使用 javascript 过滤要素布局 ArcGis 时如何显示结果计数

Question

我在 object 中定义的一个项目中有多个布局，如下所示：

const layersByYears = [ 
    { year: 1918, layers: [ 
        { layerID: "443709212b894e9297888b3194b51100", opacity: 1.0, name: "ORP", featureLayer: null },
        { layerID: "61a605dca69c4aa0ac1b3858ba328fd3", opacity: 1.0, name: "obceSouc", featureLayer: null }
    ] },
    { year: 1936, layers: [ 
        { layerID: "a2e007238e304f1ea58005fc69c921e9", opacity: 1.0, name: "ORP", featureLayer: null },
        { layerID: "61a605dca69c4aa0ac1b3858ba328fd3", opacity: 1.0, name: "obceSouc", featureLayer: null }
    ] },
    { year: 1950, layers: [ 
        { layerID: "23bcd52310854d6185e5f22a4eca0303", opacity: 1.0, name: "ORP", featureLayer: null },
        { layerID: "61a605dca69c4aa0ac1b3858ba328fd3", opacity: 1.0, name: "obceSouc", featureLayer: null }
    ] },
    { year: 1981, layers: [ 
        { layerID: "401e9530ba074936800a8f596fc49d70", opacity: 1.0, name: "ORP", featureLayer: null },
        { layerID: "61a605dca69c4aa0ac1b3858ba328fd3", opacity: 1.0, name: "obceSouc", featureLayer: null }
    ] },    
]

然后我创建变量来设置所有层：

const createFL = (layer) => {
        if(layer.featureLayer !== null && layer.featureLayer !== undefined)
            return;

        layer.featureLayer = new FeatureLayer({ portalItem: {
            id: layer.layerID,
            opacity: layer.opacity !== undefined ? layer.opacity : 1.0,
            visible: false,
        } })

        layer.featureLayer.load().then(function() {
            $("loadingProgressbar").value = ++loadingProgress.value;
            $("loadingProgressbar").max = loadingProgress.max;
            if(loadingProgress.max === loadingProgress.value)
                $("loadingProgressbar").style.display = "none";
        });
    }

最后我提供这样的过滤器：

function doQuery() {
    var selModul = document.getElementById("jevSelect");
    var attributeName = selModul.options[selModul.selectedIndex].value;
    

    const expressionSign = document.getElementById("signSelect");
    
    var selJev = document.getElementById("jevSelect");
    var inputValue = selJev.options[selJev.selectedIndex].text;

    let expression;
        
    expression = `${attributeName}${expressionSign.value}'${inputValue}'`;
        document.getElementById("printResults").innerHTML = expression;

        layersByYears.forEach(layerByYear =>
            layerByYear.layers.forEach(layer => {
                layer.featureLayer.definitionExpression = expression;   
            })
        )
        
    }

我需要的是在 map 的点上将每个过滤器上的结果计数（数字）显示为 label。 项目在这里map 项目- 问题是在 1936 年。

Answer 1

如果您想要符合条件的要素计数，您可以仅使用计数查询，例如FeatureLayer的queryFeatureCount方法（ ArcGIS JS API - FeatureLayer ）。 在您的情况下，您可以在结构中添加一个额外的属性，例如count并在每次更改定义表达式时填充它，如下所示，

const layerQueryFeatureCount = function (layer, where) {
    if (!where) {
        where = "1==1";
    }
    layer.featureLayer.queryFeatureCount(new Query({where})).then(
        function (results) {
            layer.count = results;
            console.log(`${layer.name}: ${where} (count=${results})`);
        }, function (error) {
            console.log(error);
            layer.count = "-";
            console.log(`${layer.name}: ${where} (count=${error})`);
        }
    );
}