我按照React native - "this.setState is not a function" trying to animate background color?的建议合并了useEffect()钩子(Hook)后,才遇到此问题
随着以下,我得到
export default props => {
let [fontsLoaded] = useFonts({
'Inter-SemiBoldItalic': 'https://rsms.me/inter/font-files/Inter-SemiBoldItalic.otf?v=3.12',
'SequelSans-RomanDisp' : require('./assets/fonts/SequelSans-RomanDisp.ttf'),
'SequelSans-BoldDisp' : require('./assets/fonts/SequelSans-BoldDisp.ttf'),
'SequelSans-BlackDisp' : require('./assets/fonts/SequelSans-BlackDisp.ttf'),
});
if (!fontsLoaded) {
return <AppLoading />;
} else {
//Set states
const [backgroundColor, setBackgroundColor] = useState(new Animated.Value(0));
useEffect(() => {
setBackgroundColor(new Animated.Value(0));
}, []); // this will be only called on initial mounting of component,
// so you can change this as your requirement maybe move this in a function which will be called,
// you can't directly call setState/useState in render otherwise it will go in a infinite loop.
useEffect(() => {
Animated.timing(this.state.backgroundColor, {
toValue: 100,
duration: 5000
}).start();
}, [backgroundColor]);
var color = this.state.colorValue.interpolate({
inputRange: [0, 300],
outputRange: ['rgba(255, 0, 0, 1)', 'rgba(0, 255, 0, 1)']
});
const styles = StyleSheet.create({
container: { flex: 1,
alignItems: 'center',
justifyContent: 'center',
backgroundColor: color
},
textWrapper: {
height: hp('70%'), // 70% of height device screen
width: wp('80%'), // 80% of width device screen
backgroundColor: '#fff',
justifyContent: 'center',
alignItems: 'center',
},
myText: {
fontSize: hp('2%'), // End result looks like the provided UI mockup
fontFamily: 'SequelSans-BoldDisp'
}
});
return (
<Animated.View style={styles.container}>
<View style={styles.textWrapper}>
<Text style={styles.myText}>Login</Text>
</View>
</Animated.View>
);
}
};
我只是想制作动画以淡化 View 的背景色。我尝试删除第一个useEffect,以防造成一些冗余,但这没有任何作用。我是ReactNative的新手-这是怎么了?编辑:
export default props => {
let [fontsLoaded] = useFonts({
'Inter-SemiBoldItalic': 'https://rsms.me/inter/font-files/Inter-SemiBoldItalic.otf?v=3.12',
'SequelSans-RomanDisp' : require('./assets/fonts/SequelSans-RomanDisp.ttf'),
'SequelSans-BoldDisp' : require('./assets/fonts/SequelSans-BoldDisp.ttf'),
'SequelSans-BlackDisp' : require('./assets/fonts/SequelSans-BlackDisp.ttf'),
});
//Set states
const [backgroundColor, setBackgroundColor] = useState(new Animated.Value(0));
useEffect(() => {
setBackgroundColor(new Animated.Value(0));
}, []); // this will be only called on initial mounting of component,
// so you can change this as your requirement maybe move this in a function which will be called,
// you can't directly call setState/useState in render otherwise it will go in a infinite loop.
useEffect(() => {
Animated.timing(useState(backgroundColor), {
toValue: 100,
duration: 7000
}).start();
}, [backgroundColor]);
// var color = this.state.colorValue.interpolate({
// inputRange: [0, 300],
// outputRange: ['rgba(255, 0, 0, 1)', 'rgba(0, 255, 0, 1)']
// });
//------------------------------------------------------------------->
if (!fontsLoaded) {
return <AppLoading />;
} else {
const styles = StyleSheet.create({
container: { flex: 1,
alignItems: 'center',
justifyContent: 'center',
backgroundColor: backgroundColor
新错误:最佳答案
从useFonts
开始,在您返回<AppLoading />
时,在您的第一个渲染中(仅在猜测中)只有!fontsLoaded
钩子(Hook)会被调用。其余的钩子(Hook)位于else
块中,这意味着在每个渲染器上钩子(Hook)的数量都不相同。
查看https://reactjs.org/docs/hooks-rules.html了解更多说明,尤其是https://reactjs.org/docs/hooks-rules.html#only-call-hooks-at-the-top-level