title: onUserLocationChange changes React Native Maps region
body: <p>I'm using MapView from 'react-native-maps'</p>
  
  <p>I can't get the "showsMyLocationButton" to show, so I'm implementing my own.</p>
  
  <p>I want do this without using React Native's geolocation because I find it to be slower than react-native-maps prop showsUserLocation. I use onUserLocationChange event which returns the coordinates. However when firing the onUserLocationChange event and setting a state which contains the userLocation, it automatically updates the region without me explicitly asking for it.</p>
  
  <p>This is my code:</p>
  
  <pre><code>display_my_location(coordinate){
    alert("region changed")
    this.setState({
      region: {
        latitude: coordinate.latitude,
        longitude: coordinate.longitude,
        latitudeDelta: 0.004,
        longitudeDelta: 0.004
      },
    });
  }
  
  setUserLocation(coordinate){
    //alert("User location changed MAP SHOULDNT MOVE")
    this.setState({
      userLocation: {
        latitude: coordinate.latitude,
        longitude: coordinate.longitude,
        latitudeDelta: 0.004,
        longitudeDelta: 0.004
      }
    })
  }
  
  &lt;MapView
        style={styles.map}
        showsMyLocationButton={true}
        onUserLocationChange={locationChangedResult =&gt; this.setUserLocation(locationChangedResult.nativeEvent.coordinate)}
        initialRegion={this.state.region_amon}
        showsUserLocation={true}
        region={this.state.region}
        mapType={this.state.map_style}
        showsCompass = {true}
        showsMyLocationButton={true}
        chacheEnabled={false}
        zoomEnabled={true}
  </code></pre>