我在使用实时数据观察器观察3个不同的列表以在一个回收者视图中查看它们时遇到问题。这是场景：在ListsFragment中，我具有带有3个选项卡（WANT，PLAYING，PLAYED）和1个回收站视图的TabLayout。在不同的选项卡上，单击我从数据库加载不同的游戏列表，并在“回收者”视图中以“实时数据”观察者模式显示它们。在此之前，一切正常。当我按下一个游戏的“删除”按钮时，会发生问题，数据库已更新，但在回收站视图中加载的列表错误，而不是所选选项卡的列表（可能因为有3个活动的观察者），因此屏幕上的数据已更新游戏错误。
行为的Gif：https://gfycat.com/showyembarrassedbarasingha
[谁能帮我，我尝试了许多解决方案，但没有任何帮助，我被困了超过1个月。
这是代码。片段：
public class ListsFragment extends Fragment implements VisitedGameInterface {
public static final String TAG = ListsFragment.class.getSimpleName();
private static final int WANT = 0;
private static final int PLAYING = 1;
private static final int PLAYED = 2;
private int selectedTab = WANT;
private GameViewModel gameViewModel;
private GameVisitedAdapter gameAdapter;
private TextView noGamesTV;
public ListsFragment() {
// Required empty public constructor
}
public static ListsFragment newInstance(Bundle bundle) {
ListsFragment fragment = new ListsFragment();
fragment.setArguments(bundle);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_lists, container, false);
TabLayout listsTabLayout = view.findViewById(R.id.lists_tab_layout);
RecyclerView listsRecyclerView = view.findViewById(R.id.lists_recycler_view);
noGamesTV = view.findViewById(R.id.no_games_tv);
listsTabLayout.addTab(listsTabLayout.newTab().setText(getString(R.string.want)), true);
listsTabLayout.addTab(listsTabLayout.newTab().setText(getString(R.string.playing)));
listsTabLayout.addTab(listsTabLayout.newTab().setText(getString(R.string.played)));
listsTabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
listsRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity(), RecyclerView.VERTICAL, false));
listsRecyclerView.addItemDecoration(new DividerItemDecoration(getActivity(), DividerItemDecoration.VERTICAL));
gameAdapter = new GameVisitedAdapter(getActivity(), this);
listsRecyclerView.setAdapter(gameAdapter);
gameViewModel = ViewModelProviders.of(this).get(GameViewModel.class);
gameViewModel.getWantedGames().observe(this, new Observer<List<Game>>() {
@Override
public void onChanged(List<Game> wantedGames) {
if (wantedGames.size() != 0) {
noGamesTV.setVisibility(View.GONE);
}else {
noGamesTV.setText(R.string.no_wanted_games);
noGamesTV.setVisibility(View.VISIBLE);
}
gameAdapter.setGames(wantedGames);
gameAdapter.notifyDataSetChanged();
}
});
listsTabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
if (getActivity() != null && tab.getText() != null) {
if (tab.getText().equals("WANT")) {
selectedTab = tab.getPosition();
gameViewModel.getWantedGames().observe(getActivity(), new Observer<List<Game>>() {
@Override
public void onChanged(List<Game> wantedGames) {
if (wantedGames.size() != 0) {
noGamesTV.setVisibility(View.GONE);
} else {
noGamesTV.setText(R.string.no_wanted_games);
noGamesTV.setVisibility(View.VISIBLE);
}
gameAdapter.setGames(wantedGames);
gameAdapter.notifyDataSetChanged();
}
});
} else if (tab.getText().equals("PLAYING")) {
selectedTab = tab.getPosition();
gameViewModel.getPlayingGames().observe(getActivity(), new Observer<List<Game>>() {
@Override
public void onChanged(List<Game> playingGames) {
if (playingGames.size() != 0) {
noGamesTV.setVisibility(View.GONE);
} else {
noGamesTV.setText(R.string.no_playing_games);
noGamesTV.setVisibility(View.VISIBLE);
}
gameAdapter.setGames(playingGames);
gameAdapter.notifyDataSetChanged();
}
});
} else if (tab.getText().equals("PLAYED")){
selectedTab = tab.getPosition();
gameViewModel.getPlayedGames().observe(getActivity(), new Observer<List<Game>>() {
@Override
public void onChanged(List<Game> playedGames) {
if (playedGames.size() != 0) {
noGamesTV.setVisibility(View.GONE);
} else {
noGamesTV.setText(R.string.no_played_games);
noGamesTV.setVisibility(View.VISIBLE);
}
gameAdapter.setGames(playedGames);
gameAdapter.notifyDataSetChanged();
}
});
}
}
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
return view;
}
@Override
public void onGameDelete(final Game game) {
if (selectedTab == WANT){
game.setWanted(false);
showSnackBar(game, WANT);
} if (selectedTab == PLAYING){
game.setPlaying(false);
showSnackBar(game, PLAYING);
} if (selectedTab == PLAYED){
game.setPlayed(false);
showSnackBar(game, PLAYED);
}
gameViewModel.update(game);
gameAdapter.notifyDataSetChanged();
}
@Override
public void onVisitedGameClick(Game game) {
Intent intent = new Intent(getActivity(), GameActivity.class);
intent.putExtra("game", game);
startActivity(intent);
}
private void showSnackBar(final Game snackGame, final int selectedTab){
