[英]How do I use setNativeProps in Functional Components? React-native
[英]How to use the useRef hook for setNativeProps in React Native?
我正在嘗試將 React Native 的類組件轉換為涉及useRef
的功能組件。 以下是類組件:
import React, { Component } from "react";
import { AppRegistry, StyleSheet, Text, View, Animated, TouchableWithoutFeedback } from "react-native";
import { interpolateNumber, interpolateRgb } from "d3-interpolate";
export default class animations extends Component {
state = {
animation: new Animated.Value(0)
};
componentWillMount() {
const positionInterpolate = interpolateNumber(0, 200);
const colorInterpolate = interpolateRgb("rgb(255,99,71)", "rgb(99,71,255)");;
this.state.animation.addListener(({value}) => {
const position = positionInterpolate(value);
const color = colorInterpolate(value);
const style = [
styles.box,
{
backgroundColor: color,
transform: [
{translateY: position}
]
}
];
this._view.setNativeProps({ style });
});
}
handlePress = () => {
Animated.timing(this.state.animation, {
toValue: 1,
duration: 500,
}).start();
}
render() {
return (
<View style={styles.container}>
<TouchableWithoutFeedback onPress={this.handlePress}>
<View style={styles.box} ref={view => this._view = view} />
</TouchableWithoutFeedback>
</View>
);
}
}
當我轉換為以下功能組件時,出現以下錯誤:
類型錯誤 someRef.setNativeProps 不是函數。 (在 'someRef.setNativeProps({ style: style })' 中,'someRef.setNativeProps' 未定義)
import
React,
{
useState,
useEffect,
useRef
} from 'react'
import {
View,
Animated,
TouchableWithoutFeedback,
StyleSheet
} from 'react-native'
import {
interpolateNumber,
interpolateRgb,
} from 'd3-interpolate'
export default d3number = () => {
const [animation] = useState(new Animated.Value(1))
const [position, setPosition] = useState()
const someRef = useRef(null)
const startAnimation = () => {
Animated.timing(animation, {
toValue: 2,
duration: 1500,
}).start()
}
const positionInterpolate = interpolateNumber(0, 300)
useEffect(() => {
animation.addListener(({value}) => {
const pos = positionInterpolate(value)
setPosition(pos)
})
const style = [
styles.box,
{
transform: [
{
translateY: position
}
]
}
]
someRef.setNativeProps({ style })
// console.log(someRef.setNativeProps)
}, [])
return (
<View style={styles.container}>
<TouchableWithoutFeedback onPress={startAnimation}>
<View
style={styles.box}
ref={someRef}
/>
</TouchableWithoutFeedback>
</View>
)
}
更新:這是通過在偵聽器中包含樣式來解決的
if (!someRef.current) {
return;
}
animation.addListener(({value}) => {
const style = [
styles.box,
{
transform: [
{
translateY: positionInterpolate(value)
}
]
}
]
someRef.current.setNativeProps({ style })
})
// console.log(someRef.setNativeProps)
}, [someRef.current])
根據文檔 [1] ref 的值保持在ref.current
。 所以你需要運行someRef.current.setNativeProps
。
這就是說你useEffect
代碼會出現問題,因為someRef
將被設置為null
的,當你第一次渲染useEffect
運行。 您必須將someRef.current
添加到useEffect
依賴項數組,以便在someRef
更新時someRef
效果,並添加一個條件以在someRef.current
為null
時不調用someRef.current.setNativeProps
。 您可能想要跳過整個useEffect
主體,除非someRef.current
不為null
。
useEffect(() => {
if (!someRef.current) {
return;
}
animation.addListener(({value}) => {
const pos = positionInterpolate(value)
setPosition(pos)
})
const style = [
styles.box,
{
transform: [
{
translateY: position
}
]
}
]
someRef.current.setNativeProps({ style })
}, [someRef.current]) # note the addition of `someRef.current` here so the effect runs again when the ref is set
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