反应本机PanResponder

Question

I am trying to use the PanResponder in React Native.

Very simple - I have 2 elements:

1. A View, which is the width of the screen and a height of 100.
2. An Animated.View, which is 50 wide, 50 high, and 25 borderRadius so it is a circle. The circle is sitting inside the main view.

I want to effectively be able to drag the circle across the screen. Could someone help me out?

Heres is my code thus far :

import React from 'react';
import { Animated, Dimensions, PanResponder, StyleSheet, View } from 'react-native';



export class MySlider extends React.Component {
    constructor(props) {
        super(props);
        this.state = {
            pan: new Animated.ValueXY()
        };
    }

    _panResponder = PanResponder.create({
            // Ask to be the responder:
            onStartShouldSetPanResponder: (evt, gestureState) => true,
            onStartShouldSetPanResponderCapture: (evt, gestureState) => true,
            onMoveShouldSetPanResponder: (evt, gestureState) => true,
            onMoveShouldSetPanResponderCapture: (evt, gestureState) => true,

            onPanResponderGrant: (evt, gestureState) => {
                this.state.pan.setValue({x: 0, y: 0});
                return true
            },
            onPanResponderMove: (evt, gestureState) => {
                Animated.event([null, {dx: this.state.pan.x, dy: this.state.pan.y}])
                return true
            },
            onPanResponderTerminationRequest: (evt, gestureState) => true,
            onPanResponderRelease: (evt, gestureState) => {
                return true
            },
            onPanResponderTerminate: (evt, gestureState) => {
                return true
            },
            onShouldBlockNativeResponder: (evt, gestureState) => {
                return true;
            },
        });

    render() {
        let { pan } = this.state;
        let [translateX, translateY] = [pan.x, pan.y];
        const styles = StyleSheet.create({
            mover: {
                transform: [{translateX:translateX}, {translateY:5}],
                height: 50,
                width: 50,
                borderRadius: 25,
                backgroundColor: 'blue'
            },
            holder: {
                height: 100,
                width: Dimensions.get('window').width,
                backgroundColor: 'yellow'
            }
        });
        return (
            <View style={styles.holder}>
                <Animated.View style={styles.mover} {...this._panResponder.panHandlers}/>   
            </View>
            )
    }
}

Answer 1

i changed your code a bit so try this

 import React,{Component} from 'react' import { PanResponder, View, Animated, StyleSheet, Dimensions } from 'react-native' export default class MySlider extends React.Component { constructor(props) { super(props); this.state = { pan: new Animated.ValueXY() }; this._panResponder = PanResponder.create({ onStartShouldSetPanResponder : () => true, onPanResponderGrant: (e, gestureState) => { this.setState({isAddNewSession:true}) }, onPanResponderMove : Animated.event([null,{ //Step 3 dx : this.state.pan.x, dy : this.state.pan.y }]), onPanResponderRelease : (e, gesture) => { this.setState({isAddNewSessionModal:true}, ) Animated.spring( this.state.pan, {toValue:{x:0,y:0}} //To default position you can delete this animated.spring() ).start(); this.setState({isAddNewSession:false}) }, }); } render() { let { pan } = this.state; let [translateX, translateY] = [pan.x, pan.y]; const styles = StyleSheet.create({ mover: { transform: [{translateX:translateX}, {translateY:translateY}], height: 50, width: 50, position:'absolute', top:0, borderRadius: 25, zIndex:20, backgroundColor: 'blue' }, holder: { height: 100, width: Dimensions.get('window').width, backgroundColor: 'yellow' } }); return ( <View style={styles.holder}> <Animated.View style={styles.mover} {...this._panResponder.panHandlers}/> </View> ) } } 

let me know if its work or not...

Answer 2

Yes that worked. I copied and pasted your class in place of my class and now it works. I can drag it in two dimensions and when I release it goes back to where it began. Thank you.

what is this.setState({isAddNewSession:true}) , this.setState({isAddNewSessionModal:true}) and this.setState({isAddNewSession:false}) ??

Also, when I delete the Animated.Spring, I can drag and drop the circle - but when I drag it a second time, The circle begins from the original spot. Any suggestions on how to pick up where I left off? I tried replacing dx and dy with moveX and moveY but it hasn't worked. I also tried to store the old value in a variable but it is complicated because it is an Animated value and a javascript object.