ArcGIS for Android 100.3.0（11）：FeatureLayer(要素图层)

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概述

FeatureLayer(要素图层)

表示由要素组成的图层; FeatureLayer中的要素包括几何和一组一致的字段。FeatureLayer中的功能可以显示在地图上，查询，编辑和选择（以视觉方式突出显示）。

每个FeatureLayer对应一个FeatureTable，它被传递给FeatureLayer构造函数。

FeatureTable

表示要素的表。

FeatureTable提供queryFeaturesAsync(QueryParameters)空间和属性查询，以及添加，更新和删除功能的方法。

使用构造函数创建FeatureTable子类的实例。FeatureTable用于创建FeatureLayer。FeatureLayer添加到地图后，将在地图中显示表格的要素。

要素服务（Feature Service）

String sample_service_url = "http://sampleserver6.arcgisonline.com/arcgis/rest/services/Energy/Geology/FeatureServer/9";

mMapView = (MapView) findViewById(R.id.mapView);

ArcGISMap map = new ArcGISMap(Basemap.createTerrainWithLabels());
map.setInitialViewpoint(new Viewpoint(new Point(-13176752, 4090404, SpatialReferences.getWebMercator()), 500000));

ServiceFeatureTable serviceFeatureTable = new ServiceFeatureTable(sample_service_url);
FeatureLayer featureLayer = new FeatureLayer(serviceFeatureTable);
map.getOperationalLayers().add(featureLayer);
mMapView.setMap(map);

Geodatabase

包含离线要素数据的移动地理数据库。

Geodatabase类用于打开和访问移动地理数据库的内容。地理数据库是ArcGIS服务（由GeodatabaseSyncTask创建）创建的数据的脱机副本，或者可以使用ArcMap或ArcGIS Pro创建。地理数据库包含一个或多个GeodatabaseFeatureTables。每个都GeodatabaseFeatureTable包含属性数据。对于空间要素，它还存储几何和渲染信息。

GeodatabaseFeatureTable可用于创建FeatureLayer可添加到地图并使用mapview查看的地理数据库。

地理数据库实现可加载的接口; 加载地理数据库后，可以访问地理数据库要素表。

 private void loadGeodatabase() {
        String path = Environment.getExternalStorageDirectory().getAbsolutePath() + "LA_Trails.geodatabase";
        final Geodatabase geodatabase = new Geodatabase(path);
        geodatabase.loadAsync();
        geodatabase.addDoneLoadingListener(() -> {
            if (geodatabase.getLoadStatus() == LoadStatus.LOADED) {
                GeodatabaseFeatureTable geodatabaseFeatureTable = geodatabase.getGeodatabaseFeatureTable("Trailheads");
                geodatabaseFeatureTable.loadAsync();
                final FeatureLayer featureLayer = new FeatureLayer(geodatabaseFeatureTable);
                featureLayer.addDoneLoadingListener(() -> {
                    if (featureLayer.getLoadStatus() == LoadStatus.LOADED) {
                        // set viewpoint to the feature layer's extent
                        mMapView.setViewpointAsync(new Viewpoint(featureLayer.getFullExtent()));
                    } else {
                        Toast.makeText(FeatureLayerGeodatabaseActivity.this, "Feature Layer failed to load!", Toast.LENGTH_LONG).show();
                        Log.e(TAG, "Feature Layer failed to load!");
                    }
                });
                // add feature layer to the map
                mMapView.getMap().getOperationalLayers().add(featureLayer);
            } else {
                Toast.makeText(FeatureLayerGeodatabaseActivity.this, "Geodatabase failed to load!", Toast.LENGTH_LONG).show();
                Log.e(TAG, "Geodatabase failed to load!");
            }
        });
    }

GeoPackage

GeoPackage是一种开放的，基于标准的，独立于平台的，可移植的，自我描述的紧凑格式，用于传输地理空间信息。它是一个独立于平台的SQLite数据库文件，包含GeoPackage数据和元数据表。

 /**
     * Opens a GeoPackage from local storage and adds it to a map.
     */
    private void openGeoPackage() {

        // Get the full path to the local GeoPackage
        String geoPackagePath = Environment.getExternalStorageDirectory().getAbsolutePath() + "/AuroraCO.gpkg";

        // Open the GeoPackage
        GeoPackage geoPackage = new GeoPackage(geoPackagePath);
        geoPackage.loadAsync();
        geoPackage.addDoneLoadingListener(() -> {
            if (geoPackage.getLoadStatus() == LoadStatus.LOADED) {
                // Read the feature tables and get the first one
                FeatureTable geoPackageTable = geoPackage.getGeoPackageFeatureTables().get(0);

                // Make sure a feature table was found in the package
                if (geoPackageTable == null) {
                    Toast.makeText(this, "No feature table found in the package!", Toast.LENGTH_LONG).show();
                    Log.e(TAG, "No feature table found in this package!");
                    return;
                }

                // Create a layer to show the feature table
                FeatureLayer featureLayer = new FeatureLayer(geoPackageTable);

                // Add the feature table as a layer to the map (with default symbology)
                mMap.getOperationalLayers().add(featureLayer);
            } else {
                Toast.makeText(this, "GeoPackage failed to load! " + geoPackage.getLoadError(), Toast.LENGTH_LONG).show();
                Log.e(TAG, "GeoPackage failed to load!" + geoPackage.getLoadError());
            }
        });
    }

shp文件

 private void featureLayerShapefile() {
        ShapefileFeatureTable shapefileFeatureTable = new ShapefileFeatureTable(
                Environment.getExternalStorageDirectory().getAbsolutePath() + "/xhj.shp");

        shapefileFeatureTable.loadAsync();
        shapefileFeatureTable.addDoneLoadingListener(() -> {
            if (shapefileFeatureTable.getLoadStatus() == LoadStatus.LOADED) {

                // create a feature layer to display the shapefile
                FeatureLayer shapefileFeatureLayer = new FeatureLayer(shapefileFeatureTable);

                // add the feature layer to the map
                mMapView.getMap().getOperationalLayers().add(shapefileFeatureLayer);

                // zoom the map to the extent of the shapefile
                mMapView.setViewpointAsync(new Viewpoint(shapefileFeatureLayer.getFullExtent()));
            } else {
                String error = "Shapefile feature table failed to load: " + shapefileFeatureTable.getLoadError().toString();
                Toast.makeText(this, error, Toast.LENGTH_LONG).show();
                Log.e(TAG, error);
            }
        });
    }