如何从异步 php db 搜索向地理编码器发送地址
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【中文标题】如何从异步 php db 搜索向地理编码器发送地址【英文标题】：How to send address to geocoder from async php db search 【发布时间】：2019-06-16 07:24:12 【问题描述】：我正在尝试让我的谷歌地图应用程序等待来自使用 php 的 db 调用的 ajax 调用的答案。我知道我需要使用回调，但我不确定在这种情况下如何实现它们，因为 geocoder api 也是异步的。
我尝试了 How to pass variables and data from PHP to javascript? 和 Using gettext with Javascript from PHP via XMLHttpRequest 的回答，但我不确定如何编辑它以适应我的情况。
db.php
$mysqli = new mysqli("host", "user", "pass", "db");
(perform query)...
echo json_encode($result_assoc_array);
location.php
<html>
(html boilerplate)...
<body>
<div id="map"></div>
<script>
var map;
var homeAddress;
var oReq = new XMLHttpRequest();
oReq.onload = function()
homeAddress = JSON.parse(this.responseText).address; //main field I want is address
;
oReq.open("get", "db.php", true);
oReq.send();
function initMap()
map = new google.maps.Map(document.getElementById('map'),
center: lat: -34.397, lng: 150.644 ,
zoom: 15,
);
var bounds = new google.maps.LatLngBounds();
var geocoder = new google.maps.Geocoder();
var markers = [];
geocoder.geocode(
'address': JSON.stringify(homeAddress)
, function(results, status)
if (status == google.maps.GeocoderStatus.OK)
console.log(results);
map.setCenter(results[0].geometry.location);
var marker = new google.maps.Marker(
map: map,
position: results[0].geometry.location
);
bounds.extend(marker.position);
markers.push(marker);
else
alert("Geocode was not successful for the following reason: " + status);
);
(more logic)
</script>
<script src="https://maps.googleapis.com/maps/api/js?key=myKey&callback=initMap&libraries=geometry" async defer></script>
</body>
</html>
这应该给我一张地图，其标记以来自 db 的地址为中心，但我得到的是Geocode was not successful for the following reason: INVALID_REQUEST，因为homeAddress 是undefined。
【问题讨论】：
【参考方案1】：将ajax请求放入initMap，地址可用时在其回调函数中调用geocoder：
function initMap()
map = new google.maps.Map(document.getElementById('map'),
center: lat: -34.397, lng: 150.644 ,
zoom: 15,
);
var bounds = new google.maps.LatLngBounds();
var geocoder = new google.maps.Geocoder();
var markers = [];
var oReq = new XMLHttpRequest();
oReq.onload = function()
homeAddress = JSON.parse(this.responseText).address; //main field I want is address
geocoder.geocode(
'address': JSON.stringify(homeAddress)
, function(results, status)
if (status == google.maps.GeocoderStatus.OK)
console.log(results);
map.setCenter(results[0].geometry.location);
var marker = new google.maps.Marker(
map: map,
position: results[0].geometry.location
);
bounds.extend(marker.position);
markers.push(marker);
else
alert("Geocode was not successful for the following reason: " + status);
);
;
oReq.open("get", "db.php", true);
oReq.send();
(more logic)
【讨论】：
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