4

为什么拖动框时nativeEvent我的调用中没有触发回调?Animated.event

我的最终目标是实现逻辑以防止可拖动的手势控制组件离开屏幕,但我无法做到这一点,直到我弄清楚为什么所需的回调永远不会触发。

我为一个组件设置了一个onGestureEvent回调,并在其中传递了一个带有回调的调用(有关如何执行此操作的示例,请参见他们的文档)。<PanGestureHandler />Animated.event()nativeEvent

我知道 nativeEvent 回调没有触发,因为其中的 debug 和 console.log 调用Animated.block()没有向控制台输出任何内容(我正在使用 Expo- debug 链接运行它)。此外,调用中的set(_translateX, translationX)Animate.block()也永远不会执行,否则我希望看到框在拖动它们时移动(而不是在释放触摸时)。

请注意,如果您取消注释以下块,并{ nativeEvent: function... }直接删除它之后的对象,动画将按预期工作:

    {
      nativeEvent: {translationX: _translateX}
    },

我觉得我错过了一些非常简单的东西,但我不知道它是什么。

这是用于调试的博览会链接:https ://snack.expo.io/d8xCeHhtj

这是我的代码:

import React, { Component } from 'react';
import {
  Dimensions,
  StyleSheet,
  Text,
  View,
  Button,
  Animated
} from 'react-native';
import {
  PanGestureHandler,
  ScrollView,
  State,
} from 'react-native-gesture-handler';
const {
  and,
  block,
  clockRunning,
  set,
  Clock,
  cond,
  eq,
  debug,
  Extrapolate,
  max,
  lessThan,
  greaterOrEq,
  Value,
  startClock,
  timing,
  call,
  stopClock,
} = Animated;

function Slider({color, width, height}) {
  const screenWidth = Dimensions.get('window').width;
  const _translateX = new Animated.Value(0);
  const _lastOffset = {x: 0};

  const cmpStyles = StyleSheet.create({
    box: {
      width: width,
      height: height,
      alignSelf: 'center',
      backgroundColor: color,
      margin: 30,
      zIndex: 200,
      color: color,
      transform: [
        {translateX: _translateX},
      ],
    },
  });

  const _onGestureEvent = Animated.event(
        [
  // Uncomment this block to see the original animation
    /*
            {
                nativeEvent: {translationX: _translateX}
            },
    */
  // Comment the following object when uncommenting the previous section
            {
                nativeEvent: function({ translationX, absoluteX }) {
                    return block([
                        debug('x', translationX),
                        call([], () => console.log('the code block was executed')),
                        set(_translateX, translationX),
                    ])
                }
            },
  // ------------------------------
        ],
        {
            useNativeDriver: true,
            listener: (event, gestureState) => {
                const {absoluteX, translationX} = event.nativeEvent;
                //console.log('translationX' + translationX);
                //console.log('dest' + _translateX._value);
            }
        }
  );
  const _onHandlerStateChange = event => {
    const {
      oldState,
      translationX,
      absoluteX,
    } = event.nativeEvent;
    if (oldState === State.ACTIVE) {
      //if (absoluteX + translationX > screenWidth) {
      //console.log("translationX: " + translationX);
      //console.log("screenWidth" + screenWidth);

      // Set the slider to correct position when gesture is released
      _lastOffset.x += translationX;
      _translateX.setOffset(_lastOffset.x);
      _translateX.setValue(0);
    }
  };

  return (
    <PanGestureHandler
      onGestureEvent={_onGestureEvent}
      onHandlerStateChange={_onHandlerStateChange}
            >
      <Animated.View style={cmpStyles.box} />
    </PanGestureHandler>
  );
}

export default function Example() {
  const width = 60;
  const height = 60;

  return (
    <View style={styles.scrollView}>
      <Slider color={'red'} width={width} height={height} />
      <Slider color={'blue'} width={width} height={height} />
      <Slider color={'green'} width={width} height={height} />
      <Slider color={'orange'} width={width} height={height} />
    </View>
  );
}

const styles = StyleSheet.create({
  scrollView: {
    flex: 1,
    marginTop: 120,
  },
})

谢谢您的帮助。

4

2 回答 2

2

您可以使用来自react-native-reanimated 的Animated

因为当我们从react-native导入Animated时 nativeEvent 调用不起作用

import React, { Component } from "react";
import { Dimensions, StyleSheet, Text, View, Button } from "react-native";
import { PanGestureHandler, State } from "react-native-gesture-handler";
import Animated from "react-native-reanimated";

const {
  and,
  block,
  clockRunning,
  set,
  Clock,
  cond,
  eq,
  debug,
  Extrapolate,
  max,
  lessThan,
  greaterOrEq,
  Value,
  startClock,
  timing,
  call,
  stopClock,
  event,
} = Animated;

function Slider({ color, width, height }) {
  const screenWidth = Dimensions.get("window").width;
  const _translateX = new Value(0);
  const _lastOffset = { x: 0 };

  const cmpStyles = StyleSheet.create({
    box: {
      width: width,
      height: height,
      alignSelf: "center",
      backgroundColor: color,
      margin: 30,
      zIndex: 200,
      color: color,
      transform: [{ translateX: _translateX }],
    },
  });
  const _onGestureEvent = event(
    [
      // Uncomment this block to see the original animation
      /*
            {
                nativeEvent: {translationX: _translateX}
            },
    */
      // Comment the following object when uncommenting the previous section
      {
        nativeEvent: ({ translationX: x, translationY: y, state }) =>
          block([
            // debug('x', _translateX),
            call([], () => console.log("the code block was executed")),
            set(_translateX, x),
          ]),
      },
    ],
    // ------------------------------
    {
        useNativeDriver: true,
        listener: (event, gestureState) => {
            const {absoluteX, translationX} = event.nativeEvent;
            //console.log('translationX' + translationX);
            //console.log('dest' + _translateX._value);
        }
    }
  );
  const _onHandlerStateChange = (event) => {
    const { oldState, translationX, absoluteX } = event.nativeEvent;
    if (oldState === State.ACTIVE) {
      //if (absoluteX + translationX > screenWidth) {
      //console.log("translationX: " + translationX);
      //console.log("screenWidth" + screenWidth);

      // Set the slider to correct position when gesture is released
      _lastOffset.x += translationX;
      _translateX.setValue(_lastOffset.x);
    }
  };

  return (
    <PanGestureHandler
      onGestureEvent={_onGestureEvent}
      onHandlerStateChange={_onHandlerStateChange}
    >
      <Animated.View style={cmpStyles.box} />
    </PanGestureHandler>
  );
}

export default function Example() {
  const width = 60;
  const height = 60;

  return (
    <View style={styles.scrollView}>
      <Slider color={"red"} width={width} height={height} />
      <Slider color={"blue"} width={width} height={height} />
      <Slider color={"green"} width={width} height={height} />
      <Slider color={"orange"} width={width} height={height} />
    </View>
  );
}

const styles = StyleSheet.create({
  scrollView: {
    flex: 1,
    marginTop: 120,
  },
});

于 2020-05-12T12:46:59.647 回答
-1

编写处理函数,如

handleSctoll = (e) => {
   console.log(e.nativeEvent.contentOffset.y);
}

你可以像这样添加监听器

Animated.event(
   [{ nativeEvent: { contentOffset: { y: this.state.scrollY } } }],
   { listener: (event) => this.handleSctoll(event) }
)
于 2020-05-02T07:15:35.267 回答