title: I cant get current location in react native
body: <p>i am using react-native apps to include a map but i can't make it work.
  The map only shows blue map. the marker can be seen but the map is all blue. The map keeps showing the sea only. The GPS is turned on my Android device. Still the map keeps pointing to (longitude, latitude) = (0,0).</p>
  
  <p>How can i solve this? Here's a snippet of my code.</p>
  
  <pre><code>export default class MapsScreen extends Component{
    constructor(props){
      super(props)
  
      this.state = {
        initialPosition:{
          latitude: 0,
          longitude: 0,
          latitudeDelta: 0,
          longitudeDelta: 0,
        },
        markerPosition: {
          latitude: 0,
          longitude: 0,
        }
      }
    }
  
    watchID: ?number = null
  
    componentDidMount() {
  
      navigator.geolocation.getCurrentPosition(
        (position) =&gt; {
  
            var lat = (position.coords.latitude)
            var long = (position.coords.longitude)
            alert(lat + " "+ long )
            var initialRegion ={
              latitude: lat,
              longitude: long,
              latitudeDelta: 0.0922,
              longitudeDelta: 0.05,
            }
  
            this.setState({ initialRegion: initialRegion })
            this.setState({ markerPosition: initialRegion })
        },
  
         (error) =&gt; {alert('Error getting location')
        },
        {
          enableHighAccuracy: true, timeout: 20000, maximumAge: 1000
        }
      )
      this.watchID = navigator.geolocation.watchPosition((position) =&gt; {
        var lat = parseFloat(position.coords.latitude)
        var long = parseFloat(position.coords.longitude)
        var lastRegion = {
          latitude: lat,
          longitude: long,
          longitudeDelta: 0.0922,
          latitudeDelta: 0.05,
        }   
        this.setState({ initialRegion: lastRegion })
        this.setState({ markerPosition: lastRegion })
      })
    }
    componentWillMount() {
      navigator.geolocation.clearWatch(this.watchID)
    }
  render(){
      return(
        &lt;MapView
          initialRegion={this.state.initialPosition}
          style= {{ height: 250, width: '100%'}}
        &gt;
          &lt;MapView.Marker
            coordinate = {this.state.markerPosition}
           &gt;
           &lt;/MapView.Marker&gt;
          &lt;/MapView&gt;
  
      )
    }
  }
  </code></pre>
  
  <p>i'm using
  "react": "16.3.0-alpha.1",
  "react-native": "0.54.0-rc.3",
  "react-native-maps": "^0.20.1",</p>
  
  <p>Please help me
  Thank you</p>