Snackbar snackbar = Snackbar.make(Objects.requireNonNull(getView()), snackGame.getName() + " deleted", Snackbar.LENGTH_LONG)
.setAction(R.string.undo, new View.OnClickListener() {
@Override
public void onClick(View view) {
if (selectedTab == WANT) snackGame.setWanted(true);
if (selectedTab == PLAYING) snackGame.setPlaying(true);
if (selectedTab == PLAYED) snackGame.setPlayed(true);
gameViewModel.insert(snackGame);
}
});
snackbar.show();
}
}
ListsFragment的XML
<RelativeLayout
android:id="@+id/lists_layout" xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical"
tools:context=".fragment.ListsFragment">
<com.google.android.material.tabs.TabLayout
android:id="@+id/lists_tab_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:tabSelectedTextColor="@color/button_blue"/>
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/lists_recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@id/lists_tab_layout"/>
<TextView
android:id="@+id/no_games_tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
tools:text="No games at this moment"
android:textColor="@color/text_black"
android:visibility="invisible"/>
</RelativeLayout>
适配器：
public class GameVisitedAdapter extends RecyclerView.Adapter<GameVisitedAdapter.GameVisitedViewHolder> {
private Context context;
private LayoutInflater inflater;
private List<Game> games = new ArrayList<>();
private VisitedGameInterface visitedGameInterface;
public GameVisitedAdapter(Context context, VisitedGameInterface visitedGameInterface){
this.context = context;
inflater = LayoutInflater.from(context);
this.visitedGameInterface = visitedGameInterface;
}
public void setGames(List<Game> games){
this.games = games;
}
@NonNull
@Override
public GameVisitedViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = inflater.inflate(R.layout.item_game_visited, parent, false);
return new GameVisitedViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull GameVisitedViewHolder holder, int position) {
Game game = games.get(position);
if (game.getCover() != null) {
Glide
.with(context)
.load(context.getString(R.string.cover_url) + game.getCover().getImage_id() + ".jpg")
.centerCrop()
.placeholder(context.getResources().getDrawable(R.drawable.placeholder))
.into(holder.gameCover);
}
holder.gameTitle.setText(game.getName());
SimpleDateFormat formatter = new SimpleDateFormat("dd MMM yyyy");
String dateString = formatter.format((new Date((long) game.getFirst_release_date() * 1000)));
holder.gameYear.setText(dateString);
}
@Override
public int getItemCount() {
return games.size();
}
class GameVisitedViewHolder extends RecyclerView.ViewHolder {
private ImageView gameCover, gameDeleteButton;
private TextView gameTitle, gameYear;
GameVisitedViewHolder(@NonNull View itemView) {
super(itemView);
gameCover = itemView.findViewById(R.id.game_cover);
gameTitle = itemView.findViewById(R.id.game_name);
gameYear = itemView.findViewById(R.id.game_release_year);
gameDeleteButton = itemView.findViewById(R.id.game_delete_button);
gameDeleteButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
visitedGameInterface.onGameDelete(games.get(getAdapterPosition()));
}
});
itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
visitedGameInterface.onVisitedGameClick(games.get(getAdapterPosition()));
}
});
}
}
}
ViewModel
public class GameViewModel extends AndroidViewModel {
private GameRepository gameRepository;
public GameViewModel(@NonNull Application application) {
super(application);
gameRepository = new GameRepository(application);
}
public void insert(Game game){
gameRepository.insert(game);
}
public void update(Game game){
gameRepository.update(game);
}
public void deleteGame(Game game){
gameRepository.delete(game);
}
public void deleteAll(){
gameRepository.deleteAll();
}
public void DeleteVisitedGames(){ gameRepository.deleteVisitedGames();}
public LiveData<List<Game>> getWantedGames(){
return gameRepository.getWantedGames();
}
public LiveData<List<Game>> getPlayingGames(){
return gameRepository.getPlayingGames();
}
public LiveData<List<Game>> getPlayedGames(){
return gameRepository.getPlayedGames();
}
public LiveData<List<Game>> getVisitedGames(){
return gameRepository.getVisitedGames();
}
public LiveData<List<Game>> getAllGamesFromDB(){
return gameRepository.getAllGamesFromDB();
}
}
存储库：
public class GameRepository {
private GameDao gameDao;
private LiveData<List<Game>> wantedGames;
private LiveData<List<Game>> playingGames;
private LiveData<List<Game>> playedGames;
private LiveData<List<Game>> visitedGames;
