(new sogou.maps.Point(115.77563369169235,38.68891128623845),16);

var marker = new sogou.maps.Marker({map: map, position:

map.getCenter()});

var infowindow = new sogou.maps.InfoWindow();

infowindow.setContent('

');

sogou.maps.event.addListener(marker, 'click', function() {

infowindow.open(map, marker);

});

}