openlayers4.6.5实现距离量测和面积量测

var draw;
var click=false;
var output=0;
var vector;
var source;
var lastPolygonLabelFeature;//记录上一个面标注要素 
var lastLengthLabelFeature;//记录上一个点标注要素
$(
 function(){
 $("#measureDistance").click(function(){
 if(draw){
 map.removeInteraction(draw); 
 }
 addInteraction("length");
 setMeasureCur();
 })
 $("#measureArea").click(function(){
 if(draw){
 map.removeInteraction(draw); 
 }
 addInteraction("area"); 
 setMeasureCur();
 })
 $("#measureClear").click(function(){
 map.removeInteraction(draw); 
 vector.setSource(null);
 source=new ol.source.Vector();
 vector.setSource(source);
 lastPolygonLabelFeature=null;
 lastLengthLabelFeature=null;
 click=false;
 
 sketch = null;
 output="0";
 
 reSetCur();
 })
 function setMeasureCur(){
 $('#map').css({
 cursor:"url(../../static/images/measureIcon/measure.cur), auto"
 });
 }
 
 function reSetCur(){
 $('#map').css('cursor','default');
 }
 
 source = new ol.source.Vector();
 vector = new ol.layer.Vector({
 source: source,
 style: new ol.style.Style({
 fill: new ol.style.Fill({//面的填充颜色
 color: 'rgba(255, 0, 0, 0.1)'
 }),
 stroke: new ol.style.Stroke({
 color: 'rgb(255,116,3)',
 width: 2
 }),
 image: new ol.style.Circle({
 radius: 3,
 stroke: new ol.style.Stroke({
 color: 'rgba(255, 0, 0,1)',
 width: 2
 }),
 fill: new ol.style.Fill({
 color: 'rgba(255,255,255)'
 })
 
 })
 })
 });
 map.addLayer(vector);
 
 var sketch;
 
 var pointerMoveHandler = function(evt) {
 if (evt.dragging) {
 return;
 }
 var Coord;
 
 if(sketch){
 var geom = sketch.getGeometry();
 if (geom instanceof ol.geom.Polygon) {
 
 if(lastPolygonLabelFeature){
  //鼠标移动 不停的添加和删除
 source.removeFeature(lastPolygonLabelFeature);
 }
 
 Coord = geom.getInteriorPoint().getCoordinates();
 
 //新建一个要素ol.Feature
 var newFeature = new ol.Feature({
  geometry: new ol.geom.Point(Coord), //几何信息
  name: output
 });
 lastPolygonLabelFeature=newFeature; 
 newFeature.setStyle(createLabelStyle(newFeature,0,0)); 
 } else if (geom instanceof ol.geom.LineString) {
 if(lastLengthLabelFeature){
 source.removeFeature(lastLengthLabelFeature);
 }
 
 Coord = geom.getLastCoordinate();
 //新建一个要素ol.Feature
 var newFeature = new ol.Feature({
  geometry: new ol.geom.Point(Coord), //几何信息
  name: output
 });
 lastLengthLabelFeature=newFeature;
 newFeature.setStyle(createLabelStyle(newFeature,35,-10)); 
 }
 //设置要素样式
 source.addFeature(newFeature);
 }
 };
 
 map.on('pointermove', pointerMoveHandler);
 map.on('click', function(evt){
 var coordinate = evt.coordinate; //鼠标单击点的坐标
 console.log(coordinate);
 if(output=="0"){
 lastPolygonLabelFeature=null;
 if(lastLengthLabelFeature){
 source.removeFeature(lastLengthLabelFeature);
 lastLengthLabelFeature=null;
 }
 return;
 }
 
 var Coord;
 if(sketch){
 var geom = sketch.getGeometry();
 if (geom instanceof ol.geom.Polygon) {
 
 if(lastPolygonLabelFeature){
 source.removeFeature(lastPolygonLabelFeature);
 }
 Coord = geom.getInteriorPoint().getCoordinates();
 
