center map with multiple markers in Google Maps API v3
This is what I use to display a map with 3 pins/markers:
<script>
function initialize() {
var locations = [
['DESCRIPTION', 41.926979, 12.517385, 3],
['DESCRIPTION', 41.914873, 12.506486, 2],
['DESCRIPTION', 41.918574, 12.507201, 1]
];
var map = new google.maps.Map(document.getElementById('map'), {
zoom: 15,
center: new google.maps.LatLng(41.923, 12.513),
mapTypeId: google.maps.MapTypeId.ROADMAP
});
var infowindow = new google.maps.InfoWindow();
var marker, i;
for (i = 0; i < locations.length; i++) {
marker = new google.maps.Marker({
position: new google.maps.LatLng(locations[i][1], locations[i][2]),
map: map
});
google.maps.event.addListener(marker, 'click', (function(marker, i) {
return function() {
infowindow.setContent(locations[i][0]);
infowindow.open(map, marker);
}
})(marker, i));
}
}
function loadScript() {
var script = document.createElement('script');
script.type = 'text/javascript';
script.src = 'https://maps.googleapis.com/maps/api/js?v=3.exp&sensor=false&' + 'callback=initialize';
document.body.appendChild(script);
}
window.onload = loadScript;
</script>
<div id="map" style="width: 900px; height: 700px;"></div>
What I'm looking for is a way to avoid having to “manually” find the center of the map with center: new google.maps.LatLng(41.923, 12.513) . Is there a way to automatically have the map centered on the three coordinates?
There's an easier way, by extending an empty LatLngBounds rather than creating one explicitly from two points. (See this question for more details)
Should look something like this, added to your code:
//create empty LatLngBounds object
var bounds = new google.maps.LatLngBounds();
var infowindow = new google.maps.InfoWindow();
for (i = 0; i < locations.length; i++) {
var marker = new google.maps.Marker({
position: new google.maps.LatLng(locations[i][1], locations[i][2]),
map: map
});
//extend the bounds to include each marker's position
bounds.extend(marker.position);
google.maps.event.addListener(marker, 'click', (function(marker, i) {
return function() {
infowindow.setContent(locations[i][0]);
infowindow.open(map, marker);
}
})(marker, i));
}
//now fit the map to the newly inclusive bounds
map.fitBounds(bounds);
//(optional) restore the zoom level after the map is done scaling
var listener = google.maps.event.addListener(map, "idle", function () {
map.setZoom(3);
google.maps.event.removeListener(listener);
});
This way, you can use an arbitrary number of points, and don't need to know the order beforehand.
Demo jsFiddle here: http://jsfiddle.net/x5R63/
我认为你必须计算纬度经度min和经度min：下面是一个例子，用这个函数来定位你的观点：
//Example values of min & max latlng values
var lat_min = 1.3049337;
var lat_max = 1.3053515;
var lng_min = 103.2103116;
var lng_max = 103.8400188;
map.setCenter(new google.maps.LatLng(
((lat_max + lat_min) / 2.0),
((lng_max + lng_min) / 2.0)
));
map.fitBounds(new google.maps.LatLngBounds(
//bottom left
new google.maps.LatLng(lat_min, lng_min),
//top right
new google.maps.LatLng(lat_max, lng_max)
));
To find the exact center of the map you'll need to translate the lat/lon coordinates into pixel coordinates and then find the pixel center and convert that back into lat/lon coordinates.
You might not notice or mind the drift depending how far north or south of the equator you are. You can see the drift by doing map.setCenter(map.getBounds().getCenter()) inside of a setInterval, the drift will slowly disappear as it approaches the equator.
You can use the following to translate between lat/lon and pixel coordinates. The pixel coordinates are based on a plane of the entire world fully zoomed in, but you can then find the center of that and switch it back into lat/lon.
var HALF_WORLD_CIRCUMFERENCE = 268435456; // in pixels at zoom level 21
var WORLD_RADIUS = HALF_WORLD_CIRCUMFERENCE / Math.PI;
function _latToY ( lat ) {
var sinLat = Math.sin( _toRadians( lat ) );
return HALF_WORLD_CIRCUMFERENCE - WORLD_RADIUS * Math.log( ( 1 + sinLat ) / ( 1 - sinLat ) ) / 2;
}
function _lonToX ( lon ) {
return HALF_WORLD_CIRCUMFERENCE + WORLD_RADIUS * _toRadians( lon );
}
function _xToLon ( x ) {
return _toDegrees( ( x - HALF_WORLD_CIRCUMFERENCE ) / WORLD_RADIUS );
}
function _yToLat ( y ) {
return _toDegrees( Math.PI / 2 - 2 * Math.atan( Math.exp( ( y - HALF_WORLD_CIRCUMFERENCE ) / WORLD_RADIUS ) ) );
}
function _toRadians ( degrees ) {
return degrees * Math.PI / 180;
}
function _toDegrees ( radians ) {
return radians * 180 / Math.PI;
}