如何只使用DOM对象获取leaflet.js实例？

Question

我现在正在构建一个自定义的Knockout.js绑定来处理多边形的绘制.在这种情况下,Knockout API只给我一个DOM对象的引用来访问我需要更新的内容.但是,看起来像设计leaflet.js希望用户将map实例存储在它们的实现中.我没有这个选择.

尝试这个给了我一个错误: var existingMap = L.map('aMapIDGoesHere')

错误是:map already initialized.

我可以用任何方式使用DOM元素或元素ID来访问地图实例吗？

根据请求这里是自定义绑定,请注意它是一项正在进行的工作:

ko.bindingHandlers.leafletDraw = {
  init: function(element, valueAccessor, allBindingsAccessor) {
    var map = L.map(element).setView([40, -90], 3);
    var tiles = L.tileLayer('http://{s}.tile.osm.org/{z}/{x}/{y}.png', {
        attribution: 'OSM',
        minZoom: 2
    }).addTo(map);

    // Initialise the FeatureGroup to store editable layers
    var editableLayers = new L.FeatureGroup();
    map.addLayer(editableLayers);

    // Initialise the draw control and pass it the FeatureGroup of editable layers
    var drawOptions = {
      edit: {
        featureGroup: editableLayers,
        remove: false
      },
      draw: {
        polyline: false,
        circle: false,
        marker: false,
        polygon: {
          allowIntersection: false,
          showArea: true
        }
      }
    }
    var drawControl = new L.Control.Draw(drawOptions);
    map.addControl(drawControl);

    // when a shape is first created
    map.on('draw:created', function (e) {
      var shapeString = $.map(e.layer._latlngs, function(pair) { return pair.lng.toString()+"::"+pair.lat.toString(); }).join(";;;");
      var value = valueAccessor();
      if (ko.isObservable(value)) {
        value(shapeString);
      }

      editableLayers.addLayer(e.layer);

      drawControl.removeFrom(map);
      drawOptions.draw.polygon = false;
      drawOptions.draw.rectangle = false;
      var editControl = new L.Control.Draw(drawOptions);
      map.addControl(editControl);
    });

    // handle when a shape is edited
    map.on('draw:edited', function (e) {
      var editedLayer = e.layers._layers[Object.keys(e.layers._layers)[0]];
      var shapeString = $.map(editedLayer._latlngs, function(pair) { return pair.lng.toString()+"::"+pair.lat.toString(); }).join(";;;");
      var value = valueAccessor();
      if (ko.isObservable(value)) {
        value(shapeString);
      }
    });
  },
  update: function(element, valueAccessor) {
    // need to figure this out since we can't access leaflet params from 
  }
};

特别注意您会注意到我将点转换为串联字符串.这暂时是必要的.

Answer 1

只要您确定不会删除DOM元素,您只需将其添加为DOM元素本身的子属性即可.这是一个绑定处理程序,使用传单首页上的代码来设置传单映射:

ko.bindingHandlers.leaflet = {
    init: function(element, valueAccessor){
        var map = L.map(element);
        element.myMapProperty = map;
        L.tileLayer('http://{s}.tile.osm.org/{z}/{x}/{y}.png', {
            attribution: '&copy; <a href="http://osm.org/copyright">OpenStreetMap</a> contributors'
        }).addTo(map);
    },
    update: function(element, valueAccessor){
        var existingMap = element.myMapProperty;
        var value = ko.unwrap(valueAccessor());
        var latitude = ko.unwrap(value.latitude);
        var longitude = ko.unwrap(value.longitude);
        var zoom = ko.unwrap(value.zoom);
        existingMap.setView([latitude, longitude], zoom);
    }
};

要使用绑定处理程序,您只需绑定如下:

<div data-bind="leaflet: { latitude: latitudeProperty, longitude: longitudeProperty, zoom: zoomProperty }"></div>

只需确保您还div确保它具有高度和宽度.我写了一个jsfiddle,它使用上面的leaflet bindingHandler你可以尝试一下.

我只在Internet Explorer 11,Firefox 26.0和Firefox 27.0.1中测试了这个jsfiddle.