如何在 React native (expo) 中创建文本文件？

Question

这是我正在尝试的功能。

saveFile = () => {
    let filename = Expo.FileSystem.documentDirectory + "text.txt";
    Expo.FileSystem.writeAsStringAsync(filename, "Hello World");
}

loadFile = () => {
    let filename = Expo.FileSystem.documentDirectory + "text.txt";
    let str = Expo.FileSystem.readAsStringAsync(filename, "Hello World");
    //alert(str);
}

警告：

[Unhandled promise rejection: Error: Argument of an incompatible class: class java.lang.String cannot be passed as an argument to parameter expecting interface java.util.Map.]

但是有一个警告，有人知道怎么做吗？

-------------更新：console.log 输出-------------

[15:27:36] Promise {
[15:27:36]   "_40": 0,
[15:27:36]   "_55": null,
[15:27:36]   "_65": 0,
[15:27:36]   "_72": null,
[15:27:36] }

------------------update: 代码更新---------------

saveFile = async () => {
    let filename = Expo.FileSystem.documentDirectory + "text.txt";
    await FileSystem.writeAsStringAsync(filename, "Hello World", { encoding: FileSystem.EncodingTypes.UTF8 });
}

loadFile = async () => {
    let filename = Expo.FileSystem.documentDirectory + "text.txt";
    file = await FileSystem.readAsStringAsync(filename, { encoding: FileSystem.EncodingTypes.UTF8 });
    return file;
}

getTextFromFile = () => {
    value = this.loadFile();
    alert(value);
    console.log(value);
}

hello world 似乎没有写入文件
------------更新-------------
我添加了一行，text.txt文件出现在我的android模拟器中的Document/DCIM/text.txt，但是必须使用“MediaLibrary.createAssetAsync”，如果是，如何控制文件夹名称？

await MediaLibrary.createAssetAsync(`${FileSystem.documentDirectory}text.txt`);

Answer 1

我已经修改了问题中的代码，并最终设法完成了这项工作。此函数在 Downloads 文件夹中创建 .txt 文件：

import * as MediaLibrary from 'expo-media-library';
import * as FileSystem from 'expo-file-system';
import * as Permissions from 'expo-permissions';

saveFile = async () => {
    const { status } = await Permissions.askAsync(Permissions.CAMERA_ROLL);
    if (status === "granted") {
        let fileUri = FileSystem.documentDirectory + "text.txt";
        await FileSystem.writeAsStringAsync(fileUri, "Hello World", { encoding: FileSystem.EncodingType.UTF8 });
        const asset = await MediaLibrary.createAssetAsync(fileUri)
        await MediaLibrary.createAlbumAsync("Download", asset, false)
    }
}