我正在开发一个应用程序,其中包含大件垃圾信号,每个公民都可以向当局告知收集垃圾的地点。
数据(地址和坐标)已存储到 Firebase 中,我正在研究在 Google map 中显示标记。
代码如下:
jQuery(function($) {
// Asynchronously Load the map API
var script = document.createElement('script');
script.src = "//maps.googleapis.com/maps/api/js?&callback=initialize";
document.body.appendChild(script);
});
function initialize() {
var map;
var bounds = new google.maps.LatLngBounds();
var mapOptions = {
mapTypeId: 'roadmap'
};
// Display a map on the page
map = new google.maps.Map(document.getElementById("map_canvas"), mapOptions);
map.setTilt(45);
markers: findMarkers();
console.log(markers);
console.log(markers.length);
// Info Window Content
var infoWindowContent = [
['<div class="info_content">' +
'<p>' + 'adresse' +'</p>' + '</div>'],
];
// Display multiple markers on a map
var infoWindow = new google.maps.InfoWindow(), marker, i;
// Loop through our array of markers & place each one on the map
for( i = 0; i < markers.length; i++ ) {
var position = new google.maps.LatLng(markers[i][1].lat(), markers[i][1].lng());
bounds.extend(position);
marker = new google.maps.Marker({
position: position,
map: map,
title: markers[i][0]
});
// Allow each marker to have an info window
google.maps.event.addListener(marker, 'click', (function(marker, i) {
return function() {
infoWindow.setContent(infoWindowContent[i][0]);
infoWindow.open(map, marker);
}
})(marker, i));
}
var boundsListener = google.maps.event.addListener((map), 'bounds_changed', function(event) {
this.setZoom(14);
google.maps.event.removeListener(boundsListener);
});
}
function findMarkers(){
markers = [];
var data = firebase.database();
var dataRef = firebase.database().ref("signalement/");
dataRef.on("child_added", function(data) {
var key = data.key;
const signalement = data.val();
const adresse = signalement.adresse;
const coordonnees = signalement.coordonnees;
var marker = [adresse, coordonnees];
markers.push( marker );
});
// Multiple Markers
return markers;
}
</script>
</head>
<body>
<div id="map_wrapper">
<div id="map_canvas" class="mapping"></div>
</div>
</html>
问题来自于 console.log(markers.length);
它等于 0!而前面的 console.log(markers);
显示了对象。
也许 var 标记有语法错误? 反正。 有人可以帮我处理这个案子吗?
谢谢
最佳答案
看起来问题出在 firebase 数据回调上。由于您已经为 google map api callback=initialize
设置了回调,因此在执行该函数时,Firebase 中的标记数据尚未准备好。
我宁愿做这样的事情(请记住,Firebase 回调需要比加载的 Google map 脚本更长的时间,并且 map 依赖于 Firebase 中的数据)。
jQuery(function($) {
// Asynchronously Load the map API
var script = document.createElement('script');
script.src = "//maps.googleapis.com/maps/api/js?&callback=findMarkers";
document.body.appendChild(script);
});
function initialize(markers) {
var map;
var bounds = new google.maps.LatLngBounds();
var mapOptions = {
mapTypeId: 'roadmap'
};
// Display a map on the page
map = new google.maps.Map(document.getElementById("map_canvas"), mapOptions);
map.setTilt(45);
console.log(markers);
console.log(markers.length);
// Info Window Content
var infoWindowContent = [
['<div class="info_content">' +
'<p>' + 'adresse' +'</p>' + '</div>'],
];
// Display multiple markers on a map
var infoWindow = new google.maps.InfoWindow(), marker, i;
// Loop through our array of markers & place each one on the map
for( i = 0; i < markers.length; i++ ) {
var position = new google.maps.LatLng(markers[i][1].lat(), markers[i][1].lng());
bounds.extend(position);
marker = new google.maps.Marker({
position: position,
map: map,
title: markers[i][0]
});
// Allow each marker to have an info window
google.maps.event.addListener(marker, 'click', (function(marker, i) {
return function() {
infoWindow.setContent(infoWindowContent[i][0]);
infoWindow.open(map, marker);
}
})(marker, i));
}
var boundsListener = google.maps.event.addListener((map), 'bounds_changed', function(event) {
this.setZoom(14);
google.maps.event.removeListener(boundsListener);
});
}
function findMarkers(){
markers = [];
var data = firebase.database();
var dataRef = firebase.database().ref("signalement/");
dataRef.on("child_added", function(data) {
var key = data.key;
const signalement = data.val();
const adresse = signalement.adresse;
const coordonnees = signalement.coordonnees;
var marker = [adresse, coordonnees];
markers.push( marker );
});
// send prepared marker array to map initialize function
intialize(markers);
}
关于javascript - Firebase 和 Google map - 读取数据集并创建标记。如何读取对象?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/44508045/