<Button style={[styles.margina, styles.button]} onPress={() => this.editReview(f)}>
               <Text>Edit</Text>
                        </Button>

const styles = StyleSheet.create({
    row: {
        flexDirection: 'row',
    },
    space: {
        justifyContent: 'space-between',
    },
    margina: {
        marginVertical: 15,
        marginHorizontal: 10,
    },
    button: {
        width: Dimensions.get('window').width * 0.8,
        height: 10,
        alignSelf: 'center',
    },
});