FileSystem copyAsync not working in iOS and Expo 50

ONLINECAST

3 min read

·

03-09-2024

10

0

Share

Conquering the "File '' is not readable" Error in Expo 50's FileSystem.copyAsync on iOS

You're not alone in encountering this frustrating "File '' is not readable" error when using FileSystem.copyAsync with Expo 50 on iOS. This issue stems from the fact that iOS's ph:// scheme, used for Photos library images, presents unique challenges for file handling.

Let's dissect the problem and explore solutions, drawing inspiration from helpful discussions on Stack Overflow.

Understanding the Problem:

The ph:// scheme identifies images within the iOS Photos library, which isn't a traditional file system. The FileSystem.copyAsync function is designed to work with files stored in a standard file system location. Trying to copy a ph:// URI directly results in the "File '' is not readable" error.

Solution: Leveraging the Asset API

The solution lies in utilizing the Asset API, provided by Expo, to access and handle photos from the iOS Photos library. This approach involves the following steps:

1. Acquire an Asset: Use the ImagePicker component from Expo to obtain an Asset object representing the selected photo. This Asset object contains information like URI, dimensions, and other useful details.
2. Convert to URI: Leverage the Asset.uri property, which provides a standard URI suitable for FileSystem.copyAsync.
3. Copy with FileSystem: Utilize FileSystem.copyAsync to copy the photo to your desired location.

Here's a code snippet demonstrating the process:

import * as ImagePicker from 'expo-image-picker';
import * as FileSystem from 'expo-file-system';

const handlePhotoSelection = async () => {
  try {
    // Use ImagePicker to get the Asset
    const result = await ImagePicker.launchImageLibraryAsync({
      mediaTypes: ImagePicker.MediaTypeOptions.Images,
    });

    if (result.cancelled) {
      console.log('Photo selection cancelled');
      return;
    }

    // Obtain the URI from the Asset object
    const uri = result.assets[0].uri;

    // Generate a unique filename for the copied image
    const time = new Date().getTime();
    const newUri = `${FileSystem.documentDirectory}/${time}.jpg`;

    // Copy the image using FileSystem.copyAsync
    await FileSystem.copyAsync({
      from: uri,
      to: newUri,
    });

    console.log('Image copied successfully!');

  } catch (error) {
    console.error('Error copying image:', error);
  }
};

Explanation:

• Import necessary components: We import ImagePicker for selecting images and FileSystem for file operations.
• handlePhotoSelection function: This function orchestrates the image selection and copy process.
• ImagePicker.launchImageLibraryAsync: We utilize the ImagePicker component to open the user's photo library and allow them to select an image. The mediaTypes parameter specifies we're seeking images.
• result.assets[0].uri: The uri property of the selected Asset object provides the correct URI for copying.
• FileSystem.copyAsync: We use this function to copy the image from the Asset URI to the desired location.
• FileSystem.documentDirectory: This constant provides a convenient path for storing files within the app's document directory.

Additional Tips:

• Permissions: Ensure you have the necessary permissions to access the iOS Photos library. Use the ImagePicker.requestMediaLibraryPermissionsAsync() function to request the permission dynamically if necessary.
• Error Handling: Implement robust error handling to gracefully manage situations like user cancellation, permission denials, and file copy failures.

References:

• Expo ImagePicker Documentation
• Expo FileSystem Documentation
• Stack Overflow Discussion: "Expo 45 ImagePicker URI not working with FileSystem.copyAsync"

By understanding the limitations of ph:// URIs and utilizing the Asset API to obtain a valid URI, you can successfully copy images from the iOS Photos library within your Expo 50 app.