reactjs - 如何将拖动 View 绑定(bind)到ScrollView项目中？

Question

我创建了具有三个 View 的ScrollView。我想将拖动的 View 绑定(bind)到 ScrollView 内部，其余未拖放的 View 应保留在 ScrollView 外部。怎么可能。

查看 GIF:我想在 ScrollView 中添加draggableView。

代码:

import React, { Component } from 'react';
import {
  StyleSheet,
  View,
  Text,
  PanResponder,
  Animated,
  Easing,
  Dimensions,
  Platform,
  TouchableOpacity,
  ScrollView,
} from 'react-native';
import Carousel from 'react-native-snap-carousel';


let CIRCLE_RADIUS = 36;
let Window = Dimensions.get('window');
const instructions = Platform.select({
  ios: 'Press Cmd+R to reload,\n' +
    'Cmd+D or shake for dev menu',
  android: 'Double tap R on your keyboard to reload,\n' +
    'Shake or press menu button for dev menu',
});

export default class App extends Component<{}> {
  constructor(props){
    super(props);

    this.dataDrag      =  [1,2,3,4],
    this.pan = this.dataDrag.map( () => new Animated.ValueXY() );

    this.state = {
        showDraggable   : true,
        dropZoneValues  : null,
        entries : ['Apple1' , 'Apple2', 'Apple3']
    };
}

getPanResponder(index) {
    return PanResponder.create({
        onStartShouldSetPanResponder: () => true,
        onPanResponderMove              : Animated.event([null,{
            dx  : this.pan[index].x,
            dy  : this.pan[index].y
        }]),
        onPanResponderRelease           : (e, gesture) => {
            if(this.isDropZone(gesture)){
                this.setState({
                    showDraggable : false
                });
            }else{
                Animated.spring(
                    this.pan[index],
                    {toValue:{x:0,y:0}}
                ).start();
            }
        }
    });
}

isDropZone(gesture){
    var dz = this.state.dropZoneValues;
    return gesture.moveY > dz.y && gesture.moveY < dz.y + dz.height;
}

setDropZoneValues(event){
  console.log('event.nativeEvent.layout', event.nativeEvent.layout);
    this.setState({
        dropZoneValues : event.nativeEvent.layout
    });
}

_renderItem ({item, index}) {
    return (
        <View style={{width: Dimensions.get('window').width - 100 , height : 150 , backgroundColor : 'red' , marginLeft : 50 , marginRight : 50}}>
            <Text style={{color : 'black' , marginTop : 20}}>{item}</Text>
        </View>
    );
}

render(){
    return (
        <View style={styles.mainContainer}>

            <ScrollView>
              <View onLayout={this.setDropZoneValues.bind(this)}
                  style={[styles.dropZone , {marginTop : 10}]}>
              </View>
              <View onLayout={this.setDropZoneValues.bind(this)}
                  style={[styles.dropZone , {marginTop : 10}]}>
              </View>
              <View onLayout={this.setDropZoneValues.bind(this)}
                  style={[styles.dropZone , {marginTop : 10}]}>
              </View>
            </ScrollView>


            {this.dataDrag.map((d, index) => (
                <Animated.View
                    key={index}
                    {...this.getPanResponder(index).panHandlers}
                    style={[styles.draggableContainer, this.pan[index].getLayout(), styles.circle]}>
                    <Text style={styles.text}>Drag {index}</Text>
                </Animated.View>
            ))}
        </View>
    );
  }
}

let styles = StyleSheet.create({
    mainContainer: {
        flex    : 1
    },
    dropZone    : {
        height  : 100,
        backgroundColor:'#2c3e50'
    },
    text        : {
        marginTop   : 25,
        marginLeft  : 5,
        marginRight : 5,
        textAlign   : 'center',
        color       : '#fff'
    },
    draggableContainer: {
        position    : 'absolute',
        marginTop         : Window.height/2 - CIRCLE_RADIUS,
        marginLeft        : Window.width/2 - CIRCLE_RADIUS,
    },
    circle      : {
        backgroundColor     : '#1abc9c',
        width               : CIRCLE_RADIUS*2,
        height              : CIRCLE_RADIUS*2,
        borderRadius        : CIRCLE_RADIUS
    },
});

Answer 1

其基本思想是创建两个数组，通过从一个结构中删除并复制到另一个结构来模拟移动效果。

逐步:

1. 创建两个数组

   this.state = {
       dataDrag: [...this.dataDrag],
       dataDragged: [],
   };
   

