我在谷歌上搜索了一段时间,但没有找到明确的答案,我的问题是我有一个搜索屏幕,上面有一个文本输入和一个 Select 输入和按钮,所以我在输入文本后点击按钮,调用API后结果就会显示出来.但问题是,当我导航到不同的屏幕并返回到搜索屏幕时,结果仍然存在.我需要它是空的输入文本域和结果.

我try 了许多"解决方案",但都没有奏效.我使用了useEffect()挂钩,但它不起作用,我试图将记录数组设置为空,但没有起作用

以下是我的搜索屏幕代码:

import {
    StyleSheet,
    View,
    ActivityIndicator,
    FlatList,
    Button,
} from 'react-native';
import React, { useState, useEffect } from 'react';
import AppTextInput from '../components/AppTextInput';
import Card from '../components/Card';

import colors from '../config/colors';

import axios from 'axios';
import { baseApiUrl, apikey } from '../api/config/apiLinks';
import AppPicker from '../components/AppPicker';
import AppText from '../components/AppText';
import { openBrowserAsync } from 'expo-web-browser';

const options = [
    { value: 'news', label: 'News' },
    { value: 'videos', label: 'Videos' },
    { value: 'documentaries', label: 'Documentaries' },
    { value: 'channels', label: 'Channels' },
];

export default function SearchScreen({ navigation }) {
    const [selected, setSelected] = useState(options[0]);
    const [input, setInput] = useState();

    const [resultRecords, setResultRecords] = useState([]);
    const [totalPages, setTotalPages] = useState();
    const [currentPage, setCurrentPage] = useState(1);
    const [errorMessage, setErrorMessage] = useState('');
    const [isLoading, setIsLoading] = useState(false);
    const [attachEnd, setAttachEnd] = useState(false);

    const url =
        baseApiUrl +
        '/search/search-get.php?' +
        apikey +
        '&category=' +
        selected.value +
        '&q=' +
        input +
        '&page=' +
        currentPage +
        '&count=15';

    const loadSearchResult = () => {
        setIsLoading(true);
        console.log('selected: ', selected.value);
        console.log('url: ', url);

        axios
            .get(url)
            .then((response) => {
                setErrorMessage(0);
                console.log(response);
                setTotalPages(response.data.totalPages);
                if (attachEnd) {
                    setResultRecords([...resultRecords, ...response.data.data]);
                } else {
                    setResultRecords(response.data.data);
                }
                setIsLoading(false);
                setAttachEnd(false);
                console.log('records: ', resultRecords);
            })
            .catch((error) => {
                if (error.response.status == 404) {
                    setErrorMessage('Results not found!');
                }
                setIsLoading(false);
                console.log(error.response);
            });
    };

    const onInputChange = (text) => {
        if (text != '') {
            setInput(text);
            console.log('onInputChange: ', input);
        }
    };

    const renderLoader = () => {
        return isLoading ? (
            <View style={styles.loaderStyle}>
                <ActivityIndicator size="large" color="#aaa" />
            </View>
        ) : null;
    };

    //this useEffect execute the function only once
    useEffect(() => {
        setResultRecords([]);
        setInput('');
    }, [navigation]);

    return (
        <View style={styles.container}>
            <View style={styles.innerContainer}>
                <AppTextInput
                    placeholder="Search..."
                    icon="magnify"
                    onFieldChange={onInputChange}
                />
            </View>
            <View style={styles.innerContainer}>
                <AppPicker
                    selectedItem={selected}
                    onSelectItem={(item) => setSelected(item)}
                    items={options}
                    icon="apps"
                    placeholder="Category"
                />
            </View>
            <View style={styles.button}>
                <Button title="Search" onPress={loadSearchResult} />
            </View>

            <View style={styles.results}>
                {errorMessage == '' && (
                    <FlatList
                        data={resultRecords}
                        keyExtractor={(records) => records.title}
                        renderItem={({ item }) => (
                            <Card
                                title={item.title}
                                feedName={item.feedName}
                                date={item.pubDate}
                                imageUrl={item.image}
                                onPress={() => {
                                    console.log('selectedOnPress: ', selected);
                                    console.log('browser: ', item.link);
                                    if (selected.value == 'news') {
                                        navigation.navigate(
                                            'NewsDetailsScreen',
                                            item
                                        );
                                    } else if (selected.value == 'videos') {
                                        navigation.navigate(
                                            'YoutubeVideoDetailsScreen',
                                            item
                                        );
                                    } else if (
                                        selected.value == 'documentaries'
                                    ) {
                                        openBrowserAsync(item.link);
                                    } else if (selected.value == 'channels') {
                                        openBrowserAsync(item.link);
                                    }
                                }}
                            />
                        )}
                        ListFooterComponent={renderLoader}
                    />
                )}
                {errorMessage != '' && (
                    <AppText style={styles.results}>{errorMessage}</AppText>
                )}
            </View>
        </View>
    );
}

const styles = StyleSheet.create({
    loaderStyle: {
        marginVertical: 16,
        alignItems: 'center',
    },
    container: {
        padding: 15,
        paddingBottom: 50,
        // backgroundColor: colors.light,
        flexDirection: 'column',
        width: '100%',
    },
    innerContainer: {
        width: '100%',
    },
    button: {
        width: '100%',
        marginTop: 15,
        marginBottom: 15,
    },
    results: {
        marginTop: 15,
        paddingBottom: 50,
        textAlign: 'center',
    },
});

推荐答案

您需要使用useFocusEffect而不是useEffect:

  useFocusEffect(
    useCallback(() => {
      // Do something when the screen is focused

      return () => {
        // Do something when the screen is unfocused
        // Useful for cleanup functions
        setResultRecords([]);
        setInput('');
      };
    }, [])
  );

我建议您阅读文档https://reactnavigation.org/docs/navigation-lifecycle/

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