Resolving ERR_PERMISSIONS_DENIED When Loading HTML Files in Android WebView

Описание: Discover the simple solution to the `ERR_PERMISSIONS_DENIED` error when loading HTML files from the Downloads folder in Android WebView. Learn how to ensure seamless access and file loading.
---
This video is based on the question https://stackoverflow.com/q/71876198/ asked by the user 'CaseyB' ( https://stackoverflow.com/u/236136/ ) and on the answer https://stackoverflow.com/a/71876460/ provided by the user 'CommonsWare' ( https://stackoverflow.com/u/115145/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Permission denied loading html from Downloads

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Resolving ERR_PERMISSIONS_DENIED When Loading HTML Files in Android WebView

When building an app that connects to a custom Bluetooth Low Energy (BLE) device, many developers face challenges with loading HTML files from the Downloads folder in an Android WebView. The problem arises when trying to display these HTML files, resulting in an ERR_PERMISSIONS_DENIED error. This guide will explore the underlying issue and provide a clear, structured solution to overcome this common hurdle.

Understanding the Problem

The crux of the problem lies in Android's file handling, especially from versions 10 and above. Android has introduced stricter permissions for accessing files in external storage, including the Downloads directory. When your app attempts to load HTML files that were copied to the Downloads folder via ADB (Android Debug Bridge), it may be met with a hostile response, leaving you puzzled as to why some files work while others don't.

Key Points:

Android file permissions have become stricter starting from version 10 and continuing into 11+ .

Android remembers which files your app has created and potentially denies access to files copied using methods like ADB.

Users often attempt to access HTML files placed in the Downloads folder directly, leading to permission issues.

Why the Issue Occurs

While your app may have the required permissions declared in the manifest (like READ_EXTERNAL_STORAGE and WRITE_EXTERNAL_STORAGE), there are nuanced rules at play.

Ownership & Permissions: Permissions are often tied to the app that created the file. When using ADB to place files in the Downloads folder, those files might lack the necessary privileges associated with your app.

Legacy External Storage: Using android:requestLegacyExternalStorage="true" aims to ease the transition but does not always guarantee functionality for external files not created by the app itself.

The Solution: Switch to getExternalFilesDir()

The most straightforward way to resolve the ERR_PERMISSIONS_DENIED is to stop relying on the Downloads folder altogether. Instead, you can utilize the app-specific directory available through the getExternalFilesDir(null) method in Android's Context. Here’s how to implement this solution:

Steps to Implement:

Use App-Specific File Directory:

Replace any code that currently references the Downloads folder with a call to getExternalFilesDir(null). This points to a directory where your app has full access, specifically:

[[See Video to Reveal this Text or Code Snippet]]

This ensures that all files created and stored are under your app's controls.

Transferring Files:

Instruct your UX team to transfer files directly to this directory instead of the Downloads folder. This can be done easily using a USB cable:

Connect the device to a desktop or notebook.

Drag and drop HTML files to Android/data/your.application.id/files/.

Load Files in WebView:

Ensure your WebView loads HTML content from the newly designated location rather than attempting to access the Downloads folder.

Benefits of This Approach:

More Control: You have complete control over file permissions since the files live within your app's protected storage area.

Simplicity: Your UX designers can still iterate quickly without dealing with complicated file transfer methods, fostering a more efficient workflow.

Compatibility: As Android continues to evolve, this approach is less likely to run into permission issues, aligning with best practices recommended by the Android developer community.

Conclusion

Moving to a more organized and permission-compliant directory structure is essential for developing applications that involve file management. By leveraging the functionalit