Get current location, latitude and longitude in ReactNative using react-native-maps - react-native

Question

I am developing a map location. When I click in some particular place I get the latitude and longitude, but not the current location, latitude and longitude.
I don't know how to find out.
How can I get them and how can I put the marker at that position?
Here is my code:
class Maps extends React.Component {
constructor(props) {
super(props);
this.state = {
region: {
latitude: LATITUDE,
longitude: LONGITUDE,
latitudeDelta: LATITUDE_DELTA,
longitudeDelta: LONGITUDE_DELTA,
},
marker: {
latlng:{
latitude: null,
longitude: null,
latitudeDelta: LATITUDE_DELTA,
longitudeDelta: LONGITUDE_DELTA
}
}
}
}
componentDidMount() {
navigator.geolocation.getCurrentPosition (
(position) => { alert("value:" + position) },
(error) => { console.log(error) },
{
enableHighAccuracy: true,
timeout: 20000,
maximumAge: 10000
}
)
}
onMapPress(e) {
alert("coordinates:" + JSON.stringify(e.nativeEvent.coordinate))
this.setState({
marker: [{ coordinate: e.nativeEvent.coordinate }]
})
}
render() {
return (
<View style={styles.container}>
<View style={{flexGrow:1}}>
<MapView
ref="map"
provider={this.props.provider}
style={styles.map}
onPress={this.onMapPress.bind(this)}
provider = {PROVIDER_DEFAULT}
mapType="standard"
zoomEnabled={true}
pitchEnabled={true}
showsUserLocation={true}
followsUserLocation={true}
showsCompass={true}
showsBuildings={true}
showsTraffic={true}
showsIndoors={true}>
</MapView>
</View>
</View>
)
}
}

Answer 1

I did it following these steps using react-native#0.42.3 and react-native-maps#^0.13.1 and using react-native#0.44.0 and react-native-maps#^0.15.2 at the date:
Set a mapRegion object in the state, the last longitude and the last latitude as null:
state = {
mapRegion: null,
lastLat: null,
lastLong: null,
}
Then within your componentDidMount() function watch for each change in the current position:
componentDidMount() {
this.watchID = navigator.geolocation.watchPosition((position) => {
...
});
}
When there are changes update them in your this.state.mapRegion, passing the actual coords and the delta values (mine can be different to yours, so adapt them):
componentDidMount() {
this.watchID = navigator.geolocation.watchPosition((position) => {
// Create the object to update this.state.mapRegion through the onRegionChange function
let region = {
latitude: position.coords.latitude,
longitude: position.coords.longitude,
latitudeDelta: 0.00922*1.5,
longitudeDelta: 0.00421*1.5
}
this.onRegionChange(region, region.latitude, region.longitude);
}, (error)=>console.log(error));
}
Then you need the onRegionChange() function, that's being used to "set" new values to your elements within the componentDidMount() function:
onRegionChange(region, lastLat, lastLong) {
this.setState({
mapRegion: region,
// If there are no new values set the current ones
lastLat: lastLat || this.state.lastLat,
lastLong: lastLong || this.state.lastLong
});
}
Unmount the geolocation on componentWillUnmount():
componentWillUnmount() {
navigator.geolocation.clearWatch(this.watchID);
}
And render the MapView passing your current mapRegion object, the MapView.Marker inside of it is just to show you the current latitude and longitude when they change:
render() {
return (
<View style={{flex: 1}}>
<MapView
style={styles.map}
region={this.state.mapRegion}
showsUserLocation={true}
followUserLocation={true}
onRegionChange={this.onRegionChange.bind(this)}>
<MapView.Marker
coordinate={{
latitude: (this.state.lastLat + 0.00050) || -36.82339,
longitude: (this.state.lastLong + 0.00050) || -73.03569,
}}>
<View>
<Text style={{color: '#000'}}>
{ this.state.lastLong } / { this.state.lastLat }
</Text>
</View>
</MapView.Marker>
</MapView>
</View>
);
}
Add the StyleSheet.absoluteFillObject for your map in order to render it properly using the whole width and height of your device.
const styles = StyleSheet.create({
map: {
...StyleSheet.absoluteFillObject,
}
});
So for your onPress() function you could do something similar to the onRegionChange(), that's to get the actual coordinates and to set them:
onMapPress(e) {
let region = {
latitude: e.nativeEvent.coordinate.latitude,
longitude: e.nativeEvent.coordinate.longitude,
latitudeDelta: 0.00922*1.5,
longitudeDelta: 0.00421*1.5
}
this.onRegionChange(region, region.latitude, region.longitude);
}
Check the full code on expo.io (although react-native-maps isn't installed)

Answer 2

I suggest you to read this official documentation about geolocalisation: https://facebook.github.io/react-native/docs/geolocation.html
Then, with the current location, you can put that information into your state:
navigator.geolocation.getCurrentPosition((position) => {
this.setState({position: {longitude: position.longitude, latitude: position.latitude}});
}, (error) => {
alert(JSON.stringify(error))
}, {
enableHighAccuracy: true,
timeout: 20000,
maximumAge: 1000
});
You will be able next, in your render method, to compose your final view with a marker:
render() {
return (
<MapView ...>
<MapView.Marker
coordinate={this.state.position}
title="title"
description="description"
/>
</MapView>
)
}

Answer 3

Look for location permission using the following code:
try {
const granted = await PermissionsAndroid.request(
PermissionsAndroid.PERMISSIONS.ACCESS_FINE_LOCATION
)
if (granted === PermissionsAndroid.RESULTS.GRANTED) {
alert("You can use the location")
}
else {
alert("Location permission denied")
}
}
catch (err) {
console.warn(err)
}
Fetch the current location latitude and longitude using the following code:
this.watchID = navigator.geolocation.watchPosition((position) => {
let region = {
latitude: position.coords.latitude,
longitude: position.coords.longitude,
latitudeDelta: 0.00922*1.5,
longitudeDelta: 0.00421*1.5
}
}