如何等待检索到ViewModel的LiveData

public class MyViewModel extends ViewModel {
    private MutableLiveData<String> data;

    public LiveData<String> getData() {
        if (data == null) {
            data = new MutableLiveData<>();
        }
        return data;
    }

    public void fetchData() {
        // 从网络或数据库中获取数据
        // 将数据设置到LiveData中
        data.setValue("Hello, LiveData!");
    }
}

public class MyActivity extends AppCompatActivity {
    private MyViewModel viewModel;

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

        viewModel = ViewModelProviders.of(this).get(MyViewModel.class);

        viewModel.getData().observe(this, new Observer<String>() {
            @Override
            public void onChanged(String data) {
                // 当LiveData的值发生变化时，会回调该方法
                // 在这里更新UI或执行其他操作
                textView.setText(data);
            }
        });

        viewModel.fetchData();
    }
}