PanResponder 中的 ScrollView

Question

我正在使用 React-Native 中的滑动来实现我自己的选项卡导航器。它工作正常，但是当我的一个选项卡中有一个 ScrollView 时，它似乎坏了。左右滑动以更改选项卡工作正常，并且在滚动视图中向下和向上滚动。当我单击拖动滚动视图然后横向移动而不释放滑动时，它会中断。然后标签系统只是重置为第一个标签。

我做了一个 hack，当滚动视图滚动时，我禁止从选项卡内部滑动。这可行，但感觉是一个糟糕的解决方案，因为标签内容必须知道它在标签内。

import React, { Component, PropTypes } from 'react';
import { connect } from 'react-redux';
import { View, Animated, Dimensions, PanResponder } from 'react-native';
import Immutable from 'immutable';
import Tab1 from './Tab1';
import Tab2 from './Tab2';
import ScrollViewTab from './ScrollViewTab';


@connect(
    state => ({
        tabs: state.tabs
    })
)

export default class Tabs extends Component {
    static propTypes = {
        tabs: PropTypes.instanceOf(Immutable.Map).isRequired,
        dispatch: PropTypes.func.isRequired
    };
    constructor(props) {
        super(props);
        this.justLoaded = true;
        this.state = {
            left: new Animated.Value(0),
            tabs: [{ // Tabs must be in order, despite index.
                name: 'tab1',
                component: <Tab1 setTab={this.setTab} />,
                index: 0
            }, {
                name: 'tab2',
                component: <Tab2 setTab={this.setTab} />,
                index: 1
            }, {
                name: 'scrollViewTab',
                component: <ScrollViewTab setTab={this.setTab} />,
                index: 2
            }]
        };
        this.getIndex = this.getIndex.bind(this);
    }
    componentWillMount() {
        this.panResponder = PanResponder.create({
            onMoveShouldSetResponderCapture: () => true,
            onMoveShouldSetPanResponderCapture: (evt, gestureState) => {
                if (Math.abs(gestureState.dx) > 10) {
                    return true;
                }
                return false;
            },
            onPanResponderGrant: () => {
                this.state.left.setOffset(this.state.left._value);
                this.state.left.setValue(0);
            },
            onPanResponderMove: (e, gestureState) => {
                if (this.isSwipingOverLeftBorder(gestureState) ||
                    this.isSwipingOverRightBorder(gestureState)) return;
                Animated.event([null, {
                    dx: this.state.left
                }])(e, gestureState);
            },
            onPanResponderRelease: (e, gestureState) => {
                this.state.left.flattenOffset();

                if (this.isSwipingOverLeftBorder(gestureState) ||
                    this.isSwipingOverRightBorder(gestureState)) {
                    return;
                }

                Animated.timing(
                    this.state.left,
                    { toValue: this.calcX(gestureState) }
                ).start();
            }
        });
    }
    componentDidMount() {
        this.justLoaded = false;
    }
    getStyle() {
        const oldLeft = this.state.left;
        let left = 0;
        const screenWidth = Dimensions.get('window').width;
        // Set tab carouselle coordinate to match the selected tab.
        this.state.tabs.forEach((tab) => {
            if (tab.name === this.props.tabs.get('tab')) {
                left = -tab.index * screenWidth;
            }
        });


        if (this.justLoaded) {
            Animated.timing(
                this.state.left,
                { toValue: left,
                    duration: 0
                }
            ).start();

            return { transform: [{ translateX: oldLeft }], flexDirection: 'row', height: '100%' };
        }
        Animated.timing(
                this.state.left,
            { toValue: left
            }
            ).start();
        return { transform: [{ translateX: oldLeft }], flexDirection: 'row', height: '100%' };
    }
    getIndex(tabN) {
        let index = 0;

        this.state.tabs.forEach((tab) => {
            if (tab.name === tabN) {
                index = tab.index;
            }
            return tab;
        });

