mapboxGL测量实现

概述

讲真，MapboxGL里面虽然有测量的功能，但是不太好用，于是就萌生了自己实现的方法。本文几个turf.js来说说mapboxGL中测量的实现。

效果

实现

1、实现思路

1. 按照绘制的流程，需要涉及到map的三个事件：click，dblclick，mousemove，其中click为绘制，dblclick为结束绘制，mousemove为绘制中。这样，定义一个状态标识isMeasure，在点击开始绘制的按钮的时候，将标识设置为true,在map的三个事件中都会根据这个标识判断是否为绘制状态。
2. 地图的展示分layer和marker来分别展示；
3. layer里面区分点和线(面)图层，以达到比较好的展示效果。

2、实现代码

1.样式

.measure-result {background-color: white;border-radius: 3px;height: 16px;line-height: 16px;padding: 0 3px;font-size: 12px;box-shadow: 0 0 0 1px #ccc;&.close {cursor: pointer;width: 14px;height: 14px;line-height: 16px;text-align: center;padding: 0;}
}

2.测量距离

function measureLength() {var isMeasure = true;// 禁止双击缩放map.doubleClickZoom.disable();map.getCanvas().style.cursor = 'default';function clearMeasure() {$(".measure-result").remove();var source = map.getSource('points');var json = {'type': 'FeatureCollection','features': []};if(source) {map.getSource('points').setData(json);map.getSource('line-move').setData(json);map.getSource('line').setData(json);}var sourceArea = map.getSource('points-area');if(sourceArea) {map.getSource('points-area').setData(json);map.getSource('line-area').setData(json);}}clearMeasure();var jsonPoint = {'type': 'FeatureCollection','features': []};var jsonLine = {'type': 'FeatureCollection','features': []};var points = [];const ele = document.createElement('div');ele.setAttribute('class', 'measure-result');const option = {element: ele,anchor: 'left',offset: [8, 0]};var tooltip = new mapboxgl.Marker(option).setLngLat([0, 0]).addTo(map);var markers = [];var source = map.getSource('points');if(source) {map.getSource('points').setData(jsonPoint);map.getSource('line-move').setData(jsonLine);map.getSource('line').setData(jsonLine);} else {map.addSource('points', {type: 'geojson',data: jsonPoint});map.addSource('line', {type: 'geojson',data: jsonLine});map.addSource('line-move', {type: 'geojson',data: jsonLine});map.addLayer({id: 'line-move',type: 'line',source: 'line-move',paint: {'line-color': '#ff0000','line-width': 2,'line-opacity': 0.65}});map.addLayer({id: 'line',type: 'line',source: 'line',paint: {'line-color': '#ff0000','line-width': 2,'line-opacity': 0.65}});map.addLayer({id: 'points',type: 'circle',source: 'points',paint: {'circle-color': '#ffffff','circle-radius': 3,'circle-stroke-width': 2,'circle-stroke-color': '#ff0000'}});}function addPoint(coords) {if(jsonPoint.features.length > 0) {var prev = jsonPoint.features[jsonPoint.features.length - 1];jsonLine.features.push({type: 'Feature',geometry: {type: 'LineString',coordinates: [prev.geometry.coordinates, coords]}});map.getSource('line').setData(jsonLine);}jsonPoint.features.push({type: 'Feature',geometry: {type: 'Point',coordinates: coords}});map.getSource('points').setData(jsonPoint);}function getLength(coords) {var _points = points.concat([coords]);var line = turf.lineString(_points);var len = turf.length(line);if(len < 1) {len = Math.round(len * 1000) + 'm';} else {len = len.toFixed(2) + 'km';}return len;}function addMeasureRes(coords) {const ele = document.createElement('div');ele.setAttribute('class', 'measure-result');const option = {element: ele,anchor: 'left',offset: [8, 0]};ele.innerHTML = points.length === 0 ? '起点' : getLength(coords);var marker = new mapboxgl.Marker(option).setLngLat(coords).addTo(map);markers.push(marker);}map.on('click', function (_e) {if(isMeasure) {var coords = [_e.lngLat.lng, _e.lngLat.lat];addMeasureRes(coords);addPoint(coords);points.push(coords);}});map.on('mousemove', function (_e) {if(isMeasure) {var coords = [_e.lngLat.lng, _e.lngLat.lat];if (jsonPoint.features.length > 0) {var prev = jsonPoint.features[jsonPoint.features.length - 1];var json = {type: 'Feature',geometry: {type: 'LineString',coordinates: [prev.geometry.coordinates, coords]}};map.getSource('line-move').setData(json);ele.innerHTML = getLength(coords);} else {ele.innerHTML = '点击地图开始测量';}tooltip.setLngLat(coords);}});map.on('dblclick', function (_e) {if(isMeasure) {var coords = [_e.lngLat.lng, _e.lngLat.lat];addPoint(coords);isMeasure = false;map.getCanvas().style.cursor = '';jsonPoint.features = [];jsonLine.features = [];tooltip.remove();// 添加关闭按钮const ele = document.createElement('div');ele.setAttribute('class', 'measure-result close');const option = {element: ele,anchor: 'bottom-left',offset: [-5, -10]};ele.innerHTML = '×';new mapboxgl.Marker(option).setLngLat(coords).addTo(map);ele.onclick = function (__e) {__e.stopPropagation();map.doubleClickZoom.enable();clearMeasure();}}});
}  

