Скачать или смотреть How to Properly Launch Your Android App on NFC Tag Scans Using TECH_DISCOVERED

Learn how to configure Android manifest and NFC tech filters to ensure your app is launched when an NFC tag is scanned instead of the system NFC service.
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This video is based on the question https://stackoverflow.com/q/79421565/ asked by the user 'Waza_Be' ( https://stackoverflow.com/u/327402/ ) and on the answer https://stackoverflow.com/a/79421586/ provided by the user 'Waza_Be' ( https://stackoverflow.com/u/327402/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

If you want your Android app to launch automatically when an NFC tag is scanned, simply requesting NFC permission and declaring intent filters might not be enough. By default, the Android system might intercept the NFC event and launch its own NFC service interface rather than your app.

This guide helps you configure your app manifest and NFC technology filters correctly to take control of NFC tag detection.



The Problem

You have declared the NFC permission and specified intent filters in your manifest to catch NFC tags, including:

Permissions and hardware requirements.

Intent filters for NDEF_DISCOVERED with HTTP/HTTPS schemes and custom MIME types.

A <meta-data> element referencing an XML tech list for TECH_DISCOVERED.

Yet, when scanning a tag (e.g., on a Pixel 8 device), your app is not launched. Instead, the system's NFC service UI appears.



Why Does This Happen?

The key is how tech lists are structured for TECH_DISCOVERED intent filters.

Your initial tech-list XML grouped all technologies within a single <tech-list> element. However, Android requires each technology or combination of technologies to be declared within its own separate <tech-list> element.

If multiple techs are grouped together inside one <tech-list>, Android treats this as one combined tech signature, which rarely matches the scanned tag, so your app does not get priority.



The Correct Solution: Separate <tech-list> Blocks

Separate each NFC tech in its own <tech-list> element. This way, your app can match any tag that supports any one of the technologies listed, allowing Android to identify your app as the handler.

Example:

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

Make sure your <meta-data> in the manifest points to this XML file.



Additional Tips

Continue to declare both NDEF_DISCOVERED and TECH_DISCOVERED intent filters in your activity as needed.

Define explicit MIME types or URI schemes in NDEF_DISCOVERED filters to catch specific tags.

Use the android.permission.NFC permission and hardware features to ensure only NFC-enabled devices install your app.

Test with actual NFC tags matching the tech types you declared.



Summary

When handling NFC tags in Android:

Declare NFC permissions and hardware features.

Use separate <tech-list> XML blocks for each NFC tech.

Link your manifest <meta-data> to this XML file.

This setup ensures your app catches NFC scans instead of the system NFC service, providing a seamless tag detection experience.