294 lines
14 KiB
HTML
294 lines
14 KiB
HTML
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<!DOCTYPE html>
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0" />
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<meta name="apple-mobile-web-app-capable" content="yes" />
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<title>动画渲染专题</title>
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<link href='./css/bootstrap.min.css' rel='stylesheet' />
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<link href='./css/bootstrap-responsive.min.css' rel='stylesheet' />
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<link href='./css/sm-extend.css' rel='stylesheet' />
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<link href='./css/sm-doc.css' rel='stylesheet' />
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</head>
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<body data-spy="scroll" data-target=".subnav" data-offset="50">
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<!--导航条-->
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<div class="navbar navbar-fixed-top" id="navbar">
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</div>
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<div id='container' class='container'>
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<div class='page-header'>
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<h1 style="margin-top: 2%">客户端高性能矢量渲染专题</h1>
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<hr />
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<h2>一、高性能矢量渲染图层Vector类简介</h2>
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<p>
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SuperMap iClient for JavaScript 提供的 Vector 类支持采用 HTML5 的 Canvas
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元素渲染矢量数据，并且提供了对渲染要素的添加、删除和选择操作，
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从而为大数据量的矢量数据在无插件的 HTML 文档中，平滑、流畅的呈现，提供了新的解决方案。
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</p>
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<h2>二、高性能矢量渲染图层 Vector 类的使用说明</h2>
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<p> Vector 类用 addFeatures、removeFeatures、removeAllFeatures、
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redraw、getFeatureBy、 getFeatureById、getFeatureByFid、 getFeaturesByAttribute
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等方法实现对要素的添加、删除、获取，方法的具体介绍和详细的使用说明请参见《API文档》，
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下面以具体实例---<strong>车辆监控系统</strong>说明 Vector 的使用方法：
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</p>
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<p> 长春市某公交公司现有797辆车在28条公交
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线路上正常运作运送乘客，为了满足车辆安防和调度的需要， 现对797辆车进行实时监控，
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进而达到降低运营成本、提高服务水平、提高企业 收益的目的。此实例通过使用 Vector 类的接口实现了
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对大量车辆的实时在线查询和更新功能。
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</p>
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<h3>2.1、查询功能</h3>
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<p>
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电子地图上实时显示797辆车，公交公司管理部门可以远程监控所有车辆，具体实现方法如下：
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</p>
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<p>
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(1).初始化两个图层 vectorLayer、vectorLayerCars，一个作为公交车路线图层，一个作为公交车图层。
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</p>
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<pre>
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//初始化公交车路线图层
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vectorLayer = new SuperMap.Layer.Vector("Vector Layer", {
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renderers: ["Canvas"],
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styleMap: new SuperMap.StyleMap({"default": styleLine})
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});
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//初始化公交车图层
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vectorLayerCars = new SuperMap.Layer.Vector("Vector Layer Cars", {
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renderers: ["Canvas2"],
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styleMap: new SuperMap.StyleMap({"default": stylePoint})
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});
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//为 vectorLayerCars 添加一个选择控件。
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select = new SuperMap.Control.SelectFeature(vectorLayerCars, {
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onSelect: onFeatureSelect,
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onUnselect: onFeatureUnselect
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}
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);
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map.addControl(select);
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//要素被选中时调用此函数
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function onFeatureSelect(feature) {
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selecedtBus = feature;
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popup = new SuperMap.Popup("chicken",
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selecedtBus.geometry.getBounds().getCenterLonLat(),
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new SuperMap.Size(300,42),
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"<div style='font-size:.8em; opacity: 0.8'><p>公交线路：" + selecedtBus.line.num + "路" +
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"</p><p>当前位置：" + selecedtBus.geometry.x + "，" + selecedtBus.geometry.y + "</p></div>", null, true);
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selecedtBus.popup = popup;
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map.addPopup(popup);
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}
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//清除要素时调用此函数
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function onFeatureUnselect(feature) {
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map.removePopup(feature.popup);
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feature.popup.destroy();
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feature.popup = null;
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selecedtBus = null;
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}
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</pre>
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<p>
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(2).定义查询的公交车路线，通过 SQL 查询方法查询公交路线,通过监听对 QueryBySQLService 支持的
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两个从服务端返回结果事件 processCompleted 、processFailed，获取查询公交路线结果。
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</p>
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<pre>
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//定义查询公交线路
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function queryBySQL() {
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//清除当前图层所有feature要素
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vectorLayer.removeAllFeatures();
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var queryParam, queryBySQLParams, queryBySQLService;
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//声明查询参数
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queryParam = new SuperMap.REST.FilterParameter({
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name: "BusLine@Changchun#1",
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attributeFilter: "SmID > 0"}
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),
