多个多边形 MySQL答案

【问题标题】：Multiple Polygons MySQL多个多边形 MySQL
【发布时间】：2012-05-29 23:36:22
【问题描述】：

我正在尝试从数据库中绘制几个单独的多边形（建筑物）。我从数据库中获取的数据如下所示：

<buildings>
    <building build_id="94" build_gebaeude="A"
        build_geoX="49.26173942769648" build_geoY="7.350542675857582"
    />
    <building build_id="95" build_gebaeude="A"
        build_geoX="49.26173942769648" build_geoY="7.3524094933319475"
    />
    <building build_id="96" build_gebaeude="A"
        build_geoX="49.26019903253632" build_geoY="7.35234512031559"
    />
    <building build_id="97" build_gebaeude="A"
        build_geoX="49.26032506667364" build_geoY="7.350692879562416"
    />
    <building build_id="98" build_gebaeude="B"
        build_geoX="49.26155738350112" build_geoY="7.362129818801918"
    />
    <building build_id="99" build_gebaeude="B"
        build_geoX="49.26157138692462" build_geoY="7.364275586013832"
    />
    <building build_id="100" build_gebaeude="B"
        build_geoX="49.260255047748224" build_geoY="7.364361416702309"
    />
    <building build_id="101" build_gebaeude="B"
        build_geoX="49.260311062896506" build_geoY="7.362065445785561"
    />
</buildings>

以下代码显示了我在绘制建筑物时所做的工作：

for (var i = 0; i < building.length-1; i++) {
    var point = new google.maps.LatLng(
        parseFloat(building[i].getAttribute("build_geoX")),
        parseFloat(building[i].getAttribute("build_geoY"))
    );

    latlngbounds.extend(point);

    if( building[i].getAttribute("build_gebaeude") == 
        building[i+1].getAttribute("build_gebaeude") )
    {
        path.push(point);
    }
    else {
        path.push(point);
        poly = new google.maps.Polygon({
            paths: path,
            strokeWeight: 5,
            strokeOpacity: 1,
            fillOpacity: 0.30,
            strokeColor:'#FFFFFF',
            fillColor: '#a3141d'
        }); 
        polygons.push(poly);
        path.clear();
    }
}   
polygons[0].setMap(map);
polygons[1].setMap(map);

问题是不是所有的点都画出来了？我不明白问题出在哪里？

【问题讨论】：

标签： google-maps-api-3

【解决方案1】：

paths 数组似乎有问题。从您包含的代码中不清楚 paths 是 JavaScript Array 还是类似数组的对象，但由于您在 for 循环中使用 paths 然后尝试清除 paths在循环内，我建议：

根据需要在循环内创建一个新的pathsArray
添加代码来管理数组循环的状态
更改用于检查建筑属性和测试相等性的代码
由于您将路径数组传递给 Polygon 构造函数，因此不要清除该数组

var paths = null;
var aNewPathIsNeeded = true;
for ( var i = 0; i < building.length-1; i++) {
    //Create your point
    //Extend your bounds
    //Since you always add the point to the paths array, move it out of the if
    //check and perform some array state management:

    if ( aNewPathIsNeeded ) {
        paths = new Array( point );
        aNewPathIsNeeded = false;
    }
    else { paths.push( point ); }

    //Change the if condition to deal with just the specific case of interest:

    var currentBldgAttr = building[i].getAttribute("build_gebaeude");
    var nextBldgAttr = building[i+1].getAttribute("build_gebaeude");
    if ( !( currentBldgAttr === nextBldgAttr ) ) { //Change to use: '==='
        //Create your polygon
        //Add the polygon to the polygons array
        //New code to manage paths state:
        aNewPathIsNeeded = true;
    }
}

我不确定您的问题到底是什么，但我相信这段代码将帮助您继续前进。作为旁注，clear() 不是 JavaScript Array 方法；当您想清空Array 时，请使用：array.length = 0，如下所述：Is JavaScript's array.clear() not a function?

【讨论】：