制作分级统计图

分级统计图是一种主题地图，其中行政区的颜色或阴影是根据数据值确定的。您可以使用样式工厂函数根据数据设置地图样式，数据集中的每个行政区都与一系列数值相关联。以下示例地图显示了 美国各州的分级统计图。

在此示例中，数据包含该州的地点 ID。样式工厂函数会根据相应状态的地点 ID 的经过哈希处理的值，有条件地为每个状态着色。

1. 按照 开始 以创建新的地图 ID 和地图样式。请务必启用 行政区级别 1 的地图项图层。

2. 在地图初始化时获取对行政区第 1 级地图项图层的引用。在美国，这类行政级别 与各个州相对应

   Java

   private FeatureLayer areaLevel1Layer;
   
   @Override
   public void onMapReady(GoogleMap map) {
     areaLevel1Layer = map.getFeatureLayer(new FeatureLayerOptions.Builder()
       .featureType(FeatureType.ADMINISTRATIVE_AREA_LEVEL_1)
       .build());
   
     // Apply style factory function to ADMINISTRATIVE_AREA_LEVEL_1 layer.
     styleAreaLevel1Layer();
   }

   Kotlin

   private var areaLevel1Layer: FeatureLayer? = null
   
   override fun onMapReady(googleMap: GoogleMap) {
     // Get the ADMINISTRATIVE_AREA_LEVEL_1 feature layer.
     areaLevel1Layer = googleMap.getFeatureLayer(FeatureLayerOptions.Builder()
       .featureType(FeatureType.ADMINISTRATIVE_AREA_LEVEL_1)
       .build())
   
     // Apply style factory function to ADMINISTRATIVE_AREA_LEVEL_1 layer.
     styleAreaLevel1Layer()
   }

3. 创建一个样式工厂函数，并将其应用于 行政区级别 1 的地图项图层。以下示例将 函数设置为表示美国各州的多边形。

   Java

   private void styleAreaLevel1Layer() {
     FeatureLayer.StyleFactory styleFactory = (Feature feature) -> {
       if (feature instanceof PlaceFeature) {
         PlaceFeature placeFeature = (PlaceFeature) feature;
   
         // Return a hueColor in the range [-299,299]. If the value is
         // negative, add 300 to make the value positive.
         int hueColor = placeFeature.getPlaceId().hashCode() % 300;
         if (hueColor < 0) {
           hueColor += 300;
         }
   
         return new FeatureStyle.Builder()
           // Set the fill color for the state based on the hashed hue color.
           .fillColor(Color.HSVToColor(150, new float[] {hueColor, 1, 1}))
           .build();
       }
       return null;
     };
   
     // Apply the style factory function to the feature layer.
     areaLevel1Layer.setFeatureStyle(styleFactory);
   }

   Kotlin

   private fun styleAreaLevel1Layer() {
     val styleFactory = FeatureLayer.StyleFactory { feature: Feature ->
         if (feature is PlaceFeature) {
             val placeFeature: PlaceFeature = feature as PlaceFeature
   
             // Return a hueColor in the range [-299,299]. If the value is
             // negative, add 300 to make the value positive.
             var hueColor: Int = placeFeature.getPlaceId().hashCode() % 300
             if (hueColor < 0) {
                 hueColor += 300
             }
             return@StyleFactory FeatureStyle.Builder()
             // Set the fill color for the state based on the hashed hue color.
               .fillColor(Color.HSVToColor(150, floatArrayOf(hueColor.toFloat(), 1f, 1f)))
               .build()
         }
         return@StyleFactory null
     }
   
     // Apply the style factory function to the feature layer.
     areaLevel1Layer?.setFeatureStyle(styleFactory)
   }