React Native 之 AppState(应用状态)(二十二)
AppState 是 React Native 提供的一个 API,用于监听应用在前台、后台或未激活状态之间的切换。这对于管理应用的资源、调解应用的界面显示或响应系统变乱(如来电)等场景非常有用。AppState 模块通过监听系统广播的意图(Intents)或应用生命周期变乱来实现其功能。当应用的状态发生变革时(比方,用户切换到另一个应用或返回到主屏幕),系统会发送一个相应的意图或变乱。AppState 模块捕获这些变乱,并通过其提供的 API 将状态变革关照给应用。
import React, { useEffect } from 'react';
import { AppState, Text, View, StyleSheet } from 'react-native';
const AppStateExample = () => {
const handleAppStateChange = (nextAppState) => {
if (nextAppState === 'active') {
console.log('App has come to the foreground!');
} else if (nextAppState === 'background') {
console.log('App has gone to the background!');
} else if (nextAppState === 'inactive') {
console.log('App is in an inactive state!');
}
};
useEffect(() => {
const subscription = AppState.addEventListener('change', handleAppStateChange);
// 清理函数,确保在组件卸载时移除监听器
return () => {
subscription.remove();
};
}, []); // 空依赖数组确保 effect 只在组件挂载和卸载时运行
return (
<View style={styles.container}>
<Text>Open the app switcher (double tap home button) and check the console to see the logs.</Text>
</View>
);
};
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
},
});
export default AppStateExample;
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