自定义方法时最好不要向下面哪种定义

customPressHandler(){
    //不建议这样定义方法
    alert('你按下了按钮');
}

最好使用属性来定义，这样会把this绑定到这个方法上

customPressHandler =()=>{
    alert('你按下了按钮'+this.state.status);
};

完整代码：

import React, {Component} from "react";
import {Modal, Text, StyleSheet, TouchableHighlight, TouchableOpacity, View} from "react-native";

export default class ModalExample extends Component {
    state = {
        modalVisible: false,
        status: 1
    };

    setModalVisible(visible) {
        this.setState({modalVisible: visible});
    }

    /*customPressHandler(){
        //不建议这样定义方法
        alert('你按下了按钮');
    }*/
    customPressHandler = () => {
        //自定义的方法，请使用属性来定义,这里自定的把this绑定到这个方法上
        alert('你按下了按钮' + this.state.status);
    };

    render() {
        return (
            <View style={{marginTop: 22}}>
                <Modal
                    animationType="slide"
                    transparent={false}
                    presentationStyle="overFullScreen"
                    visible={this.state.modalVisible}
                    onRequestClose={() => {
                        alert("Modal has been closed.");
                    }}
                >
                    <View style={{marginTop: 22}}>
                        <View>
                            <Text>Hello World!</Text>

                            <TouchableOpacity
                                onPress={() => {
                                    this.setModalVisible(!this.state.modalVisible);
                                }}
                            >
                                <Text>Hide Modal</Text>
                            </TouchableOpacity>
                        </View>
                        <Text>这是测试内容</Text>
                    </View>
                </Modal>

                <TouchableHighlight
                    onPress={() => {
                        this.setModalVisible(true);
                    }}
                >
                    <Text>Show Modal</Text>
                </TouchableHighlight>
                <View style={{flex: 1, justifyContent: 'center', alignItems: 'center'}}>
                    <TouchableOpacity
                        style={styles.button}
                        onPress={this.customPressHandler}>
                        <Text style={styles.buttonText}>确定</Text>
                    </TouchableOpacity>
                </View>
            </View>
        );
    }
}

const styles = StyleSheet.create({
    button: {
        width: 150,
        height: 40,
        borderRadius: 20,
        backgroundColor: 'green',
        justifyContent: 'center',
        overflow: 'hidden'
    },
    buttonText: {
        textAlign: 'center'
    }
});