Android: Keep camera-LED on after screen turns off

Question

since i'm at the beginning with Android coding i hesitated to post my question, but now i'm at the point where i can't resist.

I have a service which turns on the camera-LED onCreate:

@Override
public void onCreate() {
// make sure we don't sleep
this.pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
this.mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "SleepLED");

    this.mTimer = new Timer();
    this.mTimerTask = new TimerTask() {
        public void run() {
        // turn on the LED
        setFlashlight(Camera.Parameters.FLASH_MODE_TORCH);

        mWakeLock.acquire();
        }
    };

    // Get the notification-service
    this.mNM = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);
    // Display a notification about us starting.  We put an icon in the status bar.
    showNotification();

    // Open camera
    this.frontCam = Camera.open();
    this.frontCamPara = frontCam.getParameters();
    this.frontCam.lock();


    // Schedule the TimerTask
    this.mTimer.schedule(mTimerTask, 0);
}

I can tell that the WakeLock acquires, I tested with FULL_WAKE_LOCK and it didn't turn off considering Screen Time-Out. But since the Screen isn't need to be on I don't want to use the full wakelock.

The Cyanogenmod for my phone (HTC Legend) brings an torch-app which can do what i want. Its source code is here:
https://github.com/CyanogenMod/android_packages_apps_Torch/tree/gingerbread/src/net/cactii/flash2
I noticed that the light turns off for a short moment with that app, if this is a hint for someone, obviously not for me ;(

I don't expect someone to change my code to do what i want but I'd be thankful if anyone could point me in the right direction!

Greets
SJ

Answer 1

I have found a solution to the problem. When the phone turns off the screen it does deactivate the camera LED, but it allows a user to reactivate it like this:

@Override
public void onCreate() {
    // assume we start with screen on and save that state ;-)
    this.pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
    screenOn = this.pm.isScreenOn();

    // program a timer which checks if the light needs to be re-activated
    this.mTimer = new Timer();
    this.mTimerTask = new TimerTask() {
        public void run() {
            // re-activate the LED if screen turned off
            if(!pm.isScreenOn() && pm.isScreenOn() != screenOn) {
                Log.i("SleepLEDservice", "re-activated the LED");

                // really it's NOT ENOUGH to just "turn it on", i double-checked this
                setFlashlight(Camera.Parameters.FLASH_MODE_OFF);
                setFlashlight(Camera.Parameters.FLASH_MODE_TORCH);
            }
            screenOn = pm.isScreenOn();                 
        }
    };
}

private void setFlashlight(String newMode) {
    try {
        this.frontCamPara = this.frontCam.getParameters();
        if(this.frontCamPara.getFlashMode() != newMode) {
            this.frontCamPara.setFlashMode(newMode);
            this.frontCam.setParameters(frontCamPara);  
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}

The key is changing the state back to FLASH_MODE_OFF and than back to FLASH_MODE_TORCH.