如何通过 Viewmodel 调用 sqlite 方法？

Question

我到处搜索，但没有找到任何关于使用 MVVM 的 sqlite 的信息或教程或博客。如何为我的 sqlite 方法创建视图模型？我尝试了各种方法来访问它，但给了我错误

以下是我的 sqlite 助手类代码

public class DbHelper extends SQLiteOpenHelper {

private static final int DATABASE_VERSION = 2;

static final String DATABASE_NAME = "kuncorosqlite.db";

public static final String TABLE_SQLite = "sqlite";

public static final String COLUMN_ID = "id";
public static final String COLUMN_NAME = "name";
public static final String COLUMN_ADDRESS = "address";

public DbHelper(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    final String SQL_CREATE_MOVIE_TABLE = "CREATE TABLE " + TABLE_SQLite + " (" +
            COLUMN_ID + " INTEGER PRIMARY KEY autoincrement, " +
            COLUMN_NAME + " TEXT NOT NULL, " +
            COLUMN_ADDRESS + " TEXT NOT NULL" +
            " )";

    db.execSQL(SQL_CREATE_MOVIE_TABLE);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_SQLite);
    onCreate(db);
}

public ArrayList<HashMap<String, String>> getAllData() {
    ArrayList<HashMap<String, String>> wordList;
    wordList = new ArrayList<HashMap<String, String>>();
    String selectQuery = "SELECT * FROM " + TABLE_SQLite;
    SQLiteDatabase database = this.getWritableDatabase();
    Cursor cursor = database.rawQuery(selectQuery, null);
    if (cursor.moveToFirst()) {
        do {
            HashMap<String, String> map = new HashMap<String, String>();
            map.put(COLUMN_ID, cursor.getString(0));
            map.put(COLUMN_NAME, cursor.getString(1));
            map.put(COLUMN_ADDRESS, cursor.getString(2));
            wordList.add(map);
        } while (cursor.moveToNext());
    }

    Log.e("select sqlite ", "" + wordList);

    database.close();
    return wordList;
}

public void insert(String name, String address) {
    SQLiteDatabase database = this.getWritableDatabase();
    String queryValues = "INSERT INTO " + TABLE_SQLite + " (name, address) " +
            "VALUES ('" + name + "', '" + address + "')";

    Log.e("insert sqlite ", "" + queryValues);
    database.execSQL(queryValues);
    database.close();
}

public void update(int id, String name, String address) {
    SQLiteDatabase database = this.getWritableDatabase();

    String updateQuery = "UPDATE " + TABLE_SQLite + " SET "
            + COLUMN_NAME + "='" + name + "', "
            + COLUMN_ADDRESS + "='" + address + "'"
            + " WHERE " + COLUMN_ID + "=" + "'" + id + "'";
    Log.e("update sqlite ", updateQuery);
    database.execSQL(updateQuery);
    database.close();
}

public void delete(int id) {
    SQLiteDatabase database = this.getWritableDatabase();

    String updateQuery = "DELETE FROM " + TABLE_SQLite + " WHERE " + COLUMN_ID + "=" + "'" + id + "'";
    Log.e("update sqlite ", updateQuery);
    database.execSQL(updateQuery);
    database.close();
}

} 到目前为止，我已经尝试过的视图模型：-

public class Viewmodell extends AndroidViewModel {

private DbHelper repository ;
 MutableLiveData<ArrayList<HashMap<String, String>>> allNotesLivedata;
public Viewmodell(@NonNull Application application) {
    super(application);
    repository = new DbHelper(application);
    allNotesLivedata = repository.getAllData();
}
void insert(String name,String Address) {
    repository.insert(name,Address);
}
void update(int id, String name, String address) {
    repository.update(id,name,address);
}
void delete(int id) {
    repository.delete(id);
}
public LiveData<ArrayList<HashMap<String, String>>> getAllNotes() {
    return allNotesLivedata;
}

}

请不要建议我使用room，因为这不是我的要求

Answer 1

错误只是表示您没有提交兼容的值：

在您的代码中，在创建 MutableLiveData 时，您已经分配了它

ArrayList<HashMap<String,String>>

但是在为 MutableLiveData 设置值时，您只是传递了一个 HashMap 。因此，您需要做的不是直接传递 HashMap，而是需要创建一个 ArrayList，然后向该 arrayList 传递您的 HashMap，然后将 ArrayList 设置为 MutableLiveData。

你可以这样做。下面的代码是为了说明目的

//Create an arrayList
ArrayList<HashMap> listofMaps = new ArrayList();
//then add all your hashmaps to your list
listofMaps.add(map);
//and then set it to the MutableLiveData
wordList.postValue(listOfMaps);

或者代替上面的过程，解决这个问题的第二种方法是，你只需要创建类型的MutableLiveData：HashMap

wordList = new MutableLiveData<HashMap<String,String>>();