Here is a sample solution: Query is : @Query(“SELECT * FROM user LIMIT :limit OFFSET :offset”) User[] loadAllUsersByPage(int limit,int offset); Here, it will list users based on limit and offset. if loadAllUsersByPage(2,0) it will return the first 2 rows from the table. if loadAllUsersByPage(2,1) it will return 2nd and 3rd rows from table. but if … Read more
You can’t pass parameters like that to room. It does not support a full expression language. You have to use primitive types to pass parameters. Like this, @Query(“SELECT * FROM ticket where user_id = :user_id”) LiveData<Ticket> loadFromUser(String user_id);
Kotlin isn’t preserving the names of the arguments properly – this is https://youtrack.jetbrains.com/issue/KT-17959 You can work around this by using :arg0, :arg1, etc, as parameter names in your @Query statements: @Query(“SELECT * FROM countries WHERE id = :arg0”) fun loadCountry(countryId: Int): LiveData<CountryEntity> @Query(“SELECT * FROM countries WHERE id = :arg0”) fun loadCountrySync(countryId: Int): CountryEntity
It’s because you are trying to modify the schema of the existing database without giving it any migration information. So basically it attempts to write the new database schema to the existing DB which doesn’t work. There are two ways around this. If you are in your development environment what you can do is fallback … Read more
Document is really confusing. Try with just below classes: 1) User Entity: @Entity public class User { @PrimaryKey public int id; // User id } 2) Pet Entity: @Entity public class Pet { @PrimaryKey public int id; // Pet id public int userId; // User id public String name; } 3) UserWithPets POJO: // Note: … Read more
UPD. last time I had this annoying issue Invalidate cache/Restart fixed this for me. Sigh Running the app in Debug mode (Win: Shift+F9 or Mac: Control+D) does the magic for me sometimes. Not sure if this is a bug or not. The android documentation doesn’t mention on this, so I guess it should just work … Read more
Use CASE Expression for SQLite to achieve this in Room DAO, @Query(“SELECT * FROM Persons ORDER BY CASE WHEN :isAsc = 1 THEN first_name END ASC, CASE WHEN :isAsc = 0 THEN first_name END DESC”) List<Person> getPersonsAlphabetically(boolean isAsc);
On the next line I am checking sections.getValue() which is always giving me null although I have data in the DataBase and later I am getting the value in the onChanged() method. This is normal behavior, because queries that return LiveData, are working asynchronously. The value is null at that moment. So calling this method … Read more
Do not use both suspend and Flow<> on the same method! Like this @Query(“SELECT * FROM user”) suspend fun loadAll(): Flow<Array<User>> Just @Query(“SELECT * FROM user”) suspend fun loadAll(): Array<User> OR @Query(“SELECT * FROM user”) fun loadAll(): Flow<Array<User>>
Go to folder Data/data/packageName/databases/ There has to be three files .db, .db-shm, .db-wal, copy all three files to one location and then open your Myapp.db these two extra files are needed to open db file