用openlayer是交互画一个点、线、面，执行回调函数

graphicLayer 是一个vector图层。

callback是回调函数。

调用方法如下：

 if (typeof newlayer != 'undefined' && newlayer != null) {
                    var dg = new DiliGISApi.DrawGraphic(newlayer.Layer);
                    var calback = function(line) {
                        var pointCount = line.Value.length;
                        for (var i = 0; i <= pointCount - 1; i++) {
                            alert(line.Value[i][0] + "," + line.Value[i][1]);
                        }
                    }
                    dg.DrawPolygon(calback);
                } else {
                    alert("create layer first");
                }

画图类如下：

var DiliGISApi = DiliGISApi ? DiliGISApi : {};
DiliGISApi.DrawGraphic = function(graphicLayer) {
    ///

用于交互画地图对象/summary>
    var _this = this;
    var layer = graphicLayer;
    /*
    * 返回点对象
    */
    _this.DrawPoint = function(callback) {
        ///

画点

        try {
            var drawPointCtrol = new OpenLayers.Control.DrawFeature(layer, OpenLayers.Handler.Point);
            drawPointCtrol.featureAdded = function(feature) {
                try {
                    feature.layer.eraseFeatures([feature]);
                    var point = new DiliGISApi.Point(feature.geometry.x, feature.geometry.y);
                    callback(point);
                    drawPointCtrol.deactivate();
                    layer.map.removeControl(drawPointCtrol);
                } catch (e) {
                    alert("drawPointCtrol->:" + e.name + "," + e.message);
                }
            }
            layer.map.addControl(drawPointCtrol);
            drawPointCtrol.activate();


        } catch (e) {
            alert("DrawPoint->:" + e.name + "," + e.message);
        }
    };


    /*
    * 返回线对象
    */
    _this.DrawLine = function(callback) {
        try {
            var drawLineCtrol = new OpenLayers.Control.DrawFeature(layer, OpenLayers.Handler.Path);
            drawLineCtrol.featureAdded = function(feature) {
                try {
                    feature.layer.eraseFeatures([feature]);
                    var pts = feature.geometry.components;
                    var points = [];
                    var pointCount = pts.length;
                    for (var i = 0; i <= pointCount - 1; i++) {
                        points.push([pts[i].x, pts[i].y]);
                    }
                    var polyline = new DiliGISApi.PolyLine(points);
                    callback(polyline);
                    drawLineCtrol.deactivate();
                    layer.map.removeControl(drawLineCtrol);
                } catch (e) {
                    alert("drawLineCtrol->:" + e.name + "," + e.message);
                }
            }
            layer.map.addControl(drawLineCtrol);
            drawLineCtrol.activate();

        } catch (e) {
            alert("DrawLine->:" + e.name + "," + e.message);
        }
    };
    /*
    * 返回面对象
    */
    _this.DrawPolygon = function(callback) {
        try {

            var drawPolygonCtrol = new OpenLayers.Control.DrawFeature(layer, OpenLayers.Handler.Polygon);
            drawPolygonCtrol.featureAdded = function(feature) {
                try {
                    feature.layer.eraseFeatures([feature]);
                    var pts = feature.geometry.components[0].components;
                    var points = [];
                    var pointCount = pts.length;
                    for (var i = 0; i <= pointCount - 1; i++) {
                        points.push([pts[i].x, pts[i].y]);
                    }
                    var polygon = new DiliGISApi.Polygon(points);
                    callback(polygon);
                    drawPolygonCtrol.deactivate();
                    layer.map.removeControl(drawPolygonCtrol);
                } catch (e) {
                    alert("drawPolygonCtrol->:" + e.name + "," + e.message);
                }
            }
            layer.map.addControl(drawPolygonCtrol);
            drawPolygonCtrol.activate();

        } catch (e) {
            alert("DrawPolygon->:" + e.name + "," + e.message);
        }
    };
};