Multiple expressions
A newer version of the Maps SDK is available
This page uses v9.7.1 of the Mapbox Maps SDK. A newer version of the SDK is available. Learn about the latest version, v11.3.0, in the Maps SDK documentation.
Note
This example is a part of the Mapbox Android Demo app. You can find the values for all referenced resources in the res directory. For example, see res/values/activity_strings.xml for R.string.* references used in this example.
activity_dds_multiple_expression_integration
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:mapbox="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.mapbox.mapboxandroiddemo.examples.dds.ExpressionIntegrationActivity"
android:orientation="vertical">
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="@+id/change_units_fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
mapbox:fabSize="normal"
android:layout_gravity="bottom|end"
android:layout_margin="16dp"
mapbox:layout_constraintBottom_toBottomOf="parent"
mapbox:layout_constraintRight_toRightOf="parent"/>
<TextView android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:id="@+id/units"
android:elevation="6sp"
android:textSize="18sp"
android:textColor="#fff"
android:layout_margin="34dp"
mapbox:layout_constraintBottom_toBottomOf="parent"
mapbox:layout_constraintRight_toRightOf="parent"/>
<com.mapbox.mapboxsdk.maps.MapView
android:id="@+id/mapView"
android:layout_width="match_parent"
android:layout_height="match_parent"
mapbox:mapbox_cameraTargetLat="40"
mapbox:mapbox_cameraTargetLng="-100"
mapbox:mapbox_cameraZoom="6"/>
</androidx.constraintlayout.widget.ConstraintLayout>
ExpressionIntegrationActivity.java
package com.mapbox.mapboxandroiddemo.examples.dds;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Color;
import android.os.AsyncTask;
import android.os.Bundle;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
import androidx.appcompat.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;
import com.mapbox.geojson.Feature;
import com.mapbox.geojson.FeatureCollection;
import com.mapbox.mapboxandroiddemo.R;
import com.mapbox.mapboxsdk.Mapbox;
import com.mapbox.mapboxsdk.camera.CameraUpdate;
import com.mapbox.mapboxsdk.camera.CameraUpdateFactory;
import com.mapbox.mapboxsdk.geometry.LatLng;
import com.mapbox.mapboxsdk.geometry.LatLngBounds;
import com.mapbox.mapboxsdk.maps.MapView;
import com.mapbox.mapboxsdk.maps.MapboxMap;
import com.mapbox.mapboxsdk.maps.OnMapReadyCallback;
import com.mapbox.mapboxsdk.maps.Style;
import com.mapbox.mapboxsdk.style.expressions.Expression;
import com.mapbox.mapboxsdk.style.layers.SymbolLayer;
import com.mapbox.mapboxsdk.style.sources.GeoJsonSource;
import java.io.InputStream;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import timber.log.Timber;
import static com.mapbox.mapboxsdk.style.expressions.Expression.all;
import static com.mapbox.mapboxsdk.style.expressions.Expression.concat;
import static com.mapbox.mapboxsdk.style.expressions.Expression.division;
import static com.mapbox.mapboxsdk.style.expressions.Expression.eq;
import static com.mapbox.mapboxsdk.style.expressions.Expression.get;
import static com.mapbox.mapboxsdk.style.expressions.Expression.literal;
import static com.mapbox.mapboxsdk.style.expressions.Expression.product;
import static com.mapbox.mapboxsdk.style.expressions.Expression.round;
import static com.mapbox.mapboxsdk.style.expressions.Expression.subtract;
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.iconAllowOverlap;
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.iconIgnorePlacement;
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.iconImage;
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.textAllowOverlap;
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.textColor;
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.textField;
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.textIgnorePlacement;
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.textOffset;
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.textSize;
public class ExpressionIntegrationActivity
extends AppCompatActivity implements OnMapReadyCallback {
private static final String GEOJSON_SRC_ID = "extremes_source_id";
private static final String MIN_TEMP_LAYER_ID = "min_temp_layer_id";
private static final String MAX_TEMP_LAYER_ID = "max_temp_layer_id";
private static final String RED_PIN_IMAGE_ID = "red_pin_id";
private static final String BLUE_PIN_IMAGE_ID = "blue_pin_id";
private static final String DEGREES_C = "℃"; //"\u2103";
private static final String DEGREES_F = "℉"; //"\u2109";
private final List<State> states = new ArrayList<>();
private MapboxMap mapboxMap;
private MapView mapView;
private Menu menu;
private FloatingActionButton unitsFab;
private TextView unitsText;
private boolean isImperial = true;
/**
* weather_data_per_state_before2006.geojson file (found in assets)
* contains various weather related records per state/territory.
* Once that file is parsed we will keep a list of states (with name and bounds info).
* We need bounds of for data shown on map per state.
* We first find out all latLng points per state to be shown, than we create a LatLngBounds
* using those points.
*/
private class State {
List<LatLng> latLongs;
LatLngBounds bounds;
String name;
State(String name, LatLng latLng) {
this.name = name;
latLongs = new ArrayList<>();
latLongs.add(latLng);
bounds = LatLngBounds.from(latLng.getLatitude(), latLng.getLongitude(),
latLng.getLatitude(), latLng.getLongitude());
}
void add(LatLng latLng) {
latLongs.add(latLng);
bounds = new LatLngBounds.Builder().includes(latLongs).build();
}
}
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Mapbox access token is configured here. This needs to be called either in your application
// object or in the same activity which contains the mapview.
