怎么知道Android手机会睡觉？

private BroadcastReceiver receiver = new BroadcastReceiver() {
public void onReceive(final Context context, final Intent intent) {

    /*
     * dispatch screen_off
         * to handler method
     */

    String iAction = intent.getAction();

    if (iAction.equals(Intent.ACTION_SCREEN_OFF))
    handleScreenAction(iAction);

}

};

static void registerReciever() {
    IntentFilter myFilter = new IntentFilter();
    // Catch screen off event
    myFilter.addAction(Intent.ACTION_SCREEN_OFF);
    registerReceiver(receiver, myFilter);
}