切換Google地圖圈隱藏和取消隱藏

Question

我想隱藏並顯示Google地圖圈。希望API提供了任何簡單的方法，但我無法弄清楚。

而且任何人都可以讓我知道如何將圓圈放置在地圖的左上角？

等待您的幫助，這是我的代碼：

/** 
* 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); 

在此先感謝。 維賈伊·庫馬爾HM

Answer 1

改變了這種代碼（由 「地圖」 和 「distanceWidget」 全球）：

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'); 
} 

已將此添加到HTML，隱藏和顯示的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> 

working fiddle