我想隐藏并显示Google地图圈。希望API提供了任何简单的方法，但我无法弄明白。
任何人都可以告诉我如何将圆圈放在地图的左角？
等待你的帮助，这是我的代码：
/**
* A distance widget that will display a circle that can be resized and will
* provide the radius in km.
*
* @param {google.maps.Map} map The map to attach to.
*
* @constructor
*/
function DistanceWidget(map) {
this.set('map', map);
this.set('position', map.getCenter());
var marker = new google.maps.Marker({
draggable: true,
title: 'Move me!'
});
// Bind the marker map property to the DistanceWidget map property
marker.bindTo('map', this);
// Bind the marker position property to the DistanceWidget position
// property
marker.bindTo('position', this);
// Create a new radius widget
var radiusWidget = new RadiusWidget();
// Bind the radiusWidget map to the DistanceWidget map
radiusWidget.bindTo('map', this);
// Bind the radiusWidget center to the DistanceWidget position
radiusWidget.bindTo('center', this, 'position');
// Bind to the radiusWidgets' distance property
this.bindTo('distance', radiusWidget);
// Bind to the radiusWidgets' bounds property
this.bindTo('bounds', radiusWidget);
}
DistanceWidget.prototype = new google.maps.MVCObject();
/**
* A radius widget that add a circle to a map and centers on a marker.
*
* @constructor
*/
function RadiusWidget() {
var circle = new google.maps.Circle({
strokeWeight: 2
});
// Set the distance property value, default to 50km.
this.set('distance', 50);
// Bind the RadiusWidget bounds property to the circle bounds property.
this.bindTo('bounds', circle);
// Bind the circle center to the RadiusWidget center property
circle.bindTo('center', this);
// Bind the circle map to the RadiusWidget map
circle.bindTo('map', this);
// Bind the circle radius property to the RadiusWidget radius property
circle.bindTo('radius', this);
// Add the sizer marker
this.addSizer_();
}
RadiusWidget.prototype = new google.maps.MVCObject();
/**
* Update the radius when the distance has changed.
*/
RadiusWidget.prototype.distance_changed = function () {
this.set('radius', this.get('distance') * 1000);
};
/**
* Add the sizer marker to the map.
*
* @private
*/
RadiusWidget.prototype.addSizer_ = function () {
var sizer = new google.maps.Marker({
draggable: true,
title: 'Drag me!'
});
sizer.bindTo('map', this);
sizer.bindTo('position', this, 'sizer_position');
var me = this;
google.maps.event.addListener(sizer, 'drag', function () {
// Set the circle distance (radius)
me.setDistance();
});
};
/**
* Update the center of the circle and position the sizer back on the line.
*
* Position is bound to the DistanceWidget so this is expected to change when
* the position of the distance widget is changed.
*/
RadiusWidget.prototype.center_changed = function () {
var bounds = this.get('bounds');
// Bounds might not always be set so check that it exists first.
if (bounds) {
var lng = bounds.getNorthEast().lng();
// Put the sizer at center, right on the circle.
var position = new google.maps.LatLng(this.get('center').lat(), lng);
this.set('sizer_position', position);
}
};
/**
* Calculates the distance between two latlng points in km.
* @see http://www.movable-type.co.uk/scripts/latlong.html
*
* @param {google.maps.LatLng} p1 The first lat lng point.
* @param {google.maps.LatLng} p2 The second lat lng point.
* @return {number} The distance between the two points in km.
* @private
*/
RadiusWidget.prototype.distanceBetweenPoints_ = function (p1, p2) {
if (!p1 || !p2) {
return 0;
}
var R = 6371; // Radius of the Earth in km
var dLat = (p2.lat() - p1.lat()) * Math.PI / 180;
var dLon = (p2.lng() - p1.lng()) * Math.PI / 180;
var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) + Math.cos(p1.lat() * Math.PI / 180) * Math.cos(p2.lat() * Math.PI / 180) * Math.sin(dLon / 2) * Math.sin(dLon / 2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
var d = R * c;
return d;
};
/**
* Set the distance of the circle based on the position of the sizer.
*/
RadiusWidget.prototype.setDistance = function () {
// As the sizer is being dragged, its position changes. Because the
// RadiusWidget's sizer_position is bound to the sizer's position, it will
// change as well.
var pos = this.get('sizer_position');
var center = this.get('center');
var distance = this.distanceBetweenPoints_(center, pos);
// Set the distance property for any objects that are bound to it
this.set('distance', distance);
};
function init() {
var mapDiv = document.getElementById('map-canvas');
var map = new google.maps.Map(mapDiv, {
center: new google.maps.LatLng(37.790234970864, -122.39031314844),
zoom: 8,
mapTypeId: google.maps.MapTypeId.ROADMAP
});
var distanceWidget = new DistanceWidget(map);
google.maps.event.addListener(distanceWidget, 'distance_changed', function () {
displayInfo(distanceWidget);
});
google.maps.event.addListener(distanceWidget, 'position_changed', function () {
displayInfo(distanceWidget);
});
}
function displayInfo(widget) {
var info = document.getElementById('info');
info.innerHTML = 'Position: ' + widget.get('position') + ', distance: ' + widget.get('distance');
}
google.maps.event.addDomListener(window, 'load', init);
提前致谢。 Vijay kumar HM
答案 0 :(得分：0)
更改了此代码（将“map”和“distanceWidget”设为全局）：
var map = null;
var distanceWidget = null;
function init() {
var mapDiv = document.getElementById('map-canvas');
map = new google.maps.Map(mapDiv, {
center: new google.maps.LatLng(37.790234970864, -122.39031314844),
zoom: 8,
mapTypeId: google.maps.MapTypeId.ROADMAP
});
distanceWidget = new DistanceWidget(map);
google.maps.event.addListener(distanceWidget, 'distance_changed', function () {
displayInfo(distanceWidget);
});
google.maps.event.addListener(distanceWidget, 'position_changed', function () {
displayInfo(distanceWidget);
});
}
function displayInfo(widget) {
var info = document.getElementById('info');
info.innerHTML = 'Position: ' + widget.get('position') + ', distance: ' + widget.get('distance');
}
将此添加到HTML中，隐藏并显示distanceWidget：
<button onclick="distanceWidget.set('map',null);" >Hide</button>
<button onclick="distanceWidget.set('map',map);">Show</button>
<div id="info"></div>
<div id="map-canvas"></div>