问题
I do not know how to implement a filter query properly inside the Repository and the ViewModel to use it to display the filtered string in a Textview or anything else really. My Entity, Dao, Repository, and ViewModel are as follows:
User.kt
@Entity(tableName = "user_data")
data class User (
@PrimaryKey(autoGenerate = true) val id: Int,
@ColumnInfo(name = "name") val name: String
)
UserDao.kt
@Dao
interface UserDao {
@Insert
fun addUser(user: User)
@Query("SELECT name FROM user_data WHERE name LIKE :filter LIMIT 1")
fun getFilteredUser(filter: String): LiveData<String>
}
UserRepository.kt
class UserRepository(private val userDao: UserDao) {
fun addUser(user: User) { userDao.addUser(User) }
fun getFilteredUser(filter: String) {userDao.getFilteredUser(filter)}
}
UserViewModel.kt
class UserViewModel(application: Application): AndroidViewModel(application) {
private val repository: UserRepository
init {
val userDao = UserDatabase.getDatabase(application).userDao()
repository = UserRepository(userDao )
}
fun addUser(user: User) {
viewModelScope.launch(Dispatchers.IO){
repository.addUser(user)
}
}
fun getFilteredUser(filter: String){
return repository.getFilteredUser(filter)
}
}
How would I proceed from here to make it possible to e.g. display the filtered User String in a textview or anything like that and how do I write the method correctly inside the repository and the viewmodel? Thank you for your help!
回答1:
Try the following
UserDao
change getFilteredUser
as follows
@Query("SELECT name FROM user_data WHERE name LIKE '%' || :filter || '%' LIMIT 1")
fun getFilteredUser(filter: String): Stringl̥
UserRepo
use coroutines to perform the database I/O operations
suspend fun addUser(user: User) {
withContext(Dispatchers.IO) {
userDao.addUser(user)
}
}
suspend fun getFilteredUser(filter: String): String {
return withContext(Dispatchers.IO) {
userDao.getFilteredUser(filter)
}
}
ViewModel
fun addUser(user: User) {
viewModelScope.launch {
repository.addUser(user)
}
}
private val _dataToUi = MutableLiveData<String>()
val dataToUi: LiveData<String>
get() = _dataToUi
suspend fun getFilteredUser(filter: String): String? {
return withContext(Dispatchers.IO) {
repository.getFilteredUser(filter)
}
}
// to set the filterquery from the fragment/activity
fun setFliterQuery(query: String) {
viewModelScope.launch {
_dataToUi.value = getFilteredUser(query)
}
}
Activity
binding.button.setOnClickListener {
val queryKey = binding.queryKey.text.toString()
Log.i("activity", queryKey)
userViewModel.setFliterQuery(queryKey)
}
userViewModel.dataToUi.observe(this) { result ->
result?.apply {
Log.i("activity", result)
binding.resultText.text = result
}
}
来源:https://stackoverflow.com/questions/65634643/how-to-implement-a-room-livedata-filter