title: React Native Button is still visible but not touchable after setState change
body: <p>I have a render method that checks an array length in my State and displays a button if the length > 0.  Clicking on the button will alter the state array value back to []. </p>
  
  <p>Clicking the button does reset the array value, the state gets change, and the view is re-rendered.  But the button remains visible on the view, but is not touchable, sits behind other elements, and I cannot even inspect in the debug. Its basically just an artifact.</p>
  
  <p>Pretty sure I'm missing a simple react state / render concept. Any thoughts? Thanks.</p>
  
  <p>Here is the render code:</p>
  
  <pre><code>render() {
   return (
    &lt;Container theme={theme} style={{ backgroundColor: '#000000' }}&gt;
      &lt;View style={styles.mapView}&gt;
        &lt;MapView style={styles.map}
          mapType='satellite'
          showsUserLocation={true}
          showsCompass={true}
          followsUserLocation={false}
          onLongPress={(e) =&gt; this.onMapLongPress(e)}
          initialRegion={{
              latitude: 34.186129,
              longitude: -84.546111,
              latitudeDelta: 0.0012,
              longitudeDelta: 0.0012,
          }}&gt;
          {this.state.mapMarkers.map(marker =&gt; (
          &lt;MapView.Marker
            key={marker.key}
            coordinate={marker.coordinate}
            draggable
            centerOffset={{ x: 0, y: -50 }}
            onDragEnd={(e) =&gt; this.onMarkerEndDrag(e, marker.key)}
          &gt;
              &lt;TargetMarker distance={this.calculateTargetDistance(marker.coordinate.latitude, marker.coordinate.longitude)} metric={this.state.distanceUnitMetric.toUpperCase()} /&gt;
          &lt;/MapView.Marker&gt;
        ))}
          { this.state.mapMarkers.length &gt; 0 ? (
              &lt;Button style={styles.deleteTargetButton} onPress={() =&gt; this.setState({mapMarkers: [] })}&gt;
                &lt;Icon name="delete-forever" size={30} color={GOLD_COLOR}/&gt;
              &lt;/Button&gt;
            ) : null
          }
        &lt;/MapView&gt;
      &lt;/View&gt;
    &lt;/Container&gt;
   );
  }
  </code></pre>