mh-rn-component/module/Picker/Columns.js

import React, { useRef, useEffect, useState } from 'react';
import { View, Text, FlatList } from "react-native";
import { randomBaseId } from "../helpers";

const Columns = _ref => {
  let {
    data,
    columnHeight,
    defaultIndex = 0,
    visibleItemCount,
    columnIndex,
    onChange,
    customFieldName,
    ...rest
  } = _ref;
  const customFieldNameValue = customFieldName.value || "value";
  const columnRef = useRef(null);
  const [curIndex, setCurIndex] = useState(defaultIndex);

  const renderColumnItems = (item, index) => {
    const type = typeof item;
    return /*#__PURE__*/React.createElement(View, {
      style: {
        height: columnHeight,
        justifyContent: "center"
      }
    }, /*#__PURE__*/React.createElement(Text, {
      style: {
        color: index === curIndex ? "#333" : "#ccc",
        textAlign: "center"
      }
    }, type === 'number' || type === 'string' ? item : item[customFieldNameValue]));
  };

  const renderColumns = _ref2 => {
    let {
      item,
      index
    } = _ref2;
    return /*#__PURE__*/React.createElement(View, {
      style: {
        flex: 1
      }
    }, renderColumnItems(item, index));
  }; // 占位


  const vacancy = () => {
    const multiple = (visibleItemCount - 1) / 2;
    return /*#__PURE__*/React.createElement(View, {
      style: {
        height: columnHeight * multiple
      }
    });
  };

  const move = index => {
    var _columnRef$current;

    (_columnRef$current = columnRef.current) === null || _columnRef$current === void 0 ? void 0 : _columnRef$current.scrollToIndex({
      viewPosition: 0,
      index: Number(index)
    });
  };

  useEffect(() => {
    rest.cascadeLevel && setCurIndex(0);
  }, [data]);
  useEffect(() => {
    move(curIndex); //!传数组对象和传数组的区别

    onChange(data[curIndex][customFieldNameValue] || data[curIndex], curIndex, columnIndex);
  }, [curIndex]);

  const onScrollEnd = _ref3 => {
    let {
      nativeEvent
    } = _ref3;

    let _index = Number((Number(nativeEvent.contentOffset.y) / columnHeight).toFixed(0));

    if (data.length < _index) {
      _index = data.length - 1;
    } else if (_index < 0) {
      _index = 0;
    }

    if (data.length > _index && _index >= 0) {
      // 节流 只有变化的时候才会调用
      if (Math.abs(_index) !== curIndex) {
        setCurIndex(Math.abs(_index));
      }
    }
  }; // 自定义key值


  const _baseId = randomBaseId();

  const customKey = (item, index) => {
    return `${_baseId}${index}`;
  };

  return /*#__PURE__*/React.createElement(FlatList, {
    showsHorizontalScrollIndicator: false,
    showsVerticalScrollIndicator: false,
    ref: columnRef,
    data: data,
    renderItem: renderColumns,
    ListHeaderComponent: vacancy,
    ListFooterComponent: vacancy,
    keyExtractor: customKey,
    getItemLayout: (data, index) => ({
      length: columnHeight,
      offset: columnHeight * index,
      index
    }),
    onScrollEndDrag: onScrollEnd
  });
};

export default Columns;
//# sourceMappingURL=Columns.js.map