监听器事件总是触发最后一个元素的信息

Question

我正在尝试制作基于地图的应用程序,但我遇到了一些困难.我一直在使用的原始代码为每个标记添加了一个单独的InfoWindow,但我想使用单个InfoWindow来获取它,我可以动态设置内容.

但是,我似乎仍然对JavaScript的行为有点模糊,因为每次点击任何标记时,InfoWindow会弹出最后一个标记,并且警报会指示最后一个条目的ID locations.

短片,问题突出显示:

function plotLocations(my_locations) {
    locations = my_locations;
    for(var i=0; i<locations.length; i++) {
        var pos = new google.maps.LatLng(locations[i].loc_lat, locations[i].loc_lng);
        var icon = new google.maps.MarkerImage(
            "http://goo.gl/TQpwU",
            new google.maps.Size(20,32),
            new google.maps.Point(0,0),
            new google.maps.Point(0,32)
        );
        var marker = new google.maps.Marker({
            map: map,
            position: pos,
            animation: google.maps.Animation.DROP,
            icon: icon
        });
// ! -- trouble right here -- ! //
        google.maps.event.addListener(marker, 'click', function() {
            setPopInfo(pos, i);
        });
// ! -- ------------------ -- ! //
    }
}

function setPopInfo(pos, index) {
    pop_info.setPosition(pos);
    pop_info.open(map);
    window.alert(pos+"::"+index);
}

我剩下的大部分代码:

var map;
var mapBounds;
var locations;
var pop_info;

$(document).ready(init);

function init() {
    var mapOptions = {
        mapTypeId: google.maps.MapTypeId.ROADMAP
    };
    map = new google.maps.Map(document.getElementById('map_canvas'), mapOptions);
    pop_info = new google.maps.InfoWindow({
        content: "I'm not populated!",
        size: new google.maps.Size(100,25)
    });
    google.maps.event.addListener(map, 'bounds_changed', function() {
        queryLocations(map.getBounds());
    });

    prepareGeolocation();
    doGeolocation();
}

function queryLocations(bounds) {
    jQuery.ajax({
        url: 'http://mydomain.com/myapp/test2.php',
        data: bounds.toString(),
        dataType: 'json',
        success: addLocations
    });
}

function addLocations(new_locations) {
    document.getElementById('footer').innerHTML = new_locations;
    plotLocations(new_locations);
}

我对单个InfoWindow的推理是,一旦创建了几百个Markers和InfoWindows,性能可能会急转直下.我正在努力做到可行/可取吗？

Answer 1

出现此问题是因为您在循环内定义了事件侦听器回调函数.闭包动态地引用它们的上下文,而不是在定义时绑定到数据的副本,因此您有效地创建了locations.length多个函数,这些函数都绑定到相同的值marker,pos并且i,这些是它们在循环终止.

为了解决这个问题,你可以创建一个addListener在循环体外调用的函数,如下所示:

function plotLocations (my_locations) {
    locations = my_locations;
    for(var i=0; i<locations.length; i++) {
        var pos = new google.maps.LatLng(locations[i].loc_lat, locations[i].loc_lng);
        var icon = new google.maps.MarkerImage(
            "http://goo.gl/TQpwU",
            new google.maps.Size(20,32),
            new google.maps.Point(0,0),
            new google.maps.Point(0,32)
        );
        var marker = new google.maps.Marker({
            map: map,
            position: pos,
            animation: google.maps.Animation.DROP,
            icon: icon
        });
        bindEvent(marker, pos, i);
    }
}

function bindEvent (marker, pos, i) {
    google.maps.event.addListener(marker, 'click', function() {
        setPopInfo(pos, i);
    });
}