要将LiveData作为Service观察者，可以按照以下步骤进行操作：

步骤1：创建一个Service类，该类继承自Service，并在其中定义一个Binder内部类。这个Binder类将用于将Service和Activity进行通信。

public class MyService extends Service {
    private final IBinder binder = new MyBinder();
    private MutableLiveData data = new MutableLiveData<>();

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return binder;
    }

    public void updateData(String newData) {
        data.setValue(newData);
    }

    public LiveData getData() {
        return data;
    }

    public class MyBinder extends Binder {
        public MyService getService() {
            return MyService.this;
        }
    }
}

步骤2：在Activity中绑定Service，并将LiveData作为观察者进行观察。

public class MainActivity extends AppCompatActivity {
    private MyService myService;
    private boolean isBound = false;

    private TextView textView;

    private ServiceConnection serviceConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
            MyService.MyBinder binder = (MyService.MyBinder) iBinder;
            myService = binder.getService();
            myService.getData().observe(MainActivity.this, new Observer() {
                @Override
                public void onChanged(String newData) {
                    textView.setText(newData);
                }
            });
        }

        @Override
        public void onServiceDisconnected(ComponentName componentName) {
            myService = null;
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        textView = findViewById(R.id.textView);
    }

    @Override
    protected void onStart() {
        super.onStart();
        Intent intent = new Intent(this, MyService.class);
        bindService(intent, serviceConnection, Context.BIND_AUTO_CREATE);
        isBound = true;
    }

    @Override
    protected void onStop() {
        super.onStop();
        if (isBound) {
            unbindService(serviceConnection);
            isBound = false;
        }
    }
}

通过以上代码，我们创建了一个MyService类作为Service，并在其中定义了一个LiveData对象data。我们还定义了一个updateData方法用于更新LiveData的值。在MainActivity中，我们通过bindService方法绑定了MyService，并在onServiceConnected方法中将LiveData作为观察者进行观察。当LiveData的值发生变化时，Observer将更新TextView的显示。