Caching Content in CapacitorJS Applications with the capacitor-cache-file Plugin

In modern mobile applications, it's common to require certain content to be available offline. A typical scenario is caching images so that users can view them even without an internet connection. In this article, we'll explore how to use the capacitor-cache-file plugin to cache files in CapacitorJS applications. We'll also demonstrate how to integrate it into a ReactJS project using a custom hook.

What is capacitor-cache-file?

capacitor-cache-file is a Capacitor plugin that enables caching of files of any type. It checks if a file is already cached and returns it if available; otherwise, it downloads the file, saves it to the cache, and returns the path to the saved file. The plugin also prevents duplication when the same URL is requested multiple times.

Installation

To install the plugin, run the following commands:

npm install capacitor-cache-file
npx cap sync

Plugin API

checkCache(...)

Checks if a file is present in the cache.

checkCache(options: { url: string; }) => Promise<{ base64: string | null; }>

• Parameters:
  • options: An object containing the url field—the URL of the file to check in the cache.
• Returns: A Promise that resolves to an object { base64: string | null; }.

downloadAndCache(...)

Downloads a file and saves it to the cache.

downloadAndCache(options: { url: string; }) => Promise<{ base64: string; }>

• Parameters:
  • options: An object containing the url field—the URL of the file to download and cache.
• Returns: A Promise that resolves to an object { base64: string; }.

Using the Plugin in ReactJS

To simplify the use of the plugin in a ReactJS application, you can create a custom hook useCache. This hook will handle the logic for checking the cache and downloading files.

Creating the useCache Hook

import { useEffect, useState } from "react";
import { cacheFile } from "capacitor-cache-file";

const useCache = (url: string, noCache?: boolean) => {
  const [cachedUrl, setCachedUrl] = useState<string | null>(null);

  useEffect(() => {
    if (noCache) {
      setCachedUrl(url);
      return;
    }
    if (url) {
      const fetchCache = async () => {
        const cacheCheck = await cacheFile.checkCache({ url });
        console.log("cacheCheck", cacheCheck);
        if (cacheCheck.base64) {
          setCachedUrl(cacheCheck.base64);
        } else {
          const cachedFile = await cacheFile.downloadAndCache({ url });
          setCachedUrl(cachedFile.base64);
        }
      };

      fetchCache();
    }
  }, [url]);

  return cachedUrl;
};

export { useCache };

In this hook:

• We use useState to store the cached URL.
• We use useEffect to monitor changes to the original URL.
• We check if the file is in the cache using checkCache.
• If the file is not in the cache, we download and cache it using downloadAndCache.
• We update the cachedUrl state after obtaining the data.

How to Use the useCache Hook

After creating the hook, you can use it in your components to display cached content.

import React from "react";
import { useCache } from "./useCache";

const CachedImage = ({ src, alt }) => {
  const cachedSrc = useCache(src);

  return <img src={cachedSrc || src} alt={alt} />;
};

export default CachedImage;

In this example:

• The CachedImage component accepts src and alt props.
• It uses the useCache hook to get the cached URL of the image.
• It displays the image using the cached URL or the original one if the cache is unavailable.

Using the capacitor-cache-file plugin makes it easy to add offline caching functionality to your CapacitorJS application. By creating a custom useCache hook, you can efficiently manage file caching and enhance the user experience by ensuring content is always accessible.

With this approach, you can expand your application's functionality by providing quick access to frequently used resources and reducing network load.

CapacitorJS CapacitorJS Offline Caching capacitor-cache-file ReactJS Mobile Development