App.js

export default class FAB extends Component {
  ...
  ...
​
  render() { 
    const { data } = this.state; 
    return ( 
      <View style={styles.container}>
        ...
        ...
        <TouchableOpacity onPress={() => alert('FAB clicked')} style={styles.fab}>
          <Text style={styles.fabIcon}>+</Text>
        </TouchableOpacity>
      </View>
    )
  }
}
const styles = StyleSheet.create({ 
  ...
  ...
  fab: { 
    position: 'absolute', 
    width: 56, 
    height: 56, 
    alignItems: 'center', 
    justifyContent: 'center', 
    right: 20, 
    bottom: 20, 
    backgroundColor: '#03A9F4', 
    borderRadius: 30, 
    elevation: 8 
    }, 
    fabIcon: { 
      fontSize: 40, 
      color: 'white' 
    }
});