无法编辑或更新会议室数据库条目

Question

我正在构建一个应用程序，用户可以在其中存储他/她的用户名和密码。该应用程序具有简单的UI。主线程在操作栏上具有条目列表，FAB和“全部删除”图标。我的问题是我无法编辑和更新现有条目。

我的onCreate()的{​​{1}}中有以下代码。当用户按住一个条目时，它将启动MainActivity.java活动。这里发生的是，已启动的活动在其AddEditEntry.java字段中没有现有的条目数据：

EditText

在我的adapter.setOnItemLongClickListener(new RecyclerViewAdapter.OnItemLongClickListener() { @Override public void onItemLongClick(Entries entries) { Intent intent = new Intent(MainActivity.this, AddEditEntry.class); intent.putExtra(AddEditEntry.EXTRA_USERNAME, entry.getUsername()); intent.putExtra(AddEditEntry.EXTRA_HINT, entry.getHint()); intent.putExtra(AddEditEntry.EXTRA_PASSWORD, entry.getPassword()); intent.putExtra(AddEditEntry.EXTRA_ID, entry.getId()); startActivityForResult(intent, EDIT_ENTRY_REQUEST); } }); 活动中，保存按钮的AddEditEntry.java中包含以下代码。我将新数据添加为意图：

onClick

然后回到我的saveEntry.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent data = new Intent(); data.putExtra(EXTRA_USERNAME, usernameEditText.getText().toString()); data.putExtra(EXTRA_HINT, hintEditText.getText().toString()); data.putExtra(EXTRA_PASSWORD, passwordEditText.getText().toString()); int id = getIntent().getIntExtra(EXTRA_ID, -1); if(id != -1){data.putExtra(EXTRA_ID, id);} setResult(RESULT_OK, data); finish(); } }); ，这就是我的MainActivity.jav：

onActivityResult()

当我运行应用程序并尝试编辑条目时，Toast消息显示为“条目已更新！”。因此它可以运行该代码，但更改不存在。我尝试停止该应用程序并重新启动以刷新它，但它仍然不存在。

ViewModel.java：

@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    if(requestCode == ADD_ENTRY_REQUEST && resultCode == RESULT_OK){
        String username = Objects.requireNonNull(data).getStringExtra(AddEditEntry.EXTRA_USERNAME);
        String password = Objects.requireNonNull(data).getStringExtra(AddEditEntry.EXTRA_PASSWORD);
        String hint = Objects.requireNonNull(data).getStringExtra(AddEditEntry.EXTRA_HINT);

        Entries entry = new Entries(username, hint, password);
        viewModel.insert(entry);

        Toast.makeText(this, "Entry added!", Toast.LENGTH_SHORT).show();

    }else if(requestCode == EDIT_ENTRY_REQUEST && resultCode == RESULT_OK){
        int id = Objects.requireNonNull(data).getIntExtra(AddEditEntry.EXTRA_ID, -1);
        String username = Objects.requireNonNull(data).getStringExtra(AddEditEntry.EXTRA_USERNAME);
        String password = Objects.requireNonNull(data).getStringExtra(AddEditEntry.EXTRA_PASSWORD);
        String hint = Objects.requireNonNull(data).getStringExtra(AddEditEntry.EXTRA_HINT);

        if (id == -1){Toast.makeText(addEditEntry, "Something went wrong", Toast.LENGTH_SHORT).show();}

        Entries entry = new Entries(username, hint, password);
        entry.setId(id);
        viewModel.update(entry);

        Toast.makeText(this, "Entry updated", Toast.LENGTH_SHORT).show();

    }
    else{Toast.makeText(this, "Entry not added!", Toast.LENGTH_SHORT).show();}
}

EntryRepository.java：

public class EntryViewModel extends AndroidViewModel {
    private EntryRepository repository;
    private LiveData<List<Entries>> allEntries;


    public EntryViewModel(@NonNull Application application) {
        super(application);
        repository = new EntryRepository(application);
        allEntries = repository.getAllEntries();
    }

    public void insert(Entries entries){repository.insert(entries);}

    public void update(Entries entries){repository.update(entries);}

    public void delete(Entries entries){repository.delete(entries);}

    public void deleteAll(){repository.deleteAllEntries();}

    public LiveData<List<Entries>> getAllEntries() {return allEntries;}
}

EntryDAO.java：

public class EntryRepository {
    private EntryDAO entryDAO;
    private LiveData<List<Entries>> allEntries;

    public EntryRepository(Application application){
        EntryDatabase database = EntryDatabase.getInstance(application);
        entryDAO = database.generateDao();
        allEntries = entryDAO.getAllEntries();
    }

    public void insert(Entries entries){new InsertEntryAsyncTask(entryDAO).execute(entries);}

    public void update(Entries entries){new UpdateEntryAsyncTask(entryDAO).execute(entries);}

    public void delete(Entries entries){new DeleteEntryAsyncTask(entryDAO).execute(entries);}

    public void deleteAllEntries(){new DeleteAllEntriesAsyncTask(entryDAO).execute();}