2. OnPanResponderRelease，移至新数组。

   onPanResponderRelease           : (e, gesture) => {
       if(this.isDropZone(gesture)){
           let idx = this.state.dataDrag.indexOf(index+1);
           this.setState({
               showDraggable : false,
               dataDrag: [ ...this.state.dataDrag.slice(0, idx), ...this.state.dataDrag.slice(idx+1, this.state.dataDrag.length-1) ],
               dataDragged: [...this.state.dataDragged, this.state.dataDrag[idx]],
           });
       }
   

3. 创建两组 Animated.View，一组在 ScollView 内部，一组在其外部。

最终代码:

import React, { Component } from 'react';
import {
  StyleSheet,
  View,
  Text,
  PanResponder,
  Animated,
  Easing,
  Dimensions,
  Platform,
  TouchableOpacity,
  ScrollView,
} from 'react-native';

let CIRCLE_RADIUS = 36;
let Window = Dimensions.get('window');

export class App extends Component<{}> {
  constructor(props){
    super(props);

    this.dataDrag      =  [1,2,3,4],
    this.pan = this.dataDrag.map( () => new Animated.ValueXY() );

    this.state = {
        showDraggable   : true,
        dropZoneValues  : null,
        entries : ['Apple1' , 'Apple2', 'Apple3'],
        dataDrag: [...this.dataDrag],
        dataDragged: [],
    };
}

getPanResponder(index) {
    return PanResponder.create({
        onStartShouldSetPanResponder: () => {
            return true;
        },
        onPanResponderMove              : Animated.event([null,{
            dx  : this.pan[index].x,
            dy  : this.pan[index].y
        }]),
        onPanResponderRelease           : (e, gesture) => {
            if(this.isDropZone(gesture)){
                let idx = this.state.dataDrag.indexOf(index+1);
                this.setState({
                    showDraggable : false,
                    dataDrag: [ ...this.state.dataDrag.slice(0, idx), ...this.state.dataDrag.slice(idx+1, this.state.dataDrag.length-1) ],
                    dataDragged: [...this.state.dataDragged, this.state.dataDrag[idx]],
                });
            }else{
                Animated.spring(
                    this.pan[index],
                    {toValue:{x:0,y:0}}
                ).start();
            }
        }
    });
}

isDropZone(gesture){
    var dz = this.state.dropZoneValues;
    return gesture.moveY > dz.y && gesture.moveY < dz.y + dz.height;
}

setDropZoneValues(event){
    this.setState({
        dropZoneValues : event.nativeEvent.layout
    });
}

_renderItem ({item, index}) {
    return (
        <View style={{width: Dimensions.get('window').width - 100 , height : 150 , backgroundColor : 'red' , marginLeft : 50 , marginRight : 50}}>
            <Text style={{color : 'black' , marginTop : 20}}>{item}</Text>
        </View>
    );
}

render(){
    return (
        <View style={styles.mainContainer}>

            <ScrollView>
              <View onLayout={this.setDropZoneValues.bind(this)}
                  style={[styles.dropZone , {marginTop : 10}]}>
              </View>
              <View onLayout={this.setDropZoneValues.bind(this)}
                  style={[styles.dropZone , {marginTop : 10}]}>
              </View>
              <View onLayout={this.setDropZoneValues.bind(this)}
                  style={[styles.dropZone , {marginTop : 10}]}>
              </View>

            {this.state.dataDragged.map((d, index) => (
                <Animated.View
                    key={d-1}
                    style={[styles.draggableContainer, this.pan[d-1].getLayout(), styles.circle]}>
                    <Text style={styles.text}>Drag {d-1}</Text>
                </Animated.View>
              ))}

            </ScrollView>

            {this.state.dataDrag.map((d, index) => (
                <Animated.View
                    key={d-1}
                    {...this.getPanResponder(d-1).panHandlers}
                    style={[styles.draggableContainer, this.pan[d-1].getLayout(), styles.circle]}>
                    <Text style={styles.text}>Drag {d-1}</Text>
                </Animated.View>
              ))}



        </View>
    );
  }
}

let styles = StyleSheet.create({
    mainContainer: {
        flex    : 1
    },
    dropZone    : {
        height  : 100,
        backgroundColor:'#2c3e50'
    },
    text        : {
        marginTop   : 25,
        marginLeft  : 5,
        marginRight : 5,
        textAlign   : 'center',
        color       : '#fff'
    },
    draggableContainer: {
        position    : 'absolute',
        marginTop         : Window.height/2 - CIRCLE_RADIUS,
        marginLeft        : Window.width/2 - CIRCLE_RADIUS,
    },
    circle      : {
        backgroundColor     : '#1abc9c',
        width               : CIRCLE_RADIUS*2,
        height              : CIRCLE_RADIUS*2,
        borderRadius        : CIRCLE_RADIUS
    },
});

结果: