Android - LiveData没有更新

public class MyViewModel extends ViewModel {
    private MutableLiveData<String> liveData = new MutableLiveData<>();

    public LiveData<String> getLiveData() {
        return liveData;
    }

    public void updateData(String newData) {
        liveData.setValue(newData); // 在主线程中使用 setValue
        // 或者在后台线程中使用 postValue
        // liveData.postValue(newData);
    }
}

public class MyActivity extends AppCompatActivity {
    private MyViewModel viewModel;

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

        viewModel = new ViewModelProvider(this).get(MyViewModel.class);

        viewModel.getLiveData().observe(this, new Observer<String>() {
            @Override
            public void onChanged(String newData) {
                // 更新 UI
                textView.setText(newData);
            }
        });
    }

    // 在某个事件中更新 LiveData
    public void onUpdateButtonClicked(View view) {
        viewModel.updateData("New Data");
    }
}