React Native 没有从 API 调用中获取最新数据

Question

I sicerely Apologies if this has been asked before. I am a bit new to react native and react in general.

my react nativee code is not fetcing the latest data see the code for the list component below I would deeply appreciate it if you can tell me why this is happening and how to make it pick the latest data

import React, { Component } from "react";
import {
  FlatList,
  Text,
  View,
  StyleSheet,
  ScrollView,
  ActivityIndicator
} from "react-native";
import Constants from "expo-constants";
import { createStackNavigator } from "@react-navigation/stack";
import { toCommaAmount } from "./utilities";

const Stack = createStackNavigator();

function MyStack() {
  return (
    <Stack.Navigator>
      <Stack.Screen name="Home" component={ExpenseList} />
      <Stack.Screen name="NewTransaction" component={ExpenseForm} />
    </Stack.Navigator>
  );
}

function Item({ title }) {
  return (
    <View style={styles.item}>
      <Text style={styles.title}>{title}</Text>
    </View>
  );
}

class ExpenseList extends Component {
  constructor(props) {
    super(props);
    this.state = {
      isLoading: true,
      dataSource: null
    };
  }

  componentDidMount() {
    return fetch("https://example.com/expense/api/get_all.php")
      .then(response => response.json())
      .then(responseJson => {
        this.setState({
          isLoading: false,
          dataSource: responseJson.items
        });
      })

      .catch(error => console.log(error));
  }

  render() {
    if (this.state.isLoading) {
      return (
        <View style={styles.container}>
          <ActivityIndicator />
        </View>
      );
    } else {
      let myExpenses = this.state.dataSource.map((val, key) => {
        return (
          <View key={key} style={styles.item}>
            <Text>
              {val.title} {toCommaAmount(val.amount)}
            </Text>
            <Text>{val.date_time}</Text>
          </View>
        );
      });

      return <View style={styles.container}>{myExpenses}</View>;
    }
  }
}

export default ExpenseList;

Answer 1

ComponentDidMount is a void function. I assume you have this problem because you try to return the result of the fetch execution.

Answer 2

Can you remove your api call out of componentDidMount(), because it gets invoked only once. Rename it to getRealData() and attach it to a button click. So every click on button will being up latest data from backend.