Mapbox.getInstance(this, getString(R.string.access_token));
// This contains the MapView in XML and needs to be called after the access token is configured.
setContentView(R.layout.activity_dds_multiple_expression_integration);
unitsFab = findViewById(R.id.change_units_fab);
mapView = findViewById(R.id.mapView);
unitsText = findViewById(R.id.units);
mapView.onCreate(savedInstanceState);
mapView.getMapAsync(this);
}
@Override
public void onMapReady(@NonNull final MapboxMap mapboxMap) {
this.mapboxMap = mapboxMap;
mapboxMap.setStyle(Style.MAPBOX_STREETS, new Style.OnStyleLoaded() {
@Override
public void onStyleLoaded(@NonNull final Style style) {
setUpMapImagePins(style);
new LoadGeoJson(ExpressionIntegrationActivity.this).execute();
}
});
}
private void addDataToMap(@NonNull FeatureCollection featureCollection) {
// Retrieves GeoJSON from local file and adds it to the map
GeoJsonSource geoJsonSource = new GeoJsonSource(GEOJSON_SRC_ID, featureCollection);
if (mapboxMap != null) {
mapboxMap.getStyle(style -> {
style.addSource(geoJsonSource);
initTemperatureLayers(style);
populateMenu();
// show Connecticut by default
int indexOfState = indexOfState("Connecticut");
selectState(states.get(indexOfState).name, indexOfState, style);
// When user clicks the map, start the snapshotting process with the given parameters
unitsFab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (mapboxMap != null) {
changeTemperatureUnits(!isImperial, style);
}
}
});
});
}
}
private static class LoadGeoJson extends AsyncTask<Void, Void, FeatureCollection> {
private WeakReference<ExpressionIntegrationActivity> weakReference;
LoadGeoJson(ExpressionIntegrationActivity activity) {
this.weakReference = new WeakReference<>(activity);
}
@Override
protected FeatureCollection doInBackground(Void... voids) {
try {
ExpressionIntegrationActivity activity = weakReference.get();
if (activity != null) {
InputStream inputStream = activity.getAssets().open("weather_data_per_state_before2006.geojson");
// Initialize FeatureCollection object for future use with layers
FeatureCollection featureCollection = FeatureCollection.fromJson(convertStreamToString(inputStream));
// Find out the states represented in the FeatureCollection
// and bounds of the extreme conditions
if (featureCollection.features() != null) {
for (Feature feature : featureCollection.features()) {
String stateName = feature.getStringProperty("state");
String lat = feature.getStringProperty("latitude");
String lon = feature.getStringProperty("longitude");
LatLng latLng = new LatLng(
Double.parseDouble(lat),
Double.parseDouble(lon));
State state = null;
for (State curState : activity.states) {
if (curState.name.equals(stateName)) {
state = curState;
break;
}
}
if (state == null) {
activity.states.add(activity.createState(stateName, latLng));
} else {
state.add(latLng);
}
}
}
return featureCollection;
}
} catch (Exception exception) {
Timber.d("Exception Loading GeoJSON: %s", exception.toString());
}
return null;
}
static String convertStreamToString(InputStream is) {
Scanner scanner = new Scanner(is).useDelimiter("\\A");
return scanner.hasNext() ? scanner.next() : "";
}
@Override
protected void onPostExecute(@Nullable FeatureCollection featureCollection) {
super.onPostExecute(featureCollection);
ExpressionIntegrationActivity activity = weakReference.get();
if (activity != null && featureCollection != null) {
activity.addDataToMap(featureCollection);
}
}
}
private State createState(String stateName, LatLng latLng) {
return new State(stateName, latLng);
}
/**
* Adds the marker image to the map for use as a SymbolLayer icon
*/
private void setUpMapImagePins(@NonNull Style loadedMapStyle) {
Bitmap icon = BitmapFactory.decodeResource(
this.getResources(), R.drawable.red_marker);
loadedMapStyle.addImage(RED_PIN_IMAGE_ID, icon);
icon = BitmapFactory.decodeResource(
this.getResources(), R.drawable.blue_marker);
loadedMapStyle.addImage(BLUE_PIN_IMAGE_ID, icon);
}
private void initTemperatureLayers(@NonNull Style loadedMapStyle) {
if (mapboxMap != null) {
// Adds a SymbolLayer to display maximum temperature in state
SymbolLayer maxTempLayer = new SymbolLayer(MAX_TEMP_LAYER_ID, GEOJSON_SRC_ID);
maxTempLayer.withProperties(
iconImage(RED_PIN_IMAGE_ID),
textField(getTemperatureValue()),
textSize(17f),
textOffset(new Float[] {0f, -1.75f}),
textColor(Color.RED),
textAllowOverlap(true),
textIgnorePlacement(true),
iconAllowOverlap(true),
iconIgnorePlacement(true)
);
// Only display Maximum Temperature in this layer
