React Native Running on Expo - SQLite Error when using Pre-populated Database - TypeError: undefined is not a function (near '...db.transaction...')

Question

我在 Expo 上使用 React Native 和 SQlite 数据库，目标是创建一个离线 Android 应用程序。数据库已预先填充，因此我已将其复制到 assets/database/FarmersDB.db 文件夹。我已经阅读了官方文档以及提供的建议 here 和其他提供的解决方案，但最终出现以下错误。

TypeError: undefined is not a function (near '...db.transaction...')

我的代码如下：

//Login Component
import React, {useEffect, useState} from 'react'
import * as SQLite from 'expo-sqlite';
import * as FileSystem  from 'expo-file-system'
import {Asset } from 'expo-asset'

async function openDb() {
  if (!(await FileSystem.getInfoAsync(FileSystem.documentDirectory + "SQLite")).exists) {
    await FileSystem.makeDirectoryAsync(FileSystem.documentDirectory + "SQLite");
  }
  await FileSystem.downloadAsync(
    Asset.fromModule(require("../assets/database/FarmerDB.db")).uri,
    FileSystem.documentDirectory + "SQLite/FarmerDB.db"
  );
  return SQLite.openDatabase("FarmerDB.db","1.0");
}

const LoginScreen = () => {
  useEffect(() => {
    
    const db = openDb()
    db.transaction((tx) =>{
      tx.executeSql(
        "SELECT * FROM Farmer WHERE id = 1",
        [],
        (tx,results) =>{
          console.log("success")
        }
      )
    })
  }, []);
}

项目根目录下的metro.config.js文件如下

const { getDefaultConfig } = require('expo/metro-config');

const defaultConfig = getDefaultConfig(__dirname);

module.exports = {
    resolver: {
        assetExts: [...defaultConfig.resolver.assetExts,'db'],
    },
};

Answer 1

经过一番努力，我得到了解决方案，

const db = openDb() //This returns a promise

所以代码应该如下所示。

  const LoginScreen = () => {
  useEffect(() => {
   openDb()
    .then(db =>
    db.transaction((tx) =>{
      tx.executeSql(
        "SELECT * FROM Farmer WHERE id = 1",
        [],
        (tx,results) =>{
          console.log("success")
        })
    )
    })
  }, []);
}

React Native Running on Expo - SQLite Error when using Pre-populated Database - TypeError: undefined is not a function (near '...db.transaction...')

React Native Running on Expo - SQLite Error when using Pre-populated Database - TypeError: undefined is not a function (near '...db.transaction...')

sqlite

react-native

expo