如何实现 Room LiveData 过滤器

Question

我不知道如何在 Repository 和 ViewModel 中正确实现过滤器查询，以使用它在 Textview 或其他任何东西中显示过滤后的字符串。我的Entity、Dao、Repository、ViewModel如下：

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)
    }
}

我将如何从这里开始以使其成为可能，例如在文本视图或类似内容中显示过滤后的用户字符串，以及如何在存储库和视图模型中正确编写方法？感谢您的帮助！

Answer 1

尝试以下方法

UserDao

更改getFilteredUser如下

    @Query("SELECT name FROM user_data WHERE name LIKE '%' || :filter || '%' LIMIT 1")
    fun getFilteredUser(filter: String): Stringl̥

UserRepo

使用协程执行数据库I/O操作

    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
            }
        }

如何实现 Room LiveData 过滤器

How to implement a Room LiveData filter

android

filter

kotlin

android-room

android-livedata