 //新建一个要素ol.Feature
 var newFeature = new ol.Feature({
  geometry: new ol.geom.Point(Coord), //几何信息
  name: output
 });
 lastPolygonLabelFeature=newFeature;
 newFeature.setStyle(createLabelStyle(newFeature,0,0)); //设置要素样式
 source.addFeature(newFeature);
 
 
 } else if (geom instanceof ol.geom.LineString) {
 
 Coord = geom.getLastCoordinate();
 //新建一个要素ol.Feature
 var newFeature = new ol.Feature({
  geometry: new ol.geom.Point(Coord), //几何信息
  name: output
 });
 newFeature.setStyle(createLabelStyle(newFeature,35,-10)); //设置要素样式
 source.addFeature(newFeature);
 }
 
 var pointFeature = new ol.Feature({
 geometry: new ol.geom.Point(coordinate), //几何信息
 name: output
 });
 source.addFeature(pointFeature);
 }
 
 });
 
 //矢量标注样式设置函数，设置image为图标ol.style.Icon
 function createLabelStyle(feature,offsetX,offsetY){
 return new ol.style.Style({
// image: new ol.style.Icon({
//  anchor: [0.5, 60], //锚点
//  anchorOrigin:'top-right', //锚点源
//  anchorXUnits: 'fraction', //锚点X值单位
//  anchorYUnits: 'pixels', //锚点Y值单位
//  offsetOrigin: 'top-right', //偏移原点
//  opacity: 0.75,
//  src: 'OL3Demo/images/label/blueIcon.png' //图标的URL
// }),
 text: new ol.style.Text({
  textAlign: 'center', //位置
  textBaseline: 'middle', //基准线
  font: 'normal 10px sans-serif', //文字样式
  text: feature.get('name'), //文本内容
  fill: new ol.style.Fill({ //文本填充样式（即文字颜色)
  color: 'white'
  }),
  stroke: new ol.style.Stroke({
  color: 'black', 
  width: 5
  }),
  offsetX:offsetX,
  offsetY:offsetY
 
 })
 });
 }
 
 
 
 function addInteraction(drawType) {
 var type = (drawType== 'area' ? 'Polygon' : 'LineString');
 draw = new ol.interaction.Draw({
 source: source,
 type: type,
 style: new ol.style.Style({
 fill: new ol.style.Fill({
 color: 'rgba(255, 0, 0, 0.2)'
 }),
 stroke: new ol.style.Stroke({
 color: 'rgb(255,116,3)',
// lineDash: [10, 10],//虚线
 width: 2
 }),
 image: new ol.style.Circle({
 radius: 5,
 stroke: new ol.style.Stroke({
 color: 'rgba(255, 0, 0, 0.1)'
 }),
 fill: new ol.style.Fill({
 color: 'rgba(255,116,3, 0.3)'
 })
 })
 })
 });
 map.addInteraction(draw);
 
 var listener;
 draw.on('drawstart',
 function(evt) {
 // set sketch
 sketch = evt.feature;
 listener = sketch.getGeometry().on('change', function(evt) {
 var geom = evt.target;
 
 if (geom instanceof ol.geom.Polygon) {
  output = formatArea(geom);
 } else if (geom instanceof ol.geom.LineString) {
  output = formatLength(geom);
 }
 
 });
 }, this);
 
 draw.on('drawend',
 function() {
 // unset sketch
 sketch = null;
 ol.Observable.unByKey(listener);
 output="0";
 }, this);
 }
 
 var formatLength = function(line) {
 var length = ol.Sphere.getLength(line);
 var output;
 if (length > 100) {
 output = (Math.round(length / 1000 * 100) / 100) +
 ' ' + '千米';
 } else {
 output = (Math.round(length * 100) / 100) +
 ' ' + '米';
 }
 return output;
 };
 
 var formatArea = function(polygon) {
 var area = ol.Sphere.getArea(polygon);
 var output;
 if (area > 10000) {
 output = (Math.round(area / 1000000 * 100) / 100) +
 ' ' + '平方千米';
 } else {
 output = (Math.round(area * 100) / 100) +
 ' ' + '平方米';
 }
 return output;
 };
})