安卓智能地图开发与实施十八：空间要素绘制

日常应用中无论是草图绘制，还是外业采集都需要在移动端进行空间要素的绘制。而ArcGIS Runtime SDK for Android中提供了Geometry、Feature、Graphic，这三者到底如何使用，本文稍微做做解答。

空间要素（Geometry）

Geometries用以在特定地理位置上通过形状来表达真实世界的对象。图层范围、视图范围、GPS定位都是通过Geometries表达实现进一步的数据编辑、空间分析、地理处理、位置与面积量算都离不开空间要素。

Features 与 Graphics

Feature（com.esri.arcgisruntime.data.Feature），存储于Feature Table中，在 Feature Layer中进行显示。包含的Geometry 必须同一类型。包含的属性信息其字段信息必须相同。用以Feature Table中进行更新、删除等操作。
Graphic（com.esri.arcgisruntime.mapping.view. Graphic ），存储于运行内存中，在Graphics OverLay中进行显示。包含的Geometry类型可以不统一。通过类对象直接创建，仅用以绘制性显示。

创建 – 矩形、点

Envelope envelope = 
new Envelope(-123.0, 33.5, -101.0, 48.0, SpatialReferences.getWgs84());
Point pt = 
new Point(34.056295, -117.195800, SpatialReferences.getWgs84());
PointCollection stateCapitalsPST =
 new PointCollection(SpatialReferences.getWgs84());
stateCapitalsPST.add(-121.491014, 38.579065); // Sacramento, CA
stateCapitalsPST.add(-122.891366, 47.039231); // Olympia, WA
stateCapitalsPST.add(-123.043814, 44.93326); // Salem, OR
stateCapitalsPST.add(-119.766999, 39.164885); // Carson City, NV
Multipoint multipoint = new Multipoint(stateCapitalsPST);
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创建 – 线、面

PointCollection borderCAtoNV = 
new PointCollection(SpatialReferences.getWgs84());
borderCAtoNV.add(-119.992, 41.989);
borderCAtoNV.add(-119.994, 38.994);
borderCAtoNV.add(-114.620, 35.0);
Polyline polyline = new Polyline(borderCAtoNV);
PointCollection coloradoCorners =
 new PointCollection(SpatialReferences.getWgs84());
    coloradoCorners.add(-109.048, 40.998);
    coloradoCorners.add(-102.047, 40.998);
    coloradoCorners.add(-102.037, 36.989);
    coloradoCorners.add(-109.048, 36.998);
    Polygon polygon = new Polygon(coloradoCorners);
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空间要素绘制 – SketchEditor

绘制类型（SketchCreationMode）

• POINT
• MULTIPOINT
• POLYLINE
• POLYGON
• FREEHAND_LINE
• FREEHAND_POLYGON

初始化地图

mainMapView = (MapView) findViewById(R.id.mainMapView);
mainBasemap = new Basemap(
        TianDiTuMethodsClass.CreateTianDiTuTiledLayer(
                TianDiTuMethodsClass.LayerType.TIANDITU_VECTOR_2000));
mainBasemap.getBaseLayers().add(
        TianDiTuMethodsClass.CreateTianDiTuTiledLayer(
                TianDiTuMethodsClass.LayerType.TIANDITU_VECTOR_ANNOTATION_CHINESE_2000));
mainArcGISMap = new ArcGISMap(mainBasemap);
mainMapView.setMap(mainArcGISMap);
mainSketchEditor = new SketchEditor();
mainSketchStyle = new SketchStyle();
mainSketchEditor.setSketchStyle(mainSketchStyle);
mainMapView.setSketchEditor(mainSketchEditor);
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启动绘制

mPointButton = (ImageButton) findViewById(R.id.pointSketchButton);
mPointButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        try {
            //mainSketchEditor.stop();
            mainSketchEditor.start(SketchCreationMode.POINT);
        }
        catch (Exception e)
        {
            e.getCause();
        }
    }
});
mPolylineButton = (ImageButton) findViewById(R.id.polylineSketchButton);
mPolylineButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        try {
            //mainSketchEditor.stop();
            mainSketchEditor.start(SketchCreationMode.POLYLINE);
        }
        catch (Exception e)
        {
            e.getCause();
        }
    }
});
mPolygonButton = (ImageButton) findViewById(R.id.polygonSketchButton);
mPolygonButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        try {
            //mainSketchEditor.stop();
            mainSketchEditor.start(SketchCreationMode.POLYGON);
        }
        catch (Exception e)
        {
            e.getCause();
        }
    }
});
mPolylineFreeheadButton = (ImageButton) findViewById(R.id.polylineFreeheadSketchButton);
mPolylineFreeheadButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        try {
            //mainSketchEditor.stop();
            mainSketchEditor.start(SketchCreationMode.FREEHAND_LINE);
        }
        catch (Exception e)
        {
            e.getCause();
        }
    }
});
mPolygonFreeheadButton = (ImageButton) findViewById(R.id.polygonFreeheadSketchButton);
mPolygonFreeheadButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        try {
            //mainSketchEditor.stop();
            mainSketchEditor.start(SketchCreationMode.FREEHAND_POLYGON);
        }
        catch (Exception e)
        {
            e.getCause();
        }
    }
});
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