private LiveData<List<Game>> allGamesFromDB;
public GameRepository(Application application){
GameDatabase gameDatabase = GameDatabase.getInstance(application);
gameDao = gameDatabase.gameDao();
wantedGames = gameDao.getWantedGames();
playingGames = gameDao.getPlayingGames();
playedGames = gameDao.getPlayedGames();
visitedGames = gameDao.getVisitedGames();
allGamesFromDB = gameDao.getAllGamesFromDB();
}
public LiveData<List<Game>> getWantedGames(){
return wantedGames;
}
public LiveData<List<Game>> getPlayingGames(){
return playingGames;
}
public LiveData<List<Game>> getPlayedGames(){
return playedGames;
}
public LiveData<List<Game>> getVisitedGames(){
return visitedGames;
}
public LiveData<List<Game>> getAllGamesFromDB(){
return allGamesFromDB;
}
public void insert(Game game){
new InsertAsyncTask(gameDao).execute(game);
}
public void update(Game game){
new UpdateAsyncTask(gameDao).execute(game);
}
public void delete(Game game){
new DeleteItemAsyncTask(gameDao).execute(game);
}
public void deleteAll(){
new DeleteAllAsyncTask(gameDao).execute();
}
public void deleteVisitedGames() {new DeleteVisitedAsyncTask(gameDao).execute();}
//-------------INSERT GAME ASYNC TASK
private static class InsertAsyncTask extends AsyncTask<Game, Void, Void> {
private GameDao asyncDao;
public InsertAsyncTask(GameDao asyncDao){
this.asyncDao = asyncDao;
}
@Override
protected Void doInBackground(Game... games) {
asyncDao.insert(games[0]);
return null;
}
}
//-------------UPDATE GAME ASYNC TASK
private static class UpdateAsyncTask extends AsyncTask<Game, Void, Void> {
private GameDao asyncDao;
public UpdateAsyncTask(GameDao asyncDao){
this.asyncDao = asyncDao;
}
@Override
protected Void doInBackground(Game... games) {
asyncDao.updateGame(games[0]);
return null;
}
}
//----------DELETE GAME ASYNC TASK
private static class DeleteItemAsyncTask extends AsyncTask <Game, Void, Void> {
private GameDao asyncDao;
public DeleteItemAsyncTask(GameDao asyncDao){
this.asyncDao = asyncDao;
}
@Override
protected Void doInBackground(Game... games) {
asyncDao.deleteGame(games[0]);
return null;
}
}
//-------------DELETE ALL ASYNC TASK
private static class DeleteAllAsyncTask extends AsyncTask <Void, Void, Void>{
private GameDao asyncDao;
public DeleteAllAsyncTask(GameDao asyncDao){
this.asyncDao = asyncDao;
}
@Override
protected Void doInBackground(Void... voids) {
asyncDao.deleteAllGames();
return null;
}
}
//-------------DELETE VISITED GAMES ASYNC TASK
private static class DeleteVisitedAsyncTask extends AsyncTask <Void, Void, Void>{
private GameDao asyncDao;
public DeleteVisitedAsyncTask(GameDao asyncDao){
this.asyncDao = asyncDao;
}
@Override
protected Void doInBackground(Void... voids) {
asyncDao.deleteVisitedGames();
return null;
}
}
}
DAO：
@Dao
public interface GameDao {
@Insert(onConflict = OnConflictStrategy.REPLACE)
void insert(Game game);
@Delete
void deleteGame(Game game);
@Update
void updateGame(Game game);
@Query("DELETE FROM game_table")
void deleteAllGames();
@Query("SELECT * FROM game_table WHERE isWanted")
LiveData<List<Game>> getWantedGames();
@Query("SELECT * FROM game_table WHERE isPlaying")
LiveData<List<Game>> getPlayingGames();
@Query("SELECT * FROM game_table WHERE isPlayed")
LiveData<List<Game>> getPlayedGames();
@Query("SELECT * FROM game_table WHERE isVisited")
LiveData<List<Game>> getVisitedGames();
@Query("SELECT * FROM game_table")
LiveData<List<Game>> getAllGamesFromDB();
@Query("DELETE FROM game_table WHERE isVisited")
void deleteVisitedGames();
}
数据库：
@Database(entities = Game.class, version = 8, exportSchema = false)
@TypeConverters({Converters.class})
public abstract class GameDatabase extends RoomDatabase {
public abstract GameDao gameDao();
private static GameDatabase INSTANCE;
public static GameDatabase getInstance(Context context){
if (INSTANCE == null){
synchronized (GameDatabase.class){
if (INSTANCE == null){
INSTANCE = Room.databaseBuilder(context.getApplicationContext(),
GameDatabase.class, "game_database")
.fallbackToDestructiveMigration()
.addCallback(sRoomDatabaseCallback)
.build();
}
}
}
return INSTANCE;
}
private static RoomDatabase.Callback sRoomDatabaseCallback = new RoomDatabase.Callback(){
@Override
public void onOpen(@NonNull SupportSQLiteDatabase db) {
super.onOpen(db);
}
};
}
我的2cents：即使您更改了标签页，您的观察员仍然处于活动状态，因为您对所有内容使用同一张表，并且我相信（只需看一眼代码即可）您正在更新游戏条目（例如：isPlayed设置为false）因此它将更新发送给所有活动的观察者。
考虑到这一点，如果我在这里，您可以：
如果我不正确，选项2 e 3仍然可以解决您的问题。希望对您有所帮助！
p.s：您还可以在每次用户更改选项卡时都删除并插入观察者，但是我发现它不太简单。