如何实现Room LiveData过滤器 [英] How to implement a Room LiveData filter

问题描述

我不知道如何在存储库和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.我的实体，Dao，存储库和ViewModel如下:

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)
    }
}

我将如何从此处进行操作，例如在textview或类似的视图中显示过滤的用户字符串，如何在存储库和viewmodel中正确编写该方法? 谢谢您的帮助！

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!

推荐答案

尝试以下操作

UserDao

如下更改getFilteredUser

    @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

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)
        }
    }

活动

        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
            }
        }

这篇关于如何实现Room LiveData过滤器的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！