reactjs - 如何使百分比按钮在 react-native 中工作

Question

编辑

能够让它工作，但现在当我点击“税收”按钮时，它说结果是 NaN。我该如何解决？

用 react-native 构建一个小型计算应用程序。除了税收按钮外，所有按钮都有效。对于 Tax 按钮，我需要它在两个数字的加法、减法、乘法或除法的结果中加上 12%。有人可以帮助我了解我在这里做错了什么吗？尝试在线查找，但无法找到解决方案。如果有人指出错误，我们将非常高兴。

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

export default class Counter extends React.Component {

state = {
    num: 0,
}

inp1 = 0;
inp2 = 0;

handleSubtract = () => {
    this.setState({
        num:this.inp1-this.inp2
    })
}

handleAdd = () => {
    this.setState({
        num: this.inp1 + this.inp2
    })
}

handleDivide = () => {
    this.setState({
        num: this.inp1 / this.inp2
    })
}

handleMultiply = () => {
    this.setState({
        num: this.inp1 * this.inp2
    })
}

handleTax = () => {

    var newNum = this.num / 100 * 12;

    this.setState({
        num: newNum
    })
}

handleNum1 = (text) => {
    this.inp1 = parseInt(text);
}

handleNum2 = (text) => {
    this.inp2 = parseInt(text);
}

render() {
    return (
        <View style={styles.flexBox}>
            <Text style={styles.flexTitle}>Hi, welcome to my app!</Text>
            <View style={styles.inpBox}>
                <TextInput
                    style={[styles.inps, {marginRight: 10}]}
                    placeholder="Num1"
                    keyboardType="phone-pad"
                    onChangeText={this.handleNum1}
                />
                <TextInput
                    style={styles.inps}
                    placeholder="Num2"
                    keyboardType="phone-pad"
                    onChangeText={this.handleNum2}
                />
            </View>
            <View style={styles.butBox}>
                <View style={styles.button}>
                    <Button
                        onPress={this.handleSubtract}
                        title="Subtract"
                    />
                </View>
                <View style={styles.button}>
                    <Button
                        onPress={this.handleAdd}
                        title="Add"
                    />
                </View>
                <View style={styles.button}>
                    <Button
                        onPress={this.handleMultiply}
                        title="Multiply"
                    />
                </View>
                <View style={styles.button}>
                    <Button
                        onPress={this.handleDivide}
                        title="Divide"
                    />
                </View>
                <View style={[styles.button, {height: 65, width: 65}]}>
                    <Button
                        onPress={this.handleTax}
                        title="Tax"
                        color="#f00"
                />
                </View>
            </View>
            <Text style={styles.numBox}>
                {this.state.num}
            </Text>
        </View>
    );
}
}

const styles = StyleSheet.create({
flexBox: {
    flex: 1,
    flexDirection: "column",
    justifyContent: "center",
    alignItems: "center",
},

flexTitle: {
    padding: 10,
},

inpBox: {
    flexDirection: "row",
},

inps: {
    width: "20%",
    height: 50,
    textAlign: "center",
},

butBox: {
    flexDirection: "row",
    width: "100%",
    alignItems: "center",
},

button: {
    width: "20%",
    height: 50,
},

numBox: {
    padding: 20,
    fontSize: 32,
}
});

Answer 1

您的代码中只有一个错误可以使其按您希望的方式工作。在你的函数中 handleTax

您指的是错误的 num。

而不是 this.num 像这样引用它 - this.state.num

将如下所示:

handleTax = () => {
    var newNum = this.state.num / 100 * 12;

    this.setState({
        num: newNum
    });
}

这将消除 NaN 结果。

要进行正确的税收计算，如下所示:

var newNum = this.state.num + this.state.num * 0.12;