Method addLabelLayer

src/openlayers/mapping/WebMap.js:3285–3316

* @private * @function WebMap.prototype.addLabelLayer * @description 添加标签图层 * @param {Object} layerInfo - 图层信息 * @param {Array} features -feature的集合 * @returns {ol.layer.Vector} 图层对象

(layerInfo, features)

   * @returns {ol.layer.Vector} 图层对象
   */
  addLabelLayer(layerInfo, features) {
    let labelStyle = layerInfo.labelStyle;
    let style = this.getLabelStyle(labelStyle, layerInfo);
    let layer = (layerInfo.labelLayer = new olLayer.Vector({
      declutter: true,
      styleOL: style,
      labelField: labelStyle.labelField,
      source: new Vector({
        features: features,
        wrapX: false
      })
    }));
    layer.setStyle((features) => {
      let labelField = labelStyle.labelField;
      let label = features.get('attributes')[labelField.trim()] + '';
      if (label === 'undefined') {
        return null;
      }
      let styleOL = layer.get('styleOL');
      let text = styleOL.getText();
      if (text && text.setText) {
        text.setText(label);
      }
      return styleOL;
    });
    this.map.addLayer(layer);
    layer.setVisible(layerInfo.visible);
    layer.setZIndex(1000);
    const { visibleScale } = layerInfo;
    visibleScale && this.setVisibleScales(layer, visibleScale);
    return layer;
  }

  /**
   * @private