Multiselect / Single-Select dropdown.

Dropdown.tsx

import { MaterialIcons } from "@expo/vector-icons";
import React, { useCallback, useEffect, useMemo, useState } from "react";
import {
  FlatList,
  Image,
  Pressable,
  StyleSheet,
  Text,
  TouchableOpacity,
  View,
  ViewStyle,
  TextStyle,
  LayoutAnimation,
  Platform,
  UIManager,
  ListRenderItem,
} from "react-native";
import DashedLine from "react-native-dashed-line";
import { RFValue } from "react-native-responsive-fontsize";

// Enable LayoutAnimation for Android
if (Platform.OS === 'android') {
  UIManager.setLayoutAnimationEnabledExperimental?.(true);
}

export interface DropdownItem<T = any> {
  id: string | number;
  label: string;
  value: T;
  selected?: boolean;
  disabled?: boolean;
  icon?: string | { uri: string };
  meta?: Record<string, any>;
}

export interface DropdownStyles {
  container?: ViewStyle;
  button?: ViewStyle;
  buttonText?: TextStyle;
  dropdown?: ViewStyle;
  item?: ViewStyle;
  itemText?: TextStyle;
  selectedItem?: ViewStyle;
  selectedItemText?: TextStyle;
  disabledItem?: ViewStyle;
  disabledItemText?: TextStyle;
  separator?: ViewStyle;
  icon?: ViewStyle;
}

export interface DropdownProps<T = any> {
  items: DropdownItem<T>[];
  value?: T | T[];
  placeholder?: string;
  multiSelect?: boolean;
  searchable?: boolean;
  maxHeight?: number;
  minHeight?: number;
  loading?: boolean;
  disabled?: boolean;
  showIcon?: boolean;
  iconPosition?: 'left' | 'right';
  customIcon?: React.ReactNode;
  styles?: DropdownStyles;
  onChange?: (value: T | T[], items: DropdownItem<T>[]) => void;
  onOpen?: () => void;
  onClose?: () => void;
  renderItem?: ListRenderItem<DropdownItem<T>>;
  keyExtractor?: (item: DropdownItem<T>) => string;
  filterFunction?: (searchText: string, item: DropdownItem<T>) => boolean;
}

function Dropdown<T = any>({
  items,
  value,
  placeholder = "Select",
  multiSelect = false,
  searchable = false,
  maxHeight = 300,
  minHeight = 0,
  loading = false,
  disabled = false,
  showIcon = true,
  iconPosition = 'right',
  customIcon,
  styles: customStyles,
  onChange,
  onOpen,
  onClose,
  renderItem,
  keyExtractor,
  filterFunction,
}: DropdownProps<T>) {
  const [isOpen, setIsOpen] = useState(false);
  const [searchText, setSearchText] = useState("");
  const [selectedItems, setSelectedItems] = useState<DropdownItem<T>[]>([]);

  // Memoized filtered items
  const filteredItems = useMemo(() => {
    if (!searchable || !searchText) return items;
    return items.filter(item => 
      filterFunction 
        ? filterFunction(searchText, item)
        : item.label.toLowerCase().includes(searchText.toLowerCase())
    );
  }, [items, searchText, filterFunction]);

  // Initialize selected items based on value prop
  useEffect(() => {
    const initialSelected = items.filter(item => 
      Array.isArray(value) 
        ? value.includes(item.value)
        : item.value === value
    );
    setSelectedItems(initialSelected);
  }, [value, items]);

  const toggleDropdown = useCallback(() => {
    if (disabled) return;
    
    LayoutAnimation.configureNext(LayoutAnimation.Presets.easeInEaseOut);
    setIsOpen(prev => !prev);
    
    if (!isOpen) {
      onOpen?.();
    } else {
      onClose?.();
    }
  }, [disabled, isOpen, onOpen, onClose]);

  const handleSelect = useCallback((item: DropdownItem<T>) => {
    if (item.disabled) return;

    let newSelected: DropdownItem<T>[];
    if (multiSelect) {
      newSelected = selectedItems.some(i => i.id === item.id)
        ? selectedItems.filter(i => i.id !== item.id)
        : [...selectedItems, item];
    } else {
      newSelected = [item];
      toggleDropdown();
    }

    setSelectedItems(newSelected);
    onChange?.(
      multiSelect 
        ? newSelected.map(i => i.value)
        : newSelected[0]?.value,
      newSelected
    );
  }, [multiSelect, selectedItems, onChange, toggleDropdown]);

  const renderDefaultItem: ListRenderItem<DropdownItem<T>> = ({ item }) => {
    const isSelected = selectedItems.some(i => i.id === item.id);
    const isDisabled = item.disabled;