maxTempLayer.setFilter(eq(get("element"), literal("All-Time Maximum Temperature")));
loadedMapStyle.addLayer(maxTempLayer);
// Adds a SymbolLayer to display minimum temperature in state
SymbolLayer minTempLayer = new SymbolLayer(MIN_TEMP_LAYER_ID, GEOJSON_SRC_ID);
minTempLayer.withProperties(
iconImage(BLUE_PIN_IMAGE_ID),
textField(getTemperatureValue()),
textSize(17f),
textOffset(new Float[] {0f, -2.5f}),
textColor(Color.BLUE),
textAllowOverlap(true),
textIgnorePlacement(true),
iconAllowOverlap(true),
iconIgnorePlacement(true));
// Only display Minimum Temperature in this layer
minTempLayer.setFilter(eq(get("element"), literal("All-Time Minimum Temperature")));
loadedMapStyle.addLayer(minTempLayer);
unitsText.setText(isImperial ? DEGREES_C : DEGREES_F);
}
}
private void changeTemperatureUnits(boolean isImperial, @NonNull Style loadedMapStyle) {
if (mapboxMap != null && this.isImperial != isImperial) {
this.isImperial = isImperial;
// Apply new units to the data displayed in text fields of SymbolLayers
SymbolLayer maxTempLayer = (SymbolLayer) loadedMapStyle.getLayer(MAX_TEMP_LAYER_ID);
if (maxTempLayer != null) {
maxTempLayer.withProperties(textField(getTemperatureValue()));
}
SymbolLayer minTempLayer = (SymbolLayer) loadedMapStyle.getLayer(MIN_TEMP_LAYER_ID);
if (minTempLayer != null) {
minTempLayer.withProperties(textField(getTemperatureValue()));
}
unitsText.setText(isImperial ? DEGREES_C : DEGREES_F);
}
}
private Expression getTemperatureValue() {
if (isImperial) {
return concat(get("value"), literal(DEGREES_F)); // For imperial we just need to add "F"
}
Expression value = Expression.toNumber(get("value")); // value --> Number
value = subtract(value, Expression.toNumber(literal(32.0))); // value - 32
value = product(value, Expression.toNumber(literal(5.0))); // value * 5
value = division(value, Expression.toNumber(literal(9.0))); // value / 9
value = round(value); // round to nearest int
return concat(Expression.toString(value), literal(DEGREES_C)); // add C at the end
}
@Override
protected void onStart() {
super.onStart();
mapView.onStart();
}
@Override
protected void onResume() {
super.onResume();
mapView.onResume();
}
@Override
protected void onPause() {
mapView.onPause();
super.onPause();
}
@Override
protected void onStop() {
mapView.onStop();
super.onStop();
}
@Override
protected void onDestroy() {
unitsFab.setOnClickListener(null);
if (menu != null) {
menu.clear();
}
states.clear();
mapView.onDestroy();
mapView = null;
mapboxMap = null;
unitsFab = null;
menu = null;
super.onDestroy();
}
@Override
public void onLowMemory() {
super.onLowMemory();
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
mapView.onSaveInstanceState(outState);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
this.menu = menu;
populateMenu();
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (mapboxMap != null) {
Style style = mapboxMap.getStyle();
if (style != null) {
selectState(item.getTitle(), item.getItemId(), style);
}
}
return super.onOptionsItemSelected(item);
}
private void populateMenu() {
if (menu != null) {
for (int id = 0; id < states.size(); id++) {
menu.add(Menu.NONE, id, Menu.NONE, states.get(id).name);
}
}
}
private void selectState(CharSequence stateName, int stateIndex, @NonNull Style loadedMapStyle) {
if (indexOfState(stateName) == stateIndex) {
// Adds a SymbolLayer to display maximum temperature in state
SymbolLayer maxTempLayer = (SymbolLayer) loadedMapStyle.getLayer(MAX_TEMP_LAYER_ID);
// Only display Maximum Temperature in this layer for SELECTED State
if (maxTempLayer != null) {
maxTempLayer.setFilter(all(
eq(get("element"), literal("All-Time Maximum Temperature")),
eq(get("state"), literal(stateName))));
}
// Adds a SymbolLayer to display minimum temperature in state
SymbolLayer minTempLayer = (SymbolLayer) loadedMapStyle.getLayer(MIN_TEMP_LAYER_ID);
// Only display Maximum Temperature in this layer for SELECTED State
if (minTempLayer != null) {
minTempLayer.setFilter(all(
eq(get("element"), literal("All-Time Minimum Temperature")),
eq(get("state"), literal(stateName))));
}
CameraUpdate cameraUpdate =
CameraUpdateFactory.newLatLngBounds(states.get(stateIndex).bounds, 100);
mapboxMap.animateCamera(cameraUpdate);
Toast.makeText(this,
String.format(getString(R.string.temp_change_feedback), stateName),
Toast.LENGTH_LONG).show();
}
}
private int indexOfState(CharSequence name) {
if (name != null) {
for (int i = 0; i < states.size(); i++) {
if (name.equals(states.get(i).name)) {
return i;
}
}
}
return -1;
}
}