如何避免“过多的挂起回调:501"在 React Native 中下载图像时出错? [英] How to avoid "Excessive number of pending callbacks: 501" error during images download in React Native?

问题描述

我需要在按下按钮时下载一组图像.目前，我正在使用 react-native-fs 这样做:

I need to download a collection of images on button press. Currently, I'm doing it this way using react-native-fs:

const downloadImageItem = async (imgUrl, id) => {
  const path = `${RNFS.DocumentDirectoryPath}/${id}.jpg`;

  RNFS.downloadFile({
    fromUrl: imgUrl,
    toFile: path,
  });
};

const downloadImages = async (items) => {
  for (const item of items) {
    if (item.images.length) {
      await downloadImageItem(item.images[0].thumb, item.images[0].id);
    }
  }
  return Promise.resolve();
};

从我的减速器中为 3 种类型的项目调用函数:

Calling the function from my reducer for 3 types of items:

await downloadImages(items_one);
await downloadImages(items_two);
await downloadImages(items_three);

我的问题是有时我会收到一条错误消息，内容为:待处理的回调数量过多:501

My issue is that sometimes I receive an error message that says: Excessive number of pending callbacks: 501

有没有更好的方法来做同样的事情，这样错误就不会出现?

Is there a better way of doing the same thing, so that the error does not appear?

推荐答案

一个类似的issue 于 2019 年 12 月在 react-native 存储库中打开，它仍然没有关闭或解决，但我想你可能会发现这个 评论 很有用.

A similar issue was opened on the react-native repository in December 2019, it still hasn't been closed or addressed but I think you may find this comment useful.

那里描述的问题是排队太多 Promise 调用可能会出现问题.评论者建议使用名为 Promise.map() 的 Promise 实用程序函数，该函数具有开箱即用的并发控制，来自 bluebird 库.

The problem being described there is that queueing too many Promise calls can be problematic. The commenter suggested using a Promise utility function called Promise.map() which has concurrency control out of the box, from the bluebird library.

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