    return (
      <TouchableOpacity
        style={[
          defaultStyles.item,
          customStyles?.item,
          isSelected && {...defaultStyles.selectedItem, ...customStyles?.selectedItem},
          isDisabled && {...defaultStyles.disabledItem, ...customStyles?.disabledItem}
        ]}
        onPress={() => handleSelect(item)}
        disabled={isDisabled}
      >
        <View style={defaultStyles.itemContent}>
          {item.icon && (
            <Image
              source={typeof item.icon === 'string' ? { uri: item.icon } : item.icon}
              style={[defaultStyles.itemIcon, customStyles?.icon]}
            />
          )}
          <Text 
            style={[
              defaultStyles.itemText,
              customStyles?.itemText,
              isSelected && {...defaultStyles.selectedItemText, ...customStyles?.selectedItemText},
              isDisabled && {...defaultStyles.disabledItemText, ...customStyles?.disabledItemText}
            ]}
            numberOfLines={1}
          >
            {item.label}
          </Text>
          {multiSelect && (
            <MaterialIcons
              name={isSelected ? "check-box" : "check-box-outline-blank"}
              size={24}
              color={isSelected ? "#2196F3" : "#757575"}
            />
          )}
        </View>
      </TouchableOpacity>
    );
  };

  const displayValue = useMemo(() => {
    if (selectedItems.length === 0) return placeholder;
    return selectedItems
      .map(item => item.label)
      .join(", ");
  }, [selectedItems, placeholder]);

  return (
    <View style={[defaultStyles.container, customStyles?.container]}>
      <Pressable
        style={[
          defaultStyles.button,
          customStyles?.button,
          disabled && defaultStyles.buttonDisabled,
          isOpen && defaultStyles.buttonOpen
        ]}
        onPress={toggleDropdown}
        disabled={disabled}
      >
        {iconPosition === 'left' && showIcon && (
          customIcon || (
            <MaterialIcons
              name={isOpen ? "keyboard-arrow-up" : "keyboard-arrow-down"}
              size={24}
              color="#757575"
            />
          )
        )}
        <Text style={[defaultStyles.buttonText, customStyles?.buttonText]}>
          {displayValue}
        </Text>
        {iconPosition === 'right' && showIcon && (
          customIcon || (
            <MaterialIcons
              name={isOpen ? "keyboard-arrow-up" : "keyboard-arrow-down"}
              size={24}
              color="#757575"
            />
          )
        )}
      </Pressable>

      {isOpen && (
        <View 
          style={[
            defaultStyles.dropdown,
            { maxHeight },
            customStyles?.dropdown
          ]}
        >
          {searchable && (
            <TextInput
              style={defaultStyles.searchInput}
              placeholder="Search..."
              value={searchText}
              onChangeText={setSearchText}
              autoCorrect={false}
            />
          )}
          <FlatList
            data={filteredItems}
            renderItem={renderItem || renderDefaultItem}
            keyExtractor={keyExtractor || (item => item.id.toString())}
            ItemSeparatorComponent={() => (
              <DashedLine
                style={[defaultStyles.separator, customStyles?.separator]}
                dashColor="#E0E0E0"
              />
            )}
            style={{ flexGrow: 0 }}
            keyboardShouldPersistTaps="handled"
            ListEmptyComponent={() => (
              <Text style={defaultStyles.emptyText}>
                {loading ? "Loading..." : "No items found"}
              </Text>
            )}
          />
        </View>
      )}
    </View>
  );
}

const defaultStyles = StyleSheet.create({
  container: {
    position: 'relative',
    zIndex: 1000,
  },
  button: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'space-between',
    paddingHorizontal: 16,
    paddingVertical: 12,
    backgroundColor: '#fff',
    borderWidth: 1,
    borderColor: '#E0E0E0',
    borderRadius: 8,
  },
  buttonOpen: {
    borderBottomLeftRadius: 0,
    borderBottomRightRadius: 0,
    borderBottomWidth: 0,
  },
  buttonDisabled: {
    backgroundColor: '#F5F5F5',
    opacity: 0.7,
  },
  buttonText: {
    flex: 1,
    fontSize: RFValue(16),
    color: '#212121',
    marginHorizontal: 8,
  },
  dropdown: {
    position: 'absolute',
    top: '100%',
    left: 0,
    right: 0,
    backgroundColor: '#fff',
    borderWidth: 1,
    borderTopWidth: 0,
    borderColor: '#E0E0E0',
    borderBottomLeftRadius: 8,
    borderBottomRightRadius: 8,
    elevation: 5,
    shadowColor: '#000',
    shadowOffset: { width: 0, height: 2 },
    shadowOpacity: 0.25,
    shadowRadius: 3.84,
  },
  searchInput: {
    margin: 8,
    paddingHorizontal: 12,
    paddingVertical: 8,
    borderWidth: 1,
    borderColor: '#E0E0E0',
    borderRadius: 4,
    fontSize: RFValue(14),
  },
  item: {
    padding: 12,
  },
  itemContent: {
    flexDirection: 'row',
    alignItems: 'center',
  },
  itemIcon: {
    width: 24,
    height: 24,
    marginRight: 8,
  },
  itemText: {
    flex: 1,
    fontSize: RFValue(14),
    color: '#212121',
  },
  selectedItem: {
    backgroundColor: '#E3F2FD',
  },
  selectedItemText: {
    color: '#2196F3',
    fontWeight: '600',
  },
  disabledItem: {
    opacity: 0.5,
  },
  disabledItemText: {
    color: '#9E9E9E',
  },
  separator: {
    marginHorizontal: 8,
  },
  emptyText: {
    padding: 16,
    textAlign: 'center',
    color: '#757575',
  },
});

export default Dropdown;

Updated Box styling.

fixed selectedValue issue.

added more style props

update to handle more types