3.测量面积

function measureArea() {  var isMeasure = true;// 禁止双击缩放map.doubleClickZoom.disable();map.getCanvas().style.cursor = 'default';function clearMeasure() {$(".measure-result").remove();var source = map.getSource('points');var json = {'type': 'FeatureCollection','features': []};if(source) {map.getSource('points').setData(json);map.getSource('line-move').setData(json);map.getSource('line').setData(json);}var sourceArea = map.getSource('points-area');if(sourceArea) {map.getSource('points-area').setData(json);map.getSource('line-area').setData(json);}}clearMeasure();var jsonPoint = {'type': 'FeatureCollection','features': []};var jsonLine = {'type': 'FeatureCollection','features': []};var points = [];var ele = document.createElement('div');ele.setAttribute('class', 'measure-result');const option = {element: ele,anchor: 'left',offset: [8, 0]};var tooltip = new mapboxgl.Marker(option).setLngLat([0, 0]).addTo(map);var source = map.getSource('points-area');if(source) {map.getSource('points-area').setData(jsonPoint);map.getSource('line-area').setData(jsonLine);} else {map.addSource('points-area', {type: 'geojson',data: jsonPoint});map.addSource('line-area', {type: 'geojson',data: jsonLine});map.addLayer({id: 'line-area',type: 'fill',source: 'line-area',paint: {'fill-color': '#ff0000','fill-opacity': 0.1}});map.addLayer({id: 'line-area-stroke',type: 'line',source: 'line-area',paint: {'line-color': '#ff0000','line-width': 2,'line-opacity': 0.65}});map.addLayer({id: 'points-area',type: 'circle',source: 'points-area',paint: {'circle-color': '#ffffff','circle-radius': 3,'circle-stroke-width': 2,'circle-stroke-color': '#ff0000'}});}function getArea(coords) {var pts = points.concat([coords]);pts = pts.concat([points[0]]);var polygon = turf.polygon([pts]);var area = turf.area(polygon);if(area < 1000) {area = Math.round(area) + 'm²';} else {area = (area / 1000000).toFixed(2) + 'km²';}return area;}function addPoint(coords) {jsonPoint.features.push({type: 'Feature',geometry: {type: 'Point',coordinates: coords}});map.getSource('points-area').setData(jsonPoint);}map.on('click', function (_e) {if(isMeasure) {var coords = [_e.lngLat.lng, _e.lngLat.lat];points.push(coords);addPoint(coords);}});map.on('dblclick', function (_e) {if(isMeasure) {var coords = [_e.lngLat.lng, _e.lngLat.lat];points.push(coords);isMeasure = false;ele.innerHTML = getArea(coords);tooltip.setLngLat(coords);// 添加关闭按钮var _ele = document.createElement('div');_ele.setAttribute('class', 'measure-result close');var option = {element: _ele,anchor: 'bottom-left',offset: [-5, -10]};_ele.innerHTML = '×';new mapboxgl.Marker(option).setLngLat(coords).addTo(map);_ele.onclick = function (__e) {__e.stopPropagation();map.doubleClickZoom.enable();clearMeasure();}}});map.on('mousemove', function (_e) {if(isMeasure) {var coords = [_e.lngLat.lng, _e.lngLat.lat];var len = jsonPoint.features.length;if (len === 0) {ele.innerHTML = '点击地图开始测量';} else if (len ===1) {ele.innerHTML = '点击地图继续绘制';} else {var pts = points.concat([coords]);pts = pts.concat([points[0]]);var json = {type: 'Feature',geometry: {type: 'Polygon',coordinates: [pts]}};map.getSource('line-area').setData(json);ele.innerHTML = getArea(coords);}tooltip.setLngLat(coords);}});
}