openlayer拖动范围设定

var mapOptions = {
		projection : new OpenLayers.Projection('EPSG:4326'),
		maxExtent : new OpenLayers.Bounds(121.95669802850942,37.302124678674154,122.73295650645256,37.63564806886632),
//		maxExtent : new OpenLayers.Bounds(-180, -90, 180, 90),
		restrictedExtent:new OpenLayers.Bounds(121.95669802850942,37.302124678674154,122.73295650645256,37.63564806886632),
		units : "degrees",// 单位度
		controls : []
	// 清空控件
	};
	map = new OpenLayers.Map('map',mapOptions);