碎片替换后回收器视图丢失

Question

我有一个单独的活动，它将包含回收器视图的片段替换为包含所选viewholder项目详细信息的片段。当按下后退按钮时，包含回收器视图的碎片将被恢复，但回收器视图项目将不再显示。但是，视图会在设备旋转时恢复。所有模型数据都存储在SQLite数据库中，适配器列表在其片段的恢复时更新。

CrimeListFragment.Java
public class CrimeListFragment extends Fragment {
private Callbacks callbacks;
public interface Callbacks {
public void onItemSelected(UUID id);
}
@Override
public void onAttach(@NonNull Context context) {
super.onAttach(context);
callbacks = (Callbacks) context;
}
@Override
public void onDetach() {
super.onDetach();
callbacks = null;
}
private RecyclerView crimeListRecycler;
private CrimeListAdapter adapter;
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
}
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_crime_list, container, false);
crimeListRecycler = view.findViewById(R.id.crime_list);
crimeListRecycler.setLayoutManager(new LinearLayoutManager(getActivity()));
updateUI();
return view;
}
@Override
public void onResume() {
super.onResume();
updateUI();
}
@Override
public void onCreateOptionsMenu(@NonNull Menu menu, @NonNull MenuInflater inflater) {
super.onCreateOptionsMenu(menu, inflater);
inflater.inflate(R.menu.fragment_crime_list, menu);
MenuItem showSubtitle = menu.findItem(R.id.show_subtitle);
}
@Override
public boolean onOptionsItemSelected(@NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.new_crime:
Crime crime = new Crime();
CrimeLab.get(getActivity()).addCrime(crime);
/*Intent intent = CrimeActivity.createIntent(getActivity(), crime.getId());
startActivity(intent);*/
callbacks.onItemSelected(crime.getId());
return true;
default:
return onOptionsItemSelected(item);
}
}
private void updateUI() {
List<Crime> crimes = CrimeLab.get(getActivity()).getCrimes();
if (adapter == null) {
adapter = new CrimeListAdapter(crimes);
crimeListRecycler.setAdapter(adapter);
} else {
adapter.setCrimesList(crimes);
adapter.notifyDataSetChanged();
}
}
public class CrimeListAdapter extends RecyclerView.Adapter<CrimeListAdapter.CrimeHolder> {
private List<Crime> crimeList;
public CrimeListAdapter(List<Crime> crimes) {
crimeList = crimes;
}
@NonNull
@Override
public CrimeHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(getActivity()).inflate(R.layout.list_item_crime, parent, false);
return new CrimeHolder(view);
}
@Override
public void onBindViewHolder(@NonNull CrimeHolder holder, int position) {
Crime crime = crimeList.get(position);
holder.bind(crime);
}
@Override
public int getItemCount() {
return crimeList.size();
}
public void setCrimesList(List<Crime> crimes) {
crimeList = crimes;
}
public class CrimeHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
private Crime crime;
private TextView crimeTitleTextView;
private TextView crimeDateTextView;
public CrimeHolder(@NonNull View itemView) {
super(itemView);
crimeTitleTextView = itemView.findViewById(R.id.crime_title);
crimeDateTextView = itemView.findViewById(R.id.crime_date);
itemView.setOnClickListener(this);
}
public void bind(Crime crime) {
this.crime = crime;
crimeTitleTextView.setText(crime.getTitle());
crimeDateTextView.setText(crime.getDate().toString());
}
@Override
public void onClick(View v) {
callbacks.onItemSelected(crime.getId());
/*Intent intent = CrimeActivity.createIntent(getActivity(), crime.getId());
startActivity(intent);*/
}
}
}
}
MasterActivity
public class MasterActivity extends AppCompatActivity implements CrimeListFragment.Callbacks {

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fragment);
FragmentManager fm = getSupportFragmentManager();
Fragment fragment = fm.findFragmentById(R.id.fragment_container);
if (fragment == null) {
fragment = new CrimeListFragment();
fm.beginTransaction()
.add(R.id.fragment_container, fragment)
.commit();
}
}
@Override
public void onItemSelected(UUID id) {
Fragment fragment = CrimeFragment.newInstance(id);
FragmentManager fm = getSupportFragmentManager();
fm.beginTransaction()
.replace(R.id.fragment_container, fragment)
.addToBackStack(null)
.commit();
}
}

Answer 1

请分享您的代码。当你在可回收的新碎片上更换/添加碎片时需要检查的东西。