从零开始学习调用百度地图网页API：三、鼠标点击绘图功能

代码

<!DOCTYPE html>
<html>
<head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><meta name="viewport" content="initial-scale=1.0, user-scalable=no" /><style type="text/css">body, html, #allmap {width: 100%;height: 100%;overflow: hidden;margin: 0;font-family: "微软雅黑";}ul li {list-style: none;}.btn-wrap {z-index: 999;position: fixed;bottom: 40px;margin-left: 200px;padding: 1rem 1rem;border-radius: .25rem;background-color: #fff;box-shadow: 0 2px 6px 0 rgba(27, 142, 236, 0.5);}.btn {width: 75px;height: 30px;float: left;background-color: #fff;color: rgba(27, 142, 236, 1);font-size: 14px;border: 1px solid rgba(27, 142, 236, 1);border-radius: 5px;margin: 0 5px;text-align: center;line-height: 30px;}.btn:hover {background-color: rgba(27, 142, 236, 0.8);color: #fff;}</style><script type="text/javascript" src="https://api.map.baidu.com/api?v=3.0&ak=你的ak"></script><title>显示坐标</title>
</head>
<body><div id="allmap"></div><ul class="btn-wrap" style="z-index: 999;"><li class="btn" id="plot_button" onclick="draw()">绘图</li><li class="btn" id="clear_button" onclick="clearpoint()">清除</li><li class="btn" id="show_pos_button" onclick="display()">显示坐标</li><li class="btn" id="not_show" onclick="notshow()">不显示</li></ul>
</body>
</html>
<script type="text/javascript">var drawflag = 0;var latline = new Array();var lonline = new Array();var line = new Array();var colorline = "blue";var show_flag = null;// 百度地图API功能var map = new BMap.Map("allmap");  // 创建Map实例map.centerAndZoom("北京", 15);      // 初始化地图,用城市名设置地图中心点var opts = {width: 20,     // 信息窗口宽度height: 5,     // 信息窗口高度}//var a = new Array(BMAP_SATELLITE_MAP,BMAP_NORMAL_MAP);var cursor = map.getDefaultCursor();map.enableScrollWheelZoom();//开启鼠标滚轮缩放var mapControl = new BMap.MapTypeControl({ mapTypes: [BMAP_NORMAL_MAP, BMAP_HYBRID_MAP, BMAP_SATELLITE_MAP] });map.addControl(mapControl);var scaleCtrl = new BMap.ScaleControl();  // 添加比例尺控件map.addControl(scaleCtrl);var cityCtrl = new BMap.CityListControl();  // 添加城市列表控件map.addControl(cityCtrl);//map.getUiSettings().setCompassEnabled(true);map.addEventListener("click", function (e) {addpoint(e.point.lng, e.point.lat);});function setMouse() {if (drawflag == 1)map.setDefaultCursor('crosshair');elsemap.setDefaultCursor(cursor);}function draw() {if (drawflag == 0)drawflag = 1;elsedrawflag = 0;setMouse();}//显示坐标信息窗口槽函数function showinfo(e) {var infoWindow = new BMap.InfoWindow(e.point.lat.toFixed(3) + ", " + e.point.lng.toFixed(3), opts);  // 创建信息窗口对象map.openInfoWindow(infoWindow, e.point);}//添加事件function display() {if (show_flag == null) {map.addEventListener('click', showinfo, false);show_flag = 1;}}//移除事件function notshow() {map.removeEventListener('click', showinfo);map.closeInfoWindow();show_flag = null;}function addpoint(lon, lat) {var k = 0;if (drawflag == 1) {line = new Array();latline.push(lat);lonline.push(lon);for (var i = 0; i < latline.length - 1; i++) {plot_line(lonline[i], latline[i], lonline[i + 1], latline[i + 1])k = i + 1;}var marker = new BMap.Marker(new BMap.Point(lon, lat));var point = new BMap.Point(lon, lat);map.addOverlay(marker);marker.addEventListener('click', function () {var opts = {title: `<font color='blue'>位置信息</font>`,};var info = '名称：坐标点' + k + "</br>坐标：" + point.lat.toFixed(5) + ", " + point.lng.toFixed(5);var infoWindow = new BMap.InfoWindow(info, opts);  // 创建信息窗口对象map.openInfoWindow(infoWindow, point);});}}function plot_line(lon1, lat1, lon2, lat2) {//起始点的经纬度//终止点的经纬度var polyline1 = new BMap.Polyline([new BMap.Point(lon1, lat1),new BMap.Point(lon2, lat2)], {strokeColor: "red",//设置颜色strokeWeight: 5, //宽度strokeOpacity: 1});//透明度map.addOverlay(polyline1);polyline1.addEventListener('click', function () {var opts = {title: `<font color='red'>距离</font>`,};var len_point = new BMap.Point((polyline1.mv.kf.lng + polyline1.mv.nf.lng) / 2.0, (polyline1.mv.kf.lat + polyline1.mv.nf.lat) / 2.0);var infoWindow = new BMap.InfoWindow("长度", opts);map.openInfoWindow(infoWindow, len_point);});polyline1.disableMassClear();line.push(polyline1);}function clearpoint() {var lines = map.getOverlays();//var allOverlay = map.getOverlays();for (var i = 0; i < lines.length; i++) {lines[i].enableMassClear();}map.clearOverlays();latline = new Array();lonline = new Array();line = new Array();}</script>

