我正在某个国家/地区的谷歌地图中加载数据图层(它是一个国家/地区的图纸):
gem install
我很确定没有,但是......我有一种方法可以检查地图的边界是否在数据层的范围内?
(基本上,我想知道,当用户在地图上导航时,如果当前视口位于数据层内);
map.data.addGeoJson(geoJsonObject);
也许我可以在西南边界的位置查询数据层并检查一些道具。表明我在那个数据层内?
或者至少:
有没有人知道如何以编程方式获取某个特征对象,知道lat和long?
此处谷歌地图使用事件来访问要素对象:
var bounds = this.map.getBounds();
var sw = bounds.getSouthWest();
但我不想使用事件。 是否有方法提供点的坐标并获取要素对象? 类似的东西:
map.data.addListener('click', function(event) {
event.feature.setProperty('isColorful', true);
});
答案 0 :(得分:4)
google.maps.LatLngBounds.contains
函数可用于此目的,但由于它接受单个位置,因此建议使用以下解决方案:
1)从GeoJSON坐标初始化数据层边界:
var dataLayer = map.data;
var layerBounds = new google.maps.LatLngBounds();
//1.collect all coordinates from data layer
dataLayer.forEach(function(f) {
var geometry = f.getGeometry();
processCoordinates(geometry, layerBounds.extend, layerBounds);
});
2)确定地图边界是否在图层边界内:
if (layerBounds.contains(map.getBounds().getNorthEast()) && layerBounds.contains(map.getBounds().getSouthWest())) {
//...
}
工作示例
在提供的示例中,如果是地图,将显示绿色区域 边界在图层边界内,红色在 相反的情况:
var area;
function initMap() {
var map = new google.maps.Map(document.getElementById('map'), {
center: {
lat: 53.349248,
lng: -6.255323
},
zoom: 6,
mapTypeId: google.maps.MapTypeId.TERRAIN
});
displayDataLayer(map);
document.getElementById("btnShow").onclick = function() {
var result = displayDataLayerBoundsArea(map);
};
}
function displayDataLayer(map) {
var dataLayer = map.data;
dataLayer.loadGeoJson('https://gist.githubusercontent.com/vgrem/440708612b574764c309/raw/2a4e2feadc204806440c51a14c2ef1f54f4fc3d8/Census2011_Province_generalised20m.json');
dataLayer.setMap(map);
}
function displayDataLayerBoundsArea(map) {
var dataLayer = map.data;
var layerBounds = new google.maps.LatLngBounds();
//1.collect all coordinates from data layer
dataLayer.forEach(function(f) {
var geometry = f.getGeometry();
processCoordinates(geometry, layerBounds.extend, layerBounds);
});
if (area != null) {
area.setMap(null);
}
//2.determine whether map bounds are contained within a layer bounds
if (layerBounds.contains(map.getBounds().getNorthEast()) && layerBounds.contains(map.getBounds().getSouthWest())) {
//map.fitBounds(bounds);
area = new google.maps.Rectangle({
strokeColor: '#00FF00',
strokeOpacity: 0.8,
strokeWeight: 2,
fillColor: '#00FF00',
fillOpacity: 0.35,
map: map,
bounds: {
north: layerBounds.getNorthEast().lat(),
south: layerBounds.getSouthWest().lat(),
east: layerBounds.getNorthEast().lng(),
west: layerBounds.getSouthWest().lng()
}
});
} else {
//map.fitBounds(bounds);
area = new google.maps.Rectangle({
strokeColor: '#FF0000',
strokeOpacity: 0.8,
strokeWeight: 2,
fillColor: '#FF0000',
fillOpacity: 0.35,
map: map,
bounds: {
north: layerBounds.getNorthEast().lat(),
south: layerBounds.getSouthWest().lat(),
east: layerBounds.getNorthEast().lng(),
west: layerBounds.getSouthWest().lng()
}
});
}
}
function processCoordinates(geometry, callback, thisArg) {
if (geometry instanceof google.maps.LatLng) {
callback.call(thisArg, geometry);
} else if (geometry instanceof google.maps.Data.Point) {
callback.call(thisArg, geometry.get());
} else {
geometry.getArray().forEach(function(g) {
processCoordinates(g, callback, thisArg);
});
}
}

#map {
width: 800px;
height: 640px;
}

<button id="btnShow">Show</button>
<div id="map"></div>
<script async defer src="https://maps.googleapis.com/maps/api/js?callback=initMap"></script>
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