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Flashlight & Brightness Control Pattern

A sophisticated flashlight management system supporting granular brightness control, smooth fading effects, and hardware-aware protection.

1. Hardware Abstraction (FlashlightUtil)

Since flashlight intensity is an Android 13+ (SDK 33) feature, the utility provides a safe wrapper for both legacy toggling and modern strength adjustments.

Key Hardware APIs

  • turnOnTorchWithStrengthLevel(cameraId, level): Sets granular brightness.
  • FLASH_INFO_STRENGTH_MAXIMUM_LEVEL: Retrieves the maximum brightness step supported by the hardware (e.g., Pixel 7 supports 5-8 steps).

Smooth Fading Algorithm

To provide a premium feel, the flashlight doesn't just "snap" to a level. It uses a coroutine-based loop to step through intensity levels.

suspend fun fadeFlashlight(from: Int, to: Int, durationMs: Long = 250L) {
    val steps = 10
    for (i in 1..steps) {
        val level = from + ((to - from) * i / steps)
        cameraManager.turnOnTorchWithStrengthLevel(cameraId, level)
        delay(durationMs / steps)
    }
}

2. Business Logic (FlashlightHandler)

The handler manages the flashlight state within the app's core service (AccessibilityService).

Global Syncing

The system monitors onTorchModeChanged. If the flashlight is turned on externally (e.g., via the system Quick Settings tile), the app detects it and automatically fades the brightness up to the user's last saved intensity level.

Proximity Protection

The flashlight pulse (for notifications) is automatically suppressed if the proximity sensor is blocked (e.g., the phone is face-down on a desk or in a pocket) to save battery and prevent unnecessary light.

3. Live Control Notifications

When the flashlight is active, the app utilizes the Live Update Notification pattern to provide real-time feedback and control.

Key Features

  • Visual Progress: Uses Notification.ProgressStyle (Android 16+) to show a brightness bar.
  • Status Chips: Uses setShortCriticalText to display the percentage (e.g., "80%") in the status bar.
  • Priority: Uses setRequestPromotedOngoing to keep the controls at the top of the shade.

Quick Actions

  • Adjust: + and - buttons to step through brightness levels.
  • Kill Switch: A prominent "Off" button to immediately extinguish the light.

4. Flashlight Pulse (Notification Lighting)

A dedicated feature that pulses the flashlight when a notification arrives. It uses the fadeFlashlight utility to create a soft "breathing" light effect rather than a harsh strobe.

5. Implementation Tips

  • Camera Conflict: Always catch CameraAccessException with reason CAMERA_IN_USE. If the camera app is open, flashlight controls must be disabled or hidden.
  • Haptic Limits: Trigger a "Double Tap" haptic feedback when the user reaches the minimum (1) or maximum brightness level.
  • Default Levels: Use FLASH_INFO_STRENGTH_DEFAULT_LEVEL as the initial intensity if the user hasn't set a preference yet.