Data FlatList, renderItem, dan keyExtractor
Kirim array ke prop data milik FlatList, implementasikan renderItem untuk mengembalikan komponen baris bergaya, lalu sediakan keyExtractor agar identitas daftar tetap stabil.
Data FlatList, renderItem, dan keyExtractor adalah pelajaran React Native Academy gratis di CoddyKit. Ini adalah pelajaran 1 dari 4. Kamu bisa membaca pelajaran lengkapnya di bawah secara gratis — lalu praktikkan langsung di browser dengan editor kode bawaan dan tutor AI 24/7. Ini adalah bagian dari jalur belajar React Native Academy, dan progresmu tersinkronisasi di web dan aplikasi CoddyKit. Kursus React Native Academy mencakup 4 pelajaran total.
Bagian dari pelajaran ini belum diterjemahkan dan ditampilkan dalam bahasa Inggris.
Why FlatList Instead of ScrollView?
ScrollView renders all its children at once, which becomes slow when displaying hundreds of items. FlatList virtualizes the list — it only renders the items currently visible on screen plus a small buffer, dramatically reducing memory usage and improving scroll performance for large datasets.
The data Prop
Pass your array of items to the data prop. FlatList iterates over this array and calls renderItem for each element. The array can contain any kind of JavaScript objects. Changes to the data array trigger a re-render of affected list items.
const DATA = [
{ id: '1', name: 'Alice' },
{ id: '2', name: 'Bob' },
{ id: '3', name: 'Carol' },
];
<FlatList data={DATA} ... />The renderItem Prop
The renderItem prop is a function that receives an object with an item property (the current array element) and must return a React element. This is where you define how each row looks. Keep it as a stable reference using useCallback to avoid unnecessary re-renders.
const renderItem = ({ item }) => (
<View style={styles.row}>
<Text>{item.name}</Text>
</View>
);
<FlatList
data={DATA}
renderItem={renderItem}
/>The keyExtractor Prop
keyExtractor tells FlatList how to extract a unique string key from each item. React uses these keys to track which items changed during re-renders. Without a proper key extractor FlatList falls back to the array index, which can cause subtle bugs during data mutations.
<FlatList
data={DATA}
renderItem={renderItem}
keyExtractor={(item) => item.id}
/>A Complete FlatList Example
Combining data, renderItem, and keyExtractor gives you a fully functional, scrollable, virtualized list. You can style the rows inside renderItem just like any other component. FlatList automatically handles scroll and touch events.
import { FlatList, View, Text, StyleSheet } from 'react-native';
const DATA = [
{ id: '1', title: 'First Item' },
{ id: '2', title: 'Second Item' },
{ id: '3', title: 'Third Item' },
];
export default function App() {
return (
<FlatList
data={DATA}
keyExtractor={(item) => item.id}
renderItem={({ item }) => (
<View style={styles.item}>
<Text>{item.title}</Text>
</View>
)}
/>
);
}
const styles = StyleSheet.create({
item: { padding: 16, borderBottomWidth: 1, borderColor: '#eee' },
});Adding a List Header and Footer
Use ListHeaderComponent to render content above the list (such as a search bar or page title) and ListFooterComponent for content below (such as a loading spinner when fetching more data). These components scroll with the list, unlike a view placed outside FlatList.
<FlatList
data={DATA}
renderItem={renderItem}
keyExtractor={(item) => item.id}
ListHeaderComponent={() => <Text style={styles.header}>Users</Text>}
ListFooterComponent={() => <ActivityIndicator />}
/>Empty List with ListEmptyComponent
When the data array is empty, FlatList renders nothing by default. Provide a ListEmptyComponent to display a placeholder message or illustration when there are no items. This is much cleaner than wrapping FlatList in a conditional.
