如何使用带有数组的状态挂钩

Question

我无法在 useState 数组中推送数字索引。 我哪里出错了，当我点击它们时，我想推送数字索引吗？ 我正在提取以前的状态数组，然后我推送新的但没有任何反应。 如何在 useState 数组 React 钩子中推送新元素？我的代码不起作用！！ 请有人检查。

Game.js

import { StatusBar } from "expo-status-bar";
import React, { useState } from "react";
import { StyleSheet, Text, View } from "react-native";
import RandomNumber from "./RandomNumber";

export default function Game(props) {
  const [state, setstate] = useState([]);
  let randomNumber = Array.from({ length: props.randomNumberCount }).map(
    () => 1 + Math.floor(10 * Math.random())
  );
  let target = randomNumber
    .slice(0, props.randomNumberCount - 2)
    .reduce((acc, curr) => acc + curr, 0);
  const isNumberSelected = (numberIndex) => {
    return state.indexOf(numberIndex) >= 0;
  };
  const selectNumber = (numberIndex) => {
    setstate((arr) => [...arr, numberIndex]);
  };
  return (
    <View style={styles.container}>
      <Text style={styles.header}>Target Sum Game</Text>
      <Text style={styles.target}>{target}</Text>
      <View style={styles.randomContainer}>
        {randomNumber.map((randomNumber, index) => (
          <RandomNumber
            key={index}
            id={index}
            number={randomNumber}
            isSelected={isNumberSelected(index)}
            onClick={() => selectNumber}
          />
        ))}
      </View>
      <StatusBar style="auto" />
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: "#ddd",
    paddingTop: 30,
  },
  target: {
    fontSize: 30,
    backgroundColor: "#aaa",
    margin: 50,
    marginHorizontal: 70,
    textAlign: "center",
  },
  header: {
    fontSize: 35,
    backgroundColor: "dodgerblue",
    textAlign: "center",
    marginHorizontal: 30,
    marginTop: 50,
  },
  randomContainer: {
    flexDirection: "row",
    flexWrap: "wrap",
    justifyContent: "space-around",
  },
});

随机数.js

import React from "react";
import { StyleSheet, Text, TouchableOpacity } from "react-native";

export default function RandomNumber(props) {
  const handlePress = () => {
    props.onClick(props.id);
  };
  return (
    <TouchableOpacity onPress={handlePress()}>
      <Text style={[styles.random, props.isSelected && styles.selected]}>
        {props.number}
      </Text>
    </TouchableOpacity>
  );
}

const styles = StyleSheet.create({
  random: {
    backgroundColor: "#999",
    width: 100,
    marginHorizontal: 35,
    marginVertical: 25,
    fontSize: 35,
    textAlign: "center",
  },
  selected: {
    opacity: 0.3,
  },
});

Answer 1

你没有调用函数

onClick={() => selectNumber(index)}

Answer 2

您需要更改 onClick 属性并将 randomNumber（或索引取决于您想要做什么）传递给 selectNumber 函数：

// Not sure if you want to pass randonNumber or index but you get the idea
onClick={() => selectNumber(randomNumber)}

Answer 3

<TouchableOpacity onPress={handlePress()}>

应该是

<TouchableOpacity onPress={()=>handlePress()}>

和

() => selectNumber

应该是

() => selectNumber()

请尝试一下

Answer 4

可能会有帮助：

Home.Js

import React, {useState, useEffect} from 'react';
import {StyleSheet, Text, View, TouchableOpacity} from 'react-native';
import RandomNumber from './RandomNumber';

const Home = props => {
  const [state, setstate] = useState([]);

  useEffect(() => {
    console.log('state', state);
  }, [state]);

  let randomNumber = Array.from({length: 10}).map(
    () => 1 + Math.floor(10 * Math.random()),
  );

  let target = randomNumber
    .slice(0, props.randomNumberCount - 2)
    .reduce((acc, curr) => acc + curr, 0);

  const isNumberSelected = numberIndex => {
    return state.indexOf(numberIndex) >= 0;
  };

  const selectNumber = numberIndex => {
    console.log('numberIndex', numberIndex);
    setstate(arr => [...arr, numberIndex]);
  };

  return (
    <View style={styles.container}>
      <Text style={styles.header}>Target Sum Game</Text>
      <Text style={styles.target}>{target}</Text>
      <View style={styles.randomContainer}>
        {randomNumber.map((randomNumber, index) => {
          return (
            <RandomNumber
              key={index}
              id={index}
              number={randomNumber}
              isSelected={isNumberSelected(index)}
              onClick={() => selectNumber(randomNumber)}
            />
          );
        })}
      </View>
    </View>
  );
};

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#ddd',
    paddingTop: 30,
  },
  target: {
    fontSize: 30,
    backgroundColor: '#aaa',
    margin: 50,
    marginHorizontal: 70,
    textAlign: 'center',
  },
  header: {
    fontSize: 35,
    backgroundColor: 'dodgerblue',
    textAlign: 'center',
    marginHorizontal: 30,
    marginTop: 50,
  },
  randomContainer: {},
});

export default Home;

RandomNumber.js

import React from 'react';
import {StyleSheet, Text, View, TouchableOpacity} from 'react-native';

export default function RandomNumber(props) {
  const handlePress = () => {
    props.onClick(props.id);
  };
  return (
    <View style={{}}>
      <TouchableOpacity onPress={() => handlePress()}>
        <Text style={[styles.random, props.isSelected && styles.selected]}>
          {props.number}
        </Text>
      </TouchableOpacity>
    </View>
  );
}

const styles = StyleSheet.create({
  random: {
    backgroundColor: '#999',
    width: 100,
    height: 100,
    marginHorizontal: 35,
    marginVertical: 25,
    fontSize: 35,
    textAlign: 'center',
  },
  selected: {
    opacity: 0.3,
  },
});

输出日志：