React Native 中的方法是如何工作的？

import React, { Component } from 'react';
import { Alert, AppRegistry, FlatList, Text, TextInput, View } from 'react-native';

export default class PizzaTranslator extends Component {
  constructor(props) {
    super(props);
    this.state = {text: ''};
  }
  _onload() {
    this.abc.scrollTo({x: 0, y: 0, animated: true});
  }

  render() {
    return (
      <View>
        <FlatList
          data={[
            {key: 'Devin'},
            {key: 'Jackson'},
            {key: 'James'},
            {key: 'Joel'},
            {key: 'John'},
            {key: 'Jillian'},
            {key: 'Jimmy'},
            {key: 'Julie'},
            {key: 'Devin'},
            {key: 'Jackson'},
            {key: 'James'},
            {key: 'Joel'},
            {key: 'John'},
          ]}
          renderItem={({item}) => <Text>{item.key}</Text>}
          onScrollBeginDrag={this._onload}
          ref={(FlatList) => {this.abc = FlatList;}}
        />
      </View>
    );
  }
}

// skip this line if using Create React Native App
AppRegistry.registerComponent('AwesomeProject', () => PizzaTranslator);