    public LiveData<List<Entries>> getAllEntries(){return allEntries;}


    public static class InsertEntryAsyncTask extends AsyncTask<Entries, Void, Void>{
        private EntryDAO entryDAO;

        private InsertEntryAsyncTask(EntryDAO entryDAO){this.entryDAO = entryDAO;}

        @Override
        protected Void doInBackground(Entries... entries) {
            entryDAO.insert(entries[0]);
            return null;
        }
    }

    public static class UpdateEntryAsyncTask extends AsyncTask<Entries, Void, Void>{
        private EntryDAO entryDAO;

        private UpdateEntryAsyncTask(EntryDAO entryDAO){
            this.entryDAO = entryDAO;
        }
        @Override
        protected Void doInBackground(Entries... entries) {
            entryDAO.update(entries[0]);
            return null;
        }
    }

    public static class DeleteEntryAsyncTask extends AsyncTask<Entries, Void, Void>{
        private EntryDAO entryDAO;

        private DeleteEntryAsyncTask(EntryDAO entryDAO){this.entryDAO = entryDAO;}

        @Override
        protected Void doInBackground(Entries... entries) {
            entryDAO.delete(entries[0]);
            return null;
        }
    }

    public static class DeleteAllEntriesAsyncTask extends AsyncTask<Void, Void, Void>{
        private EntryDAO entryDAO;

        private DeleteAllEntriesAsyncTask(EntryDAO entryDAO){this.entryDAO = entryDAO;}

        @Override
        protected Void doInBackground(Void... voids) {
            entryDAO.deleteAllEntries();
            return null;
        }
    }
}

Entries.java：

@Dao
public interface EntryDAO {

    @Insert
    void insert(Entries entries);

    @Update
    void update(Entries entries);

    @Delete
    void delete(Entries entries);

    @Query("DELETE FROM entries_table")
    void deleteAllEntries();

    @Query("SELECT * FROM entries_table")
    LiveData<List<Entries>> getAllEntries();
}

这是我的@Entity(tableName = "entries_table") public class Entries { @PrimaryKey(autoGenerate = true) private int id; private String username, hint, password; public Entries(String username, String hint, String password){ this.username = username; this.hint = hint; this.password = password; } public Entries(){} public int getId() {return id;} public void setId(int id) {this.id = id;} public String getUsername() {return username;} public void setUsername(String username) {this.username = username;} public String getHint() {return hint;} public void setHint(String hint) {this.hint = hint;} public String getPassword() {return password;} public void setPassword(String password) {this.password = password;} } 类的onCreate()。我添加了以下Toast消息，以查看它是否完全在接收数据，结果却没有。 Toast消息为空：

AddEditEntry.java

Answer 1

这样做

在您的MainActivity.java

    ....
    ....
    adapter.setOnItemLongClickListener(new RecyclerViewAdapter.OnItemLongClickListener() {
        @Override
        public void onItemLongClick(Entries entries) {
            entry = entries;  // this is very important, entry holds the current edited item
            Intent intent = new Intent(MainActivity.this, AddEditEntry.class);
            intent.putExtra(AddEditEntry.EXTRA_USERNAME, entry.getUsername());
            intent.putExtra(AddEditEntry.EXTRA_HINT, entry.getHint());
            intent.putExtra(AddEditEntry.EXTRA_PASSWORD, entry.getPassword());
            // no need to pass the id, it's a autogenerated field 
            // intent.putExtra(AddEditEntry.EXTRA_ID, entry.getId());
            startActivityForResult(intent, EDIT_ENTRY_REQUEST);
        }
    });

    ....
    ...

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {

        if(requestCode == ADD_ENTRY_REQUEST && resultCode == RESULT_OK){
            ...
            ... 
        } else if(requestCode == EDIT_ENTRY_REQUEST && resultCode == RESULT_OK) {
            // in an Edit operation, id should not be modified, so, no need to pass this parameter 
            // int id = 
            // Objects.requireNonNull(data).getIntExtra(AddEditEntry.EXTRA_ID, -1);
            String username = Objects.requireNonNull(data).getStringExtra(AddEditEntry.EXTRA_USERNAME);
            String password = Objects.requireNonNull(data).getStringExtra(AddEditEntry.EXTRA_PASSWORD);
            String hint = Objects.requireNonNull(data).getStringExtra(AddEditEntry.EXTRA_HINT);

            // entry already exists, so, no need to create a new one            
            //Entries entry = new Entries(username, hint, password);
            //entry.setId(id);
            entry.setUsername(username);
            entry.setPassword(password);
            entry.setHint(hint);
            viewModel.update(entry);

            Toast.makeText(this, "Entry updated", Toast.LENGTH_SHORT).show();

        } else {
            Toast.makeText(this, "Entry not added!", Toast.LENGTH_SHORT).show();
        }
        super.onActivityResult(requestCode, resultCode, data);
    }

其他备注...

在您的RecyclerViewAdapter.java

    // This is not needed. Your list is already created in your Room query
    //private List<Entries> entries = new ArrayList<>();

    private List<Entries> entries;

在您的MainActivity.java

    // This is not needed
    // AddEditEntry addEditEntry;
    ....
    ....
    // addEditEntry = new AddEditEntry();