问题描述
我正在编写一个简单的应用程序，该应用程序使用 Room 在数据库中存储2个字符串值（我正在尝试学习该库）。因此，我的名单上只有一行。首次提出。其余的不显示。这种行为的原因是什么？
型号
@Entity
public class Note {
@PrimaryKey(autoGenerate = true)
private long id;
private String title;
private String text;
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
}
}
NoteDao
@Dao
public interface NoteDao {
@Insert
void insert(Note note);
@Delete
void delete(Note note);
@Query("SELECT * FROM Note")
List<Note> getAllNotes();
}
AppDatabase
@Database(entities = Note.class,version = 1)
public abstract class AppDatabase extends RoomDatabase {
public abstract NoteDao getNoteDao();
}
DataManager
public class DataManager {
private AppDatabase appDatabase;
public DataManager (AppDatabase appDatabase) {
this.appDatabase = appDatabase;
}
public List <Note> getNotes () {
try {
return new GetNotes (). execute (). get ();
} catch (ExecutionException | InterruptedException e) {
e.printstacktrace ();
return null;
}
}
public void insertNote (Note note) {
new InsertNote (note) .execute ();
}
public void deleteNote (Note note) {
new DeleteNote (note) .execute ();
}
// Get all notes
public class GetNotes extends AsyncTask <Void,Void,List <Note>> {
@Override
protected List <Note> doInBackground (Void ... voids) {
return appDatabase.getNoteDao (). getAllNotes ();
}
}
// Insert note
public class InsertNote extends AsyncTask <Void,Void> {
private Note note;
InsertNote (Note note) {
this.note = note;
}
@Override
protected Void doInBackground (Void ... voids) {
appDatabase.getNoteDao (). insert (note);
return null;
}
}
// Delete note
public class DeleteNote extends AsyncTask <Void,Void> {
private Note note;
public DeleteNote (Note note) {
this.note = note;
}
@Override
protected Void doInBackground (Void ... voids) {
appDatabase.getNoteDao (). delete (note);
return null;
}
}
}
Mvp
public interface NoteListView extends MvpView {
void showNoteList(List<Note> note);
}
演示者
public class NoteListPresenter extends MvpPresenter<NoteListView> {
private DataManager dataManager;
public NoteListPresenter(DataManager dataManager) {
this.dataManager = dataManager;
}
public void getNotes(){
getView().showNoteList(dataManager.getNotes());
}
public void deleteNote(Note note) {
dataManager.deleteNote(note);
getView().showNoteList(dataManager.getNotes());
}
}
适配器
public class NoteAdapter extends RecyclerView.Adapter<NoteAdapter.ViewHolder> {
private List<Note> listNote;
private Context context;
public NoteAdapter(Context context,List<Note> listNote) {
this.listNote = listNote;
this.context = context;
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent,int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_list,parent,false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull ViewHolder holder,int position) {
holder.title.setText(listNote.get(position).getTitle());
holder.text.setText(listNote.get(position).getText());
}
@Override
public int getItemCount() {
return listNote.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
TextView title,text;
public ViewHolder(@NonNull View itemView) {
super(itemView);
title = itemView.findViewById(R.id.title);
text = itemView.findViewById(R.id.text);
}
}
}
MainActivity
public class MainActivity extends AppCompatActivity implements NoteListView {
private NoteListPresenter presenter;
private RecyclerView recyclerView;
private NoteAdapter noteAdapter;
private ConstraintLayout constraintLayout;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
constraintLayout = findViewById(R.id.coordinatorMain);
recyclerView = findViewById(R.id.recycler);
recyclerView.setLayoutManager(new @R_502_609@(this,@R_502[email protected],false));
presenter = new NoteListPresenter(App.getDataManager());
presenter.attachView(this);
presenter.getNotes();
}
public void onNextActivity(View view){
startActivity(new Intent(MainActivity.this,AddNoteActivity.class));
}
@Override
public void showNoteList(List<Note> note) {
noteAdapter = new NoteAdapter(this,note);
recyclerView.setAdapter(noteAdapter);
}
@Override
protected void onResume() {
super.onResume();
presenter.getNotes();
}
@Override
public void showMessage(String message) {
Snackbar.make(constraintLayout,message,Snackbar.LENGTH_SHORT).show();
}
}
UPD
SaveNoteView
public interface SaveNoteView extends MvpView {
void insertNote(Note note);
}
SaveNotePresenter
public class SaveNotePresenter extends MvpPresenter<SaveNoteView> {
private DataManager dataManager;
public SaveNotePresenter(DataManager dataManager) {
this.dataManager = dataManager;
}
public void insertNote(Note note){
dataManager.insertNote(note);
getView().insertNote(note);
}
}
AddNoteActivity
public class AddNoteActivity extends AppCompatActivity implements SaveNoteView {
private TextInputEditText title,text;
private ConstraintLayout constraintLayout;
private SaveNotePresenter presenter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add_note);
constraintLayout = findViewById(R.id.constrainAdd);
title = findViewById(R.id.titleEditText);
text = findViewById(R.id.textEditText);
presenter = new SaveNotePresenter(App.getDataManager());
presenter.attachView(this);
}
//Save a note
public void saveNote(View view){
Note note = new Note();
note.setTitle(title.getText().toString());
note.setText(text.getText().toString());
presenter.insertNote(note);
finish();
}
@Override
public void insertNote(Note note) {
DataManager dataManager = App.getDataManager();
dataManager.insertNote(note);
}
@Override
public void showMessage(String message) {
Snackbar.make(constraintLayout,Snackbar.LENGTH_SHORT).show();
}
}
解决方法
很可能在整个过程中只有1个ID被蜜蜂替换（如果不是这种情况，请检查插入频率）
我将Kotlin与Room一起使用，但是在this official example中，他们有一个公共的自动生成的primaryKey，Room可能需要它来访问它并自动生成它。因此，将变量设为public，看看它是否有效
,没有问题。我只是在全屏模式下为 item_list 指定了父级布局。因此，后续的不可见。愚蠢的错误：D