Lock Screen

A minimal Android application (targeting Android 16 / API 36) that locks the device screen with a single tap on its launcher icon.

How it works

The app uses Android's Accessibility Services API.
When the service is enabled, tapping the app icon calls
AccessibilityService.GLOBAL_ACTION_LOCK_SCREEN — the screen locks instantly with no visible UI.

First-time setup

1. Install the APK.
2. Tap the Lock Screen icon.
3. A dialog will appear — tap Open Settings.
4. In Settings → Accessibility, find Lock Screen and toggle it on.
5. Return to the home screen. Tapping the icon now locks the screen immediately.

Requirements

Item	Value
Minimum Android version	Android 9 (API 28)
Target Android version	Android 16 (API 36)
Required setup	Enable the included Accessibility Service once

Why Accessibility?
Since Android 9 (API 28), only Device Policy / accessibility services can lock the screen programmatically. This app uses the least-privileged path: no device-admin enrollment, no additional permissions beyond BIND_ACCESSIBILITY_SERVICE (which is granted automatically to the declared service).

Building

Prerequisites

• Android Studio (Ladybug 2024.2 or newer) or Gradle 8.9 + JDK 17
• Android SDK platform 36

Build a debug APK

./gradlew assembleDebug

Build a release APK (minified)

./gradlew assembleRelease

The release APK will be in app/build/outputs/apk/release/.

Project structure

app/src/main/
├── AndroidManifest.xml                   – permissions & component declarations
├── java/com/lockscreen/app/
│   ├── LockActivity.kt                   – transparent launcher Activity
│   └── LockScreenService.kt              – AccessibilityService that locks the screen
└── res/
    ├── drawable/
    │   ├── ic_launcher_background.xml    – icon background (blue)
    │   └── ic_launcher_foreground.xml    – icon foreground (white padlock)
    ├── mipmap-anydpi-v26/
    │   └── ic_launcher.xml               – adaptive launcher icon
    ├── values/
    │   ├── strings.xml                   – all user-visible strings
    │   └── themes.xml                    – transparent Activity theme
    └── xml/
        └── accessibility_service_config.xml – service metadata

Privacy

The accessibility service sets android:accessibilityEventTypes="0", meaning it does not read, observe, or intercept any accessibility events on the device. It only performs a single global action (lock screen) when explicitly triggered by the launcher Activity.

License

MIT