按back箭头按钮从DetailFragment back to ThumbnailFragment后，显示的下拉菜单的AutoCompleteTextView选项消失

@Override
public void onSaveInstanceState(@NonNull Bundle outState) {
    super.onSaveInstanceState(outState);
    // 保存AutoCompleteTextView的状态
    outState.putString("autoCompleteText", autoCompleteTextView.getText().toString());
}

@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    if (savedInstanceState != null) {
        // 恢复AutoCompleteTextView的状态
        autoCompleteTextView.setText(savedInstanceState.getString("autoCompleteText"));
    }
    // 设置数据源
    setupAutoCompleteTextView();
}

private void setupAutoCompleteTextView() {
    // 假设您有一个数据源列表
    List<String> suggestions = getSuggestions();
    ArrayAdapter<String> adapter = new ArrayAdapter<>(requireContext(),
            android.R.layout.simple_dropdown_item_1line, suggestions);
    autoCompleteTextView.setAdapter(adapter);
}

public class ThumbnailViewModel extends ViewModel {
    private final MutableLiveData<List<String>> suggestions = new MutableLiveData<>();

    public LiveData<List<String>> getSuggestions() {
        return suggestions;
    }

    public void loadSuggestions() {
        // 加载建议项
        List<String> suggestionList = fetchSuggestions();
        suggestions.setValue(suggestionList);
    }

    private List<String> fetchSuggestions() {
        // 实现获取建议项的逻辑
        return new ArrayList<>();
    }
}

public class ThumbnailFragment extends Fragment {
    private ThumbnailViewModel viewModel;
    private AutoCompleteTextView autoCompleteTextView;

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        autoCompleteTextView = view.findViewById(R.id.autoCompleteTextView);
        viewModel = new ViewModelProvider(this).get(ThumbnailViewModel.class);

        viewModel.getSuggestions().observe(getViewLifecycleOwner(), suggestions -> {
            ArrayAdapter<String> adapter = new ArrayAdapter<>(requireContext(),
                    android.R.layout.simple_dropdown_item_1line, suggestions);
            autoCompleteTextView.setAdapter(adapter);
        });

        viewModel.loadSuggestions();
    }
}