import SmartPicker from 'react-native-smart-picker'

...

 this.state = {
            selected: "A",
           
        };

 handleChange(value: string) {
        this.setState({
            selected: value
        });
    }

<ScrollView style={"Your custom styles here"}>
  <View style={{flex: 1, marginTop: 20}}>
    <ScrollView style={styles.container}>
      <SmartPicker
        selectedValue={this.state.selected}
        label='Set you favorite country'
        onValueChange={this.handleChange.bind(this)}
      >
        <Picker.Item label='Austria' value='A' />
        <Picker.Item label='Czechia' value='CZ' />
        <Picker.Item label='Germany' value='DE' />
        <Picker.Item label='Poland' value='PL' />
        <Picker.Item label='Slovakia' value='SLO' />
      </SmartPicker>
    </ScrollView>
  </View>
</ScrollView>