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//声明 SQL 查询参数，将 queryParam 赋给 queryBySQLParams
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queryBySQLParams = new SuperMap.REST.QueryBySQLParameters({
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queryParams: [queryParam]
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}),
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//声明 SQL 服务对象
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queryBySQLService = new SuperMap.REST.QueryBySQLService(url, {
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eventListeners: {
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"processCompleted": processCompleted,
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"processFailed": processFailed
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}
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});
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//向服务端发送请求执行查询
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queryBySQLService.processAsync(queryBySQLParams);
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}
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</pre>
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<p>
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(3). 定义 QueryBySQLService 的监听对象，用于显示公交路线图层和公家车图层，实现过程中
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需要先分别定义一个公交路线的数组和公交车的数组，然后通过公交路线节点模拟公交车，
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实例化公交车的运行方向和位置，最后添加公交车路线图层和公交车图层。
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</p>
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<pre>
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function processCompleted(queryEventArgs) {
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var i, j, feature,
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result = queryEventArgs.result;
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features = [];
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cars = [];
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orientation = 1;
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if (result && result.recordsets) {
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for (i=0; i<result.recordsets.length; i++) {
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if (result.recordsets[i].features) {
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for (j=0; j<result.recordsets[i].features.length; j++) {
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feature = result.recordsets[i].features[j];
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feature.style = null;
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feature.num = j;
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features.push(feature);
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for(var k = 0, len = feature.geometry.components.length; k < len; k++) {
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//创建公交车对象
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var car = new SuperMap.Feature.Vector(feature.geometry.components[k].clone());
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//定义公交车的 style
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car.style = {pointRadius: 10, stroke: false};
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var cargeometry = car.geometry;
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//定义公交车基本信息,包括公交车的路线、速度和速度向量、当前节
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//点位置和下一结点位置、通过速度向量计算的旋转角度、移动步数
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car.line = feature;
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car.orientation = orientation;
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car.currentIndex = k;
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if(feature.geometry.components[car.currentIndex + car.orientation]) {
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car.nextPoint = feature.geometry.components[k + car.orientation];
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var dx = car.nextPoint.x - cargeometry.x;
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var dy = car.nextPoint.y - cargeometry.y;
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var distance = Math.sqrt(dx * dx + dy * dy);
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car.speed = parseInt(Math.random() * 5 + 2) * car.orientation;
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if(car.speed == 0) {car.speed == 10};
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car.moves = distance / car.speed;
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car.vx = dx / car.moves;
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car.vy = dy / car.moves;
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var angle = Math.atan2(dx, dy);
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car.style.rotate = angle;
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//分配不同的公交车图片
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if (Math.abs(car.speed < 4)){
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car.style.externalGraphicSource = car1;
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}
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if (Math.abs(car.speed) >= 4 && Math.abs(car.speed < 5)){
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car.style.externalGraphicSource = car2;
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}
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if (Math.abs(car.speed >= 5)){
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car.style.externalGraphicSource = car3;
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}
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car.stop = false;
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}else{
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car.stop = true;
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car.style.externalGraphicSource = car3;
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}
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orientation *= -1;
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cars.push(car);
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}
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}
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}
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}
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}
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//将公交路线绘制到公交路线图层上
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vectorLayer.addFeatures(features);
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//将公交车绘制公交车图层上
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vectorLayerCars.addFeatures(cars);
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}
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</pre>
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<p>显示效果图如下所示：</P>
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<div class="pageImage"><img src="./images/bus.png" /></div>
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<h3>2.2大量车辆实时在线更新功能 </h3>
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<p>
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公交公司管理部门监控某一时间段内797辆车的运行状态 , 电子地图上显示每辆车每30秒的位置变化情况，实现代码如下：
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</p>
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<p>
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（1）开始实施监控，通过公交车的基本信息（如速度，定位信息）改变其位置，实施方法为先全部
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清除(removeAllFeatures)显示公交车的图层，再定义公交车的属性信息(方向、速度等)，
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最后将改变后的公交车数组通过 addFeatures 方法加入至公交车图层。