注：需要将你的ak替换，ak从百度地图官网注册申请，选择浏览器类型api。

功能

绘制线段
在这里插入图片描述
显示对象的位置信息

显示任意点坐标
在这里插入图片描述

问题注意

addEventListener

    //添加事件function display() {//alert(e.point.lng + ", " + e.point.lat);map.addEventListener('click', showinfo);}//移除事件function notshow() {map.closeInfoWindow();map.removeEventListener('click', showinfo);}

最初的实现方法，在显示坐标按钮多次被点击后，会导致再点击不显示按钮，无法remove事件。依然会在地图上点击后出现坐标信息。
这是因为addEventListener可以重复添加事件，为了避免重复添加事件，使用全局变量show_flag，通过值来判断是否已经添加过，若已经添加过事件，赋值为1，再次点击显示坐标按钮，不会重复添加事件。

    //添加事件function display() {if (show_flag == null) {map.addEventListener('click', showinfo, false);show_flag = 1;}}//移除事件function notshow() {map.removeEventListener('click', showinfo);map.closeInfoWindow();show_flag = null;}

plot_line

如果将函数内容直接在循环内实现，不使用函数。则polyline1变量在循环结束后调用addEventListener的值，只调用循环结束最后的结果。
不是每个循环都不同的值。
因此，写为函数。每个线段addEventListener为不同的值，在中点显示信息。

            for (var i = 0; i < latline.length - 1; i++) {plot_line(lonline[i], latline[i], lonline[i + 1], latline[i + 1])k = i + 1;}

function plot_line(lon1, lat1, lon2, lat2) {//起始点的经纬度//终止点的经纬度var polyline1 = new BMap.Polyline([new BMap.Point(lon1, lat1),new BMap.Point(lon2, lat2)], {strokeColor: "red",//设置颜色strokeWeight: 5, //宽度strokeOpacity: 1});//透明度map.addOverlay(polyline1);polyline1.addEventListener('click', function () {var opts = {title: `<font color='red'>距离</font>`,};var len_point = new BMap.Point((polyline1.mv.kf.lng + polyline1.mv.nf.lng) / 2.0, (polyline1.mv.kf.lat + polyline1.mv.nf.lat) / 2.0);var infoWindow = new BMap.InfoWindow("长度", opts);map.openInfoWindow(infoWindow, len_point);});polyline1.disableMassClear();line.push(polyline1);}