打开图层 - 仅显示高于特定缩放级别的图层

Question

我正在制作具有不同矢量图层的开放图层地图。我想添加一个功能，即某个矢量层仅在特定的缩放值下显示，例如在缩放>= 18 时。我尝试使用minZoom和minScale/maxScale功能，但它不起作用。我想在缩放级别>= 18 显示的矢量层称为"dach 层"。我还尝试使用 if 函数解决它：

// dach layer anzeigen versuch
const dach = document.getElementById('dach');
dach.addEventListener('click', function (event) {
var checkBox = document.getElementById("dach");
if (checkBox.checked == true) {
if (map.getZoom() > 17) {
dachLayer.setMap(map);
//hitzeLayer.setVisible(true);
}
} else {
//hitzeLayer.setVisible(false);
dachLayer.setMap(undefined);
}
}); 

这是我使用的代码：

import 'ol/ol.css';
import Map from 'ol/Map';
import View from 'ol/View';
import TileLayer from 'ol/layer/Tile';
import Stamen from 'ol/source/Stamen';
import VectorLayer from 'ol/layer/Vector';
import Vector from 'ol/source/Vector';
import GeoJSON from 'ol/format/GeoJSON';
import Style from 'ol/style/Style';
import Circle from 'ol/style/Circle';
import Fill from 'ol/style/Fill';
import Stroke from 'ol/style/Stroke';
import Overlay from 'ol/Overlay';
import {
fromLonLat,
toLonLat
} from 'ol/proj';
import sync from 'ol-hashed';
import OSM from 'ol/source/OSM';
import Feature from 'ol/Feature';
import {
circular
} from 'ol/geom/Polygon';
import Point from 'ol/geom/Point';
import Control from 'ol/control/Control';
import * as olProj from 'ol/proj';
import XYZ from 'ol/source/XYZ';
// define the map
const map = new Map({
target: 'map',
view: new View({
center: fromLonLat([16.37, 48.2]),
zoom: 13
})
});
sync(map);
//Adresssuche
const searchResultSource = new Vector();
const searchResultLayer = new VectorLayer({
source: searchResultSource
});
searchResultLayer.setStyle(new Style({
image: new Circle({
fill: new Fill({
color: 'rgba(0, 128, 0, 1)'
}),
stroke: new Stroke({
color: '#000000',
width: 1.25
}),
radius: 15
})
}));
var element = document.getElementById('search');
element.addEventListener('keydown', listenerFunction);
function listenerFunction(event) {
console.log(event);
console.log(event.keyCode);
if (event.keyCode === 13) {
const xhr = new XMLHttpRequest;
xhr.open('GET', 'https://photon.komoot.de/api/?q=' + element.value + '&limit=3');
xhr.onload = function () {
const json = JSON.parse(xhr.responseText);
const geoJsonReader = new GeoJSON({
featureProjection: 'EPSG:3857'
});
searchResultSource.clear();
const features = geoJsonReader.readFeatures(json);
console.log(features);
searchResultSource.addFeatures(features);
if (!searchResultSource.isEmpty()) {
map.getView().fit(searchResultSource.getExtent(), {
maxZoom: 18,
duration: 500
});
}
};
xhr.send();

}
}
//OpenStreetMap
const OSMbaseLayer = new TileLayer({
type: 'base',
source: new OSM()
});
// Statellit
const satellitLayer = new TileLayer({
source: new XYZ({
attributions: ['Powered by Esri', 'Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community'],
attributionsCollapsible: false,
url: 'https://services.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer/tile/{z}/{y}/{x}',
maxZoom: 30
})
});
//shape
const dachLayer = new VectorLayer({
source: new Vector({
name: 'dach',
url: 'data/dach.geojson',
format: new GeoJSON()
})
});
dachLayer.setStyle(new Style({
fill: new Fill({
color: 'brown'
}),
stroke: new Stroke({
color: 'brown',
width: 0.25
}),
}));
// Layer hinzufügen
map.addLayer(OSMbaseLayer);
map.addLayer(searchResultLayer);
dachLayer.setZIndex(15);
// dach layer anzeigen
const dach = document.getElementById('dach');
dach.addEventListener('click', function (event) {
var checkBox = document.getElementById("dach");
if (checkBox.checked == true) {
dachLayer.setMap(map);
//hitzeLayer.setVisible(true);
} else {
//hitzeLayer.setVisible(false);
dachLayer.setMap(undefined);
}
}); 
// Get the OSMbase Base-Button
const OSMbase = document.getElementById('OSMbase');
OSMbase.addEventListener('click', function (event) {
//contr.style.color = 'ffffff';
//Andere Layer entfernen
map.removeLayer(satellitLayer);
map.removeLayer(searchResultLayer);
//OSM Layer hinzufügen
map.addLayer(OSMbaseLayer);
map.addLayer(searchResultLayer);
});
// Get the satellit Base-Button
const satellit = document.getElementById('satellit');
satellit.addEventListener('click', function (event) {
//Andere Layer entfernen
map.removeLayer(OSMbaseLayer);
map.removeLayer(searchResultLayer);
//Satelliten Layer hinzufügen
map.addLayer(satellitLayer);
map.addLayer(searchResultLayer);
});

Answer 1

getZoom()方法派生自 View 模块：

https://openlayers.org/en/latest/apidoc/module-ol_View-View.html#getZoom

以下作品：

dach.addEventListener('click', function (event) {
var checkBox = document.getElementById("dach");
if (checkBox.checked == true) {
if (map.getview().getZoom() > 17) {
dachLayer.setMap(map);
//hitzeLayer.setVisible(true);
}
} else {
//hitzeLayer.setVisible(false);
dachLayer.setMap(undefined);
}
}); 

同时，您可能希望查看地图上的"moveend"事件以侦听缩放更改，而不是单击：

map.on('moveend', () => {
// do kewl things
}