/** Enqueue a message to this state machine. */
  public final void sendMessage(Message msg) {
    // mSmHandler can be null if the state machine has quit.
    if (mSmHandler == null) return;

    mSmHandler.sendMessage(msg);
  }
  /** Enqueue a message to this state machine. */
  public final void sendMessage(int what, Object obj) {
    // mSmHandler can be null if the state machine has quit.
    if (mSmHandler == null) return;

    mSmHandler.sendMessage(obtainMessage(what, obj));
  }