下拉刷新与加载更多
使用 RefreshControl 实现 onRefresh，让用户下拉重新加载数据，并使用 onEndReached 获取下一页结果。
下拉刷新与加载更多 是 CoddyKit 上的免费 React Native Academy 课时。 这是第 2 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 React Native Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 React Native Academy 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
Why Pull-to-Refresh?
Pull-to-refresh is a mobile-native gesture where the user pulls the list downward to trigger a data reload. It signals to the app that new content should be fetched from the server. React Native's FlatList has built-in support for this gesture through the onRefresh and refreshing props.
The refreshing and onRefresh Props
FlatList's pull-to-refresh requires two props: refreshing (a boolean that shows or hides the spinner) and onRefresh (a callback that runs your data-fetch logic). Set refreshing to true when the fetch starts and back to false when it completes.
const [refreshing, setRefreshing] = useState(false);
const onRefresh = async () => {
setRefreshing(true);
await fetchData();
setRefreshing(false);
};
<FlatList
data={items}
renderItem={renderItem}
keyExtractor={(item) => item.id}
refreshing={refreshing}
onRefresh={onRefresh}
/>Using RefreshControl for Custom Styling
For more control over the spinner's appearance, use the refreshControl prop with a RefreshControl component. This lets you set the spinner's tintColor (iOS) and colors (Android), and even add a custom progressViewOffset for apps with fixed headers.
import { RefreshControl } from 'react-native';
<FlatList
data={items}
renderItem={renderItem}
keyExtractor={(item) => item.id}
refreshControl={
<RefreshControl
refreshing={refreshing}
onRefresh={onRefresh}
tintColor='#6200ee'
colors={['#6200ee', '#03dac5']}
/>
}
/>Infinite Scroll with onEndReached
Infinite scroll (load more / pagination) fetches additional data when the user approaches the bottom of the list. FlatList fires the onEndReached callback when the user scrolls within onEndReachedThreshold of the end. A threshold of 0.5 triggers the callback when the user is halfway to the end.
const [page, setPage] = useState(1);
const [items, setItems] = useState([]);
const loadMore = async () => {
const newItems = await fetchPage(page + 1);
setItems(prev => [...prev, ...newItems]);
setPage(prev => prev + 1);
};
<FlatList
data={items}
renderItem={renderItem}
keyExtractor={(item) => item.id}
onEndReached={loadMore}
onEndReachedThreshold={0.5}
/>Preventing Duplicate Load Calls
onEndReached can fire multiple times in quick succession as the user scrolls. Guard against duplicate fetches with a loading flag. Check the flag at the start of your load function and return early if a fetch is already in progress. Reset the flag once the data is loaded.
const [loadingMore, setLoadingMore] = useState(false);
const loadMore = async () => {
if (loadingMore) return; // guard against duplicates
setLoadingMore(true);
const newItems = await fetchPage(page + 1);
setItems(prev => [...prev, ...newItems]);
setPage(prev => prev + 1);
setLoadingMore(false);
};Footer Spinner for Load More
Show an ActivityIndicator in the ListFooterComponent while the next page is loading. Hide it when all pages are loaded. This gives users a visual cue that more content is coming and prevents them from repeatedly scrolling to try to load more when it is already loading.
const renderFooter = () => {
if (!loadingMore) return null;
return <ActivityIndicator style={{ padding: 16 }} />;
};
<FlatList
data={items}
renderItem={renderItem}
keyExtractor={(item) => item.id}
onEndReached={loadMore}
onEndReachedThreshold={0.5}
ListFooterComponent={renderFooter}
/>Detecting End of Data
Keep a hasMore boolean in state. When your API returns fewer items than the page size, you know there are no more pages. Set hasMore to false and guard the loadMore function with this check. Also update the footer to show an 'End of list' message instead of a spinner.
const [hasMore, setHasMore] = useState(true);
const loadMore = async () => {
if (loadingMore || !hasMore) return;
setLoadingMore(true);
const newItems = await fetchPage(page + 1);
if (newItems.length < PAGE_SIZE) setHasMore(false);
setItems(prev => [...prev, ...newItems]);
setPage(prev => prev + 1);
setLoadingMore(false);
};Combining Refresh and Load More
Pull-to-refresh and load more can coexist in the same FlatList. On refresh, reset the page to 1, clear the existing items, fetch the first page, and reset hasMore to true. The two flows are independent and use separate loading states so they do not interfere with each other.
const onRefresh = async () => {
setRefreshing(true);
setPage(1);
setHasMore(true);
const freshData = await fetchPage(1);
setItems(freshData);
setRefreshing(false);
};onEndReachedThreshold Best Practices
The onEndReachedThreshold value is a fraction of the visible list height, not a pixel value. Setting it to 0.2 triggers loading when 20% of the list content remains visible below the screen. A higher value starts loading earlier for slower APIs; a lower value is better for fast API responses.
// Trigger load more when 20% of list remains
<FlatList
onEndReached={loadMore}
onEndReachedThreshold={0.2}
/>Scroll Position After Refresh
After a refresh replaces the data array, FlatList may retain the old scroll position, making the new content invisible. Call flatListRef.current.scrollToOffset({ offset: 0, animated: true }) after setting fresh data to bring the list back to the top for a polished user experience.
const flatListRef = useRef(null);
const onRefresh = async () => {
setRefreshing(true);
const freshData = await fetchPage(1);
setItems(freshData);
flatListRef.current?.scrollToOffset({ offset: 0, animated: true });
setRefreshing(false);
};Testing Pull-to-Refresh on Emulator
On iOS Simulator, pull-to-refresh works with a trackpad two-finger swipe down on the list. On Android Emulator, click and drag down from a list item. On a physical device, the gesture is natural. Always test both platforms because iOS uses a native spinner while Android uses its own Material-style indicator.
Quick Check
Test your understanding of pull-to-refresh and infinite scroll from this lesson.
Lesson Recap
In this lesson you learned: use the refreshing and onRefresh props to implement pull-to-refresh, use onEndReached with onEndReachedThreshold for infinite scroll, and guard loadMore with a loading flag to prevent duplicate API calls. Next up we explore SectionList for grouped data with headers.
常见问题解答
「下拉刷新与加载更多」课时是免费的吗？
是的 — 「下拉刷新与加载更多」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 React Native Academy 课程的其余内容，请升级到 CoddyKit PRO。 React Native Academy 课程共包含 4 节课。
「下拉刷新与加载更多」这节课中我会学到什么？
使用 RefreshControl 实现 onRefresh，让用户下拉重新加载数据，并使用 onEndReached 获取下一页结果。 你通过在浏览器中直接运行的动手代码来练习 React Native Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 React Native Academy 需要有经验吗？
无需任何先前经验。CoddyKit 上的 React Native Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 2 节课，共 4 节。
「下拉刷新与加载更多」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 React Native Academy 课中编写并运行代码吗？
能。每节 React Native Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。