[英]Update state from inside a PanResponder
我正在使用 react-native-svg 制作應用程序,但無法從 PanResponder 內部更新組件的 state。
我有一個 < Svg > 元素,其中有一個 < Circle >。 < Circle > 的 position 與名為 originCoords 的變量(一個 state 變量)相關。 我已經使用 PanResponder 來制作它,以便在進行平移手勢時,< Svg >(其中包含 < Circle >)被移動,並且一旦手勢結束,< Svg > 將返回其原始 Z46057FE06FDEDEA636A。
我正在嘗試在平移手勢完成后更改 originCoords,因此,即使 < Svg > 回到原來的 position,< Circle > 仍然保持在其新的 Z4757FE07FD492A8BE60EA6A760EZD68。 但是我很難從 PanResponder 內部的 createPanResponder.js 文件中更改 originCoords 的 state,它只是保持不變,至少在 android 仿真器上是這樣。 任何幫助將非常感激。
這是我的文件:
// MapScreen.js
import React, { useRef, useState } from "react";
import { Animated } from "react-native";
import { Svg, Circle } from "react-native-svg";
import { createPanResponder } from "../services/utils/createPanResponder";
export const MapScreen = () => {
const [originCoords, setOriginCoords] = useState({x: 0, y: 0});
const [circleCoords, setCircleCoords] = useState({x: 20, y: 20});
const pan = useRef(new Animated.ValueXY()).current;
const panResponder = createPanResponder(pan, originCoords, setOriginCoords);
return (
<Animated.View
style={{transform: [{ translateX: pan.x }, { translateY: pan.y }],}}
{...panResponder.panHandlers}
>
<Svg width='300' height='300' style={{ backgroundColor: "blue" }}>
<Circle
cx={`${circleCoords.x - originCoords.x}`}
cy={`${circleCoords.y - originCoords.y}`}
r="5"
stroke="white"
strokeWidth="1"
/>
</Svg>
</Animated.View>
);
};
import { useRef } from "react";
import { PanResponder, Animated } from "react-native";
export const createPanResponder = (pan, originCoords, setOriginCoords) => {
return useRef(
PanResponder.create({
// PanResponder default configs have been removed to be more succint
onPanResponderMove: (evt, gestureState) => {
// sets pan.x and pan.y to equal gesture's deltas
Animated.event([{ x: pan.x }])({ x: gestureState.dx });
Animated.event([{ y: pan.y }])({ y: gestureState.dy });
},
onPanResponderRelease: (evt, gestureState) => {
//resets pan.x and pan.y
Animated.event([{ x: pan.x }])({ x: 0 });
Animated.event([{ y: pan.y }])({ y: 0 });
// PROBLEM IS HERE, setOriginCoords DOESN'T DO ANYTHING
console.log(originCoords); // { x: 0, y: 0 }
const { dx, dy } = gestureState;
setOriginCoords({ ...originCoords, dx, dy });
console.log(originCoords); // { x: 0, y: 0 }
},
})
).current;
};
雖然我沒有看到將這個function
變成 class 組件的失敗原因,但functions
沒有state
,只有類有。 這是我今天從這里和文檔中學到的
constructor(props) {
super(props);
this.pan = new Animated.ValueXY();
this.panResponder = PanResponder.create({
onStartShouldSetPanResponder: (e, state) => false,
onStartShouldSetPanResponderCapture: (e, state) => false,
onMoveShouldSetPanResponder: () => true,
onMoveShouldSetPanResponderCapture: (e, { dx, dy }) => {
if (Math.abs(dx) > 10 || Math.abs(dy) > 10) {
this.state.holding && this.setState({ holding: false });
return true;
} else {
!this.state.holding && this.setState({ holding: true });
return true;
}
},
onPanResponderGrant: (e, gestureState) => {
this.pan.setOffset(this.pan.__getValue());
this.pan.setValue({ x: e.nativeEvent.pageX, y: e.nativeEvent.pageY });
},
onPanResponderMove: (e, gesture) => {
this.pan.setValue({ x: gesture.dx, y: gesture.dy });
/*Animated.event([null, { dx: this.pan.x, dy: this.pan.y }])(
e,
gestureState
);*/
if (Math.abs(gesture.dx) > 10 || Math.abs(gesture.dy) > 10) {
clearTimeout(this.t);
this.state.holding && this.setState({ holding: false });
} else {
!this.state.holding && this.setState({ holding: true });
}
},
onPanResponderRelease: (e, { vx, dx }) => {
this.setState({ holding: false });
const offScreenX = () => {
if (this.props.width < e.nativeEvent.pageX) {
Animated.spring(this.pan.x, {
toValue: this.props.width - 60,
bounciness: 10
}).start();
} else if (0 > e.nativeEvent.pageX) {
Animated.spring(this.pan.x, {
toValue: 0,
bounciness: 10
}).start();
}
};
const offScreenY = () => {
if (this.props.height < e.nativeEvent.pageY) {
Animated.spring(this.pan.y, {
toValue: this.props.height - 60,
bounciness: 10
}).start();
} else if (0 > e.nativeEvent.pageY) {
Animated.spring(this.pan.y, {
toValue: 0,
bounciness: 10
}).start();
}
};
// abs(vx) speed (not velocity) of gesture,
// abs(dx) distance traveled (not displacement)
//if (Math.abs(vx) >= 0.5 || Math.abs(dx) >= 30) {
this.pan.flattenOffset();
//}
if (this.props.width / 2 > e.nativeEvent.pageX) {
if (this.props.height / 2 < e.nativeEvent.pageY) {
offScreenX();
Animated.spring(this.pan.y, {
toValue: this.props.height - 60,
bounciness: 10
}).start();
} else {
offScreenY();
Animated.spring(this.pan.x, {
toValue: 0,
bounciness: 10
}).start();
}
} else {
if (this.props.height / 2 > e.nativeEvent.pageY) {
offScreenX();
Animated.spring(this.pan.y, {
toValue: 0,
bounciness: 10
}).start();
} else {
offScreenY();
Animated.spring(this.pan.x, {
toValue: this.props.width - 60,
bounciness: 10
}).start();
}
}
}
});
this.state = { highAndTight: true, hideOpener: true };
}
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