protected void enqueue(Runnable runnable) {
        synchronized (LOCK) {
            checkRunning();
            this.handler.post(runnable);
        }
    }
Call from main thread or camera thread.

Enqueues a task on the camera thread.

@param runnable the task to enqueue
zxing-android-embedded/src/com/journeyapps/barcodescanner/camera/CameraThread.java