This article explains how to use Redis sorted sets (ZSET) together with user token or browser fingerprint identification to add, query, and clean online user entries, providing a simple yet effective method for counting active users in real time.
This article walks through implementing fingerprint login on Android, covering the legacy FingerprintManager API, the newer BiometricPrompt, integrating with Android Keystore for secure encryption, handling compatibility, UI considerations, and security best practices, complete with code examples and deployment results.
The article details Android 10’s fingerprint recognition architecture—four layers from application to driver—and explains the independent startup sequences of the framework and HAL, describing how the system repeatedly binds services, loads vendor modules, and establishes end‑to‑end data flow to the secure element.
Google’s fingerprint API, introduced in Android 6.0, can be integrated via the legacy FingerprintManager or the newer BiometricPrompt, using a wrapper that abstracts version differences, handling permissions, hardware checks, authentication callbacks, and optional reflection to retrieve fingerprint IDs and enrolled fingerprint lists for advanced login scenarios.
Developers can create a custom Android lock screen by starting a foreground service that registers a dynamic SCREEN_OFF broadcast, launching a lock‑screen activity with keyguard‑dismiss and immersive window flags, handling swipe‑to‑unlock gestures, making navigation bars transparent, and integrating fingerprint authentication while respecting system security constraints.
This article explains why a custom lock screen is useful, describes the core principles of implementing one on Android, and provides step‑by‑step code for broadcast registration, activity configuration, key event blocking, swipe‑to‑unlock logic, immersive and translucent UI flags, and fingerprint integration.