<FlatList
data={filteredData}
renderItem={renderItem}
keyExtractor={(item) => item.id}
ListEmptyComponent={() => (
<Text style={styles.empty}>No results found</Text>
)}
/>Item Separators with ItemSeparatorComponent
Instead of adding border styles directly to item rows, use ItemSeparatorComponent to render a separator between items. React Native only renders the separator between items, not before the first or after the last, which avoids double borders at the edges.
const Separator = () => (
<View style={{ height: 1, backgroundColor: '#eee' }} />
);
<FlatList
data={DATA}
renderItem={renderItem}
keyExtractor={(item) => item.id}
ItemSeparatorComponent={Separator}
/>Horizontal FlatList
Set the horizontal prop to true to render a horizontally scrolling list. This is useful for carousels, category chips, or story rows. The showsHorizontalScrollIndicator prop can hide the scroll bar for a cleaner look.
<FlatList
horizontal
showsHorizontalScrollIndicator={false}
data={categories}
renderItem={({ item }) => (
<View style={styles.chip}>
<Text>{item.label}</Text>
</View>
)}
keyExtractor={(item) => item.id}
/>Scrolling to an Index Programmatically
Use the ref on FlatList and call flatListRef.current.scrollToIndex({ index, animated: true }) to jump to a specific item. You can also use scrollToOffset for pixel-level control or scrollToEnd to scroll to the bottom of the list.
const flatListRef = useRef(null);
const scrollToTop = () => {
flatListRef.current.scrollToIndex({ index: 0, animated: true });
};
<FlatList ref={flatListRef} data={DATA} renderItem={renderItem} />Avoiding Common FlatList Mistakes
Avoid defining renderItem as an anonymous arrow function directly in JSX (renderItem={() => ...}). This creates a new function reference on every render, causing every row to re-render unnecessarily. Define it outside the JSX or memoize it with useCallback. Also never use an array index as the key — always use a stable unique ID.
// Bad: anonymous function in JSX
<FlatList renderItem={({ item }) => <Row item={item} />} />
// Good: stable reference
const renderItem = useCallback(({ item }) => <Row item={item} />, []);
<FlatList renderItem={renderItem} />Quick Check
Test your understanding of FlatList data, renderItem, and keyExtractor from this lesson.
Lesson Recap
In this lesson you learned: FlatList virtualizes large lists by only rendering visible items, renderItem defines the appearance of each row, and keyExtractor provides stable unique keys for efficient React reconciliation. Next up we explore pull-to-refresh and infinite scroll with load more.
Pertanyaan yang Sering Diajukan
Apakah pelajaran “Data FlatList, renderItem, dan keyExtractor” gratis?
Ya — teks lengkap “Data FlatList, renderItem, dan keyExtractor” gratis dibaca di sini di web. Untuk praktiknya secara interaktif (editor kode bawaan dan tutor AI 24/7) dan buka sisa kursus React Native Academy, upgrade ke CoddyKit PRO. Kursus React Native Academy mencakup 4 pelajaran total.
Apa yang akan aku pelajari di “Data FlatList, renderItem, dan keyExtractor”?
Kirim array ke prop data milik FlatList, implementasikan renderItem untuk mengembalikan komponen baris bergaya, lalu sediakan keyExtractor agar identitas daftar tetap stabil. Kamu berlatih React Native Academy dengan kode praktik yang langsung kamu jalankan di browser, dan tutor AI 24/7 menjawab pertanyaanmu saat kamu mengerjakan pelajaran ini.
Apakah aku perlu pengalaman untuk memulai React Native Academy?
Tidak diperlukan pengalaman sebelumnya. React Native Academy di CoddyKit dirancang untuk pemula hingga pelajar tingkat lanjut, jadi kamu bisa memulai di sini atau dari awal dan belajar sesuai kecepatan kamu sendiri. Ini adalah pelajaran 1 dari 4.
Berapa lama pelajaran “Data FlatList, renderItem, dan keyExtractor” memakan waktu?
Sebagian besar pelajaran CoddyKit memakan waktu sekitar 5–10 menit. Setiap pelajaran ringkas dan interaktif, jadi kamu membuat kemajuan stabil dan melanjutkan dari tempat kamu tinggalkan di web dan aplikasi.
Bisakah aku menulis dan menjalankan kode dalam pelajaran React Native Academy ini?
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Semua pelajaran dalam kursus ini
- Data FlatList, renderItem, dan keyExtractor
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