Yes, with the Android API, you cannot directly retrieve a previously initialized PowerManager.WakeLock by its tag after it has been released or is no longer in scope.

Why?

• PowerManager.WakeLock instances are managed by the system and are not stored or retrievable by tag once they are released or go out of scope.
• The PowerManager system service does not provide an API to look up or retrieve a WakeLock by its tag.

Workarounds

If you need to manage multiple WakeLock instances and refer to them later, you should track them yourself in your application code. For example:

1. Use a static map to track WakeLocks by tag

java
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public class WakeLockManager {
    private static final Map<String, PowerManager.WakeLock> wakeLockMap = new HashMap<>();

    public static PowerManager.WakeLock acquireWakeLock(Context context, String tag, int flags) {
        PowerManager powerManager = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
        PowerManager.WakeLock wakeLock = powerManager.newWakeLock(flags, tag);
        wakeLock.acquire();
        wakeLockMap.put(tag, wakeLock);
        return wakeLock;
    }

    public static PowerManager.WakeLock getWakeLock(String tag) {
        return wakeLockMap.get(tag);
    }

    public static void releaseWakeLock(String tag) {
        PowerManager.WakeLock wakeLock = wakeLockMap.get(tag);
        if (wakeLock != null && wakeLock.isHeld()) {
            wakeLock.release();
            wakeLockMap.remove(tag);
        }
    }
}

2. Always keep a reference to your WakeLock

Store the reference in a field or singleton, so you can release it later.

Key Points

• No system-level retrieval by tag: The Android API does not support this.
• Manual tracking is required: Use your own data structures (e.g., Map<String, WakeLock>) to manage and retrieve WakeLock instances.