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</p>
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<pre>
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//开始监控
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function monitor() {
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document.getElementById("monitor").onclick = "";
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if(selecedtBus) {
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map.removePopup(selecedtBus.popup);
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}
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vectorLayerCars.removeAllFeatures();
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redraw = false;
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for(var i =0, len = cars.length; i < len; i++) {
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var car = cars[i];
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var cargeometry = car.geometry;
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if(!car.stop) {
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if(car.moves < 1) {
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cargeometry.x = car.nextPoint.x;
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cargeometry.y = car.nextPoint.y;
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//更新公交车的信息
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var feature = car.line;
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car.currentIndex += car.orientation;
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if(feature.geometry.components[car.currentIndex + car.orientation]) {
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car.nextPoint = feature.geometry.components[car.currentIndex + car.orientation];
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var dx = car.nextPoint.x - cargeometry.x;
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var dy = car.nextPoint.y - cargeometry.y;
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var distance = Math.sqrt(dx * dx + dy * dy);
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car.moves = Math.abs(distance / car.speed);
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car.vx = dx / car.moves;
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car.vy = dy / car.moves;
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var angle = Math.atan2(dx, dy);
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car.style.rotate = angle;
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}else{
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car.stop = true;
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car.style.fillColor = "rgb(150,150,150)";
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}
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}else{
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cargeometry.x += car.vx;
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cargeometry.y += car.vy;
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car.moves--;
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}
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}
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//只要有车移动就需要重绘。
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if(!car.stop) {
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redraw = true;
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}
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}
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//将公交车绘制到公交车图层上
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vectorLayerCars.addFeatures(cars);
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if(selecedtBus) {
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//将选中的公交车的信息添加到地图上
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vectorLayerCars.selectedFeatures.push(selecedtBus);
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popup = new SuperMap.Popup("chicken",
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selecedtBus.geometry.getBounds().getCenterLonLat(),
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new SuperMap.Size(300,42), "<div style='font-size:.8em; opacity: 0.8'><p>公交线路：" +
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selecedtBus.line.num + "路" +
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"</p><p>当前位置：" + selecedtBus.geometry.x + "，" + selecedtBus.geometry.y + "</p></div>",
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null, true);
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selecedtBus.popup = popup;
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map.addPopup(popup);
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}
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}
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</pre>
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<p>（2）通过监听公交车图层的 feature 添加完成事件(addFeaturesCompelte)，
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以实时调用 clearFeatures 方法实现公交车的动态监控。
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</p>
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<pre>
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function addFeaturesCompelte(args) {
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if(redraw) {
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timerid = setTimeout(monitor, 50);
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}
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}
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</pre>
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<p>（3） 通过 onclick 事件停止监控。
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</p>
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<pre>
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//停止监控
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function stopMonitor() {
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window.clearTimeout(timerid);
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document.getElementById("monitor").onclick = monitor;
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redraw = false;
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}
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</pre>
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<h2>三、专题小结</h2>
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<p>以上车辆监控实例通过高性能矢量渲染 Vector 类实现了对大量车辆的在线查询和
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实时更新功能，满足了用户需求的同时，也带给用户平滑、流畅的视觉效果。
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</p>
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<p>通过实例也验证了高性能矢量绘制图层 Vector 类在大量数据显示、
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实时更新等功能上的优异性能和流畅稳定的呈现，
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为用户提供了客户端大量动态数据展示的解决方案。
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</p>
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</div>
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<div class='footer'>
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<p>版权所有 © 2000-2016 北京超图软件股份有限公司</p>
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</div>
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</div>
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<script src='./js/jquery.js'></script>
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<script src='./js/bootstrap.js'></script>
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<script src="./js/navbar.js"></script>
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<script src="./js/GoTop.js" id="js_gotop"></script>
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</body>
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</html>
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