        return index;
    }
    setTab(tab, props) {
        this.navProps = props;
        this.props.dispatch({ type: 'SET_TAB', tab });
    }
    isSwipingOverLeftBorder(gestureState) {
        return (this.props.tabs.get('tab') === this.state.tabs[0].name &&
                gestureState.dx > 0);
    }
    isSwipingOverRightBorder(gestureState) {
        return (this.props.tabs.get('tab') === this.state.tabs[this.state.tabs.length - 1].name &&
                gestureState.dx < 0);
    }
    calcX(gestureState) {
        const screenWidth = Dimensions.get('window').width;
        const activeTab = this.getIndex(this.props.tabs.get('tab'));
        let coord = 0;

        if (gestureState.dx > screenWidth * 0.2) {
            coord = (activeTab * screenWidth) - screenWidth;
        } else if (gestureState.dx < -(screenWidth * 0.2)) {
            coord = (activeTab * screenWidth) + screenWidth;
        } else {
            coord = activeTab * screenWidth;
        }

        this.updateTab(-coord, screenWidth);

        return -coord;
    }
    updateTab(coord, screenWidth) {
        // Update current tab according to location and screenwidth
        this.state.tabs.forEach((tab) => {
            if (coord === -tab.index * screenWidth) {
                this.props.dispatch({ type: 'SET_TAB', tab: tab.name });
            }
        });
    }
    render() {
        return (
          <View
            style={{ flex: 1 }}
          >
            <Animated.View
              style={this.getStyle()}
              {...this.panResponder.panHandlers}
            >
              {this.state.tabs.map(tab => tab.component)}
            </Animated.View>
          </View>
        );
    }
}

Answer 1

尝试使用 onMoveShouldSetResponder 函数，这样它只会在gestureState.dx 远大于gestureState.dy 时水平滑动，如下所示：

onMoveShouldSetResponder: (evt, gestureState) => {
    return Math.abs(gestureState.dx) > Math.abs(gestureState.dy * 3);
},

您还可以在 onPanResponderMove 中有一个函数来跟踪滑动手势的方向，然后在 onPanResponderRelease 中重置，这样当垂直滑动变为水平滑动时，您就不会遇到问题，如下所示：

checkSwipeDirection(gestureState) {
    if( 
        (Math.abs(gestureState.dx) > Math.abs(gestureState.dy * 3) ) &&
        (Math.abs(gestureState.vx) > Math.abs(gestureState.vy * 3) )
    ) {
        this._swipeDirection = "horizontal";
    } else {
        this._swipeDirection = "vertical";
    }
}
canMove() {
    if(this._swipeDirection === "horizontal") {
        return true;
    } else {
        return false;
    }
}

然后像这样使用它：

onMoveShouldSetPanResponder: this.canMove,
onPanResponderMove: (evt, gestureState) => {
    if(!this._swipeDirection) this.checkSwipeDirection(gestureState);

// Your other code here
},
onPanResponderRelease: (evt, gestureState) => {
    this._swipeDirection = null;
}

我在 Medium How I built React Native Tab View 上发现了 Satyajit Sahoo 的一篇很棒的在线文章。它更深入地展示了如何实现自己的标签视图。我建议看一下这篇博文，因为它对我很有帮助。

更新：如果您希望父组件防止子组件成为手势响应器，反之亦然，请查看此处的文档 Gesture Responder Lifecycle。

Answer 2

或者您可以尝试使用我的实用工具react-native-scroll-locky 并通过......！

import RNLocky from "react-native-scroll-locky";

class WhateverClass extends Component {
  constructor(props) {
    super(props);
    this.directionLockPanHandler = new RNLocky(
      RNLocky.Direction.HORIZONTAL, // or RNLocky.Direction.VERTICAL
    );
  }


  render() {
      return (
          <ScrollView
              {...this.directionLockPanHandler.getPanHandlers()}
          >
            <ScrollView>
                ...
            </ScrollView>
          </ScrollView>
      );
  }
}

现在你应用这个的滚动视图，只会响应你想要的方向，他们两个不会再混淆哪个应该响应平移/手势。

Answer 3

在使用代码块的视图控制器中（滚动视图，平移手势），

编写这个函数：

func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
   return true
}

希望对你有帮助。:)