Query Features in box
This example shows how to Query features in the box on MapView
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Query features about existing layer id and filter
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Query features about custom layer id
For all code examples, refer to Android Maps SDK Code Examples
activity_query_feature_and_symbol.xml view source
1<?xml version="1.0" encoding="utf-8"?>
2<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
3 xmlns:app="http://schemas.android.com/apk/res-auto"
4 android:layout_width="match_parent"
5 android:layout_height="match_parent">
6
7 <ai.nextbillion.maps.core.MapView
8 android:id="@+id/mapView"
9 android:layout_width="match_parent"
10 android:layout_height="match_parent"
11 app:nbmap_cameraTargetLat="52.0907"
12 app:nbmap_cameraTargetLng="5.1214"
13 app:nbmap_cameraZoom="16" />
14
15 <FrameLayout
16 android:id="@+id/selection_box"
17 android:layout_width="150dp"
18 android:layout_height="150dp"
19 android:layout_centerInParent="true"
20 android:alpha="0.3"
21 android:background="@color/palette_mint_100" />
22
23</RelativeLayout>QueryFeatureAndSymbolActivity view source
1package ai.nextbillion;
2
3import android.graphics.Bitmap;
4import android.graphics.BitmapFactory;
5import android.graphics.Color;
6import android.graphics.RectF;
7import android.os.Bundle;
8import android.view.View;
9import android.widget.Toast;
10
11import java.io.IOException;
12import java.util.List;
13
14import ai.nextbillion.kits.geojson.Feature;
15import ai.nextbillion.kits.geojson.FeatureCollection;
16import ai.nextbillion.maps.camera.CameraPosition;
17import ai.nextbillion.maps.camera.CameraUpdateFactory;
18import ai.nextbillion.maps.core.MapView;
19import ai.nextbillion.maps.core.NextbillionMap;
20import ai.nextbillion.maps.core.Style;
21import ai.nextbillion.maps.geometry.LatLng;
22import ai.nextbillion.maps.style.expressions.Expression;
23import ai.nextbillion.maps.style.layers.FillLayer;
24import ai.nextbillion.maps.style.layers.Layer;
25import ai.nextbillion.maps.style.layers.SymbolLayer;
26import ai.nextbillion.maps.style.sources.GeoJsonSource;
27import ai.nextbillion.utils.ResourceUtils;
28import androidx.appcompat.app.AppCompatActivity;
29
30import static ai.nextbillion.maps.style.expressions.Expression.get;
31import static ai.nextbillion.maps.style.expressions.Expression.literal;
32import static ai.nextbillion.maps.style.expressions.Expression.lt;
33import static ai.nextbillion.maps.style.expressions.Expression.toNumber;
34import static ai.nextbillion.maps.style.layers.PropertyFactory.fillColor;
35import static ai.nextbillion.maps.style.layers.PropertyFactory.iconImage;
36
37/**
38 * Demo's query rendered features
39 */
40public class QueryFeatureAndSymbolActivity extends AppCompatActivity {
41
42 public MapView mapView;
43 private NextbillionMap nextbillionMap;
44
45 @Override
46 protected void onCreate(Bundle savedInstanceState) {
47 super.onCreate(savedInstanceState);
48 setContentView(R.layout.activity_query_feature_and_symbol);
49
50 final View selectionBox = findViewById(R.id.selection_box);
51
52 // Initialize map as normal
53 mapView = (MapView) findViewById(R.id.mapView);
54 mapView.onCreate(savedInstanceState);
55 mapView.getMapAsync(nextbillionMap -> {
56 QueryFeatureAndSymbolActivity.this.nextbillionMap = nextbillionMap;
57
58 CameraPosition position = new CameraPosition.Builder()
59 .target(new LatLng(14.589503119868022, 120.98188196701062))
60 .zoom(16)
61 .bearing(0)
62 .tilt(30)
63 .build();
64 nextbillionMap.animateCamera(CameraUpdateFactory.newCameraPosition(position));
65
66 // Add layer / source
67 final GeoJsonSource source = new GeoJsonSource("highlighted-shapes-source");
68 final Layer layer = new FillLayer("highlighted-shapes-layer", "highlighted-shapes-source")
69 .withProperties(fillColor(Color.YELLOW));
70
71 selectionBox.setOnClickListener(view -> {
72 // Query
73 int top = selectionBox.getTop() - mapView.getTop();
74 int left = selectionBox.getLeft() - mapView.getLeft();
75 RectF box = new RectF(left, top, left + selectionBox.getWidth(), top + selectionBox.getHeight());
76
77 Expression filter = lt(toNumber(get("height")), literal(10));
78 List<Feature> features = nextbillionMap.queryRenderedFeatures(box, filter, "building");
79 List<Feature> symbols = nextbillionMap.queryRenderedFeatures(box, "symbols-layer");
80
81 // Show count
82 Toast.makeText(
83 QueryFeatureAndSymbolActivity.this,
84 String.format("%s buildings in box\n%s symbols in box", features.size(), symbols.size()),
85 Toast.LENGTH_SHORT).show();
86
87 // Update source data
88 source.setGeoJson(FeatureCollection.fromFeatures(features));
89 });
90
91 nextbillionMap.setStyle(new Style.Builder()
92 .fromUri(StyleConstants.NBMAP_STREETS)
93 .withSource(source)
94 .withLayer(layer)
95 , style -> addSymbolLayer(style));
96
97 });
98 }
99
100 public void addSymbolLayer(Style style) {
101 try {
102 String testPoints = ResourceUtils.readRawResource(mapView.getContext(), R.raw.test_points_utrecht);
103 Bitmap markerImage = BitmapFactory.decodeResource(getResources(), R.drawable.nbmap_marker_icon_default);
104
105 style.addImage("test-icon", markerImage);
106 style.addSource(new GeoJsonSource("symbols-source", testPoints));
107 style.addLayer(new SymbolLayer("symbols-layer", "symbols-source")
108 .withProperties(
109 iconImage("test-icon")
110 ));
111 } catch (IOException exception) {
112 exception.printStackTrace();
113 }
114 }
115
116 public NextbillionMap getNextbillionMap() {
117 return nextbillionMap;
118 }
119
120 @Override
121 protected void onStart() {
122 super.onStart();
123 mapView.onStart();
124 }
125
126 @Override
127 protected void onResume() {
128 super.onResume();
129 mapView.onResume();
130 }
131
132 @Override
133 protected void onPause() {
134 super.onPause();
135 mapView.onPause();
136 }
137
138 @Override
139 protected void onStop() {
140 super.onStop();
141 mapView.onStop();
142 }
143
144 @Override
145 protected void onSaveInstanceState(Bundle outState) {
146 super.onSaveInstanceState(outState);
147 mapView.onSaveInstanceState(outState);
148 }
149
150 @Override
151 protected void onDestroy() {
152 super.onDestroy();
153 mapView.onDestroy();
154 }
155
156 @Override
157 public void onLowMemory() {
158 super.onLowMemory();
159 mapView.onLowMemory();
160 }
161}
162The given code is an Android activity that demonstrates how to initialize a MapView, query features on a map, and display the results.
Initializing the MapView:
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The onCreate method initializes the MapView by setting the content view and obtaining a reference to it using findViewById.
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The onCreate method also calls mapView.onCreate(savedInstanceState) to create the MapView and mapView.getMapAsync(this) to get a reference to the NextbillionMap instance when it is ready.
Querying Features of an Existing Layer:
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The code sets up a map and adds a layer called "highlighted-shapes-layer" with a source named "highlighted-shapes-source".
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The selectionBox view is used to define a rectangular area on the map.
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When the selectionBox is clicked, the queryRenderedFeatures method is called to query the features within the defined area.
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The queried features are filtered based on a condition (in this case, the height is less than 10) using an Expression.
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The queried features are displayed in a toast message.
Querying Features of a Custom Layer:
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The code adds a custom symbol layer to the map, which is based on a GeoJSON source named "symbols-source".
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The addSymbolLayer method reads GeoJSON data from a resource file and adds it as a source and layer to the map style.
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The queryRenderedFeatures method is used to query the features within the defined area for the "symbols-layer" specifically.
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The queried features are displayed in a toast message.
Other Lifecycle Methods: The code also includes various lifecycle methods (onStart, onResume, onPause, onStop, onSaveInstanceState, onDestroy, onLowMemory) that should be implemented when using the MapView to properly manage its lifecycle and handle configuration changes.
Note: The code uses the Nextbillion Maps SDK and NextbillionMap class to handle map-related operations. It also utilizes the Style class to define the map's visual style, GeoJsonSource class to add data sources, and various layer classes to display map features.
