React Native【实战范例】同步跟随滚动

最终效果

实现原理

主动滚动区触发滚动事件，原生监听滚动值的变化，并用动画的方式实时同步到跟随滚动区

技术要点

• 使用 Animated.ScrollView

• 使用动画变量

  const scrollY = useRef(new Animated.Value(0)).current;
  

• 主动滚动触发 onScroll，用 Animated.event 实现原生绑定

            onScroll={Animated.event(
              [
                {
                  nativeEvent: {
                    contentOffset: { y: scrollY },
                  },
                },
              ],
              { useNativeDriver: true }
            )}
  

• 跟随滚动

  transform: [{ translateY: Animated.multiply(-1, scrollY) }],
  

范例代码

import React, { useRef } from "react";
import { Animated, StyleSheet, View } from "react-native";
const colors = ["red", "green", "blue", "yellow", "orange"];
export default function Demo() {
  const scrollY = useRef(new Animated.Value(0)).current;
  const viewList = () => {
    const array = [
      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
    ];
    return (
      <>
        {array.map((item, index) => (
          <View
            key={item}
            style={{
              width: 60,
              height: 100,
              backgroundColor: colors[index % 5],
            }}
          />
        ))}
      </>
    );
  };
  return (
    <View style={styles.root}>
      <View style={styles.leftLayout}>
        <Animated.View
          style={{
            width: 60,
            transform: [{ translateY: Animated.multiply(-1, scrollY) }],
          }}
        >
          {viewList()}
        </Animated.View>
      </View>
      <View style={styles.rightLayout}>
        <Animated.ScrollView
          showsVerticalScrollIndicator={false}
          onScroll={Animated.event(
            [
              {
                nativeEvent: {
                  contentOffset: { y: scrollY },
                },
              },
            ],
            { useNativeDriver: true }
          )}
        >
          {viewList()}
        </Animated.ScrollView>
      </View>
    </View>
  );
}
const styles = StyleSheet.create({
  root: {
    width: "100%",
    height: "100%",
    flexDirection: "row",
    justifyContent: "center",
  },
  leftLayout: {
    width: 60,
    backgroundColor: "#00FF0030",
    flexDirection: "column",
  },
  rightLayout: {
    width: 60,
    height: "100%",
    backgroundColor: "#0000FF30",
    marginLeft: 100,
  },
});