将房间数据库值与用户输入进行比较

Question

如何将房间数据库中的值与文本字段进行比较？我想将用户输入值与凭据视图模型进行比较，但我不知道该怎么做。我已经在 credentialDao 中设置了查询，因此获取的值应该在视图模型中。但我无法比较它。 凭证道

@Dao
interface CredentialDao {
    //if user name same ignore
    @Insert(onConflict = OnConflictStrategy.IGNORE)
    suspend fun addUser(credential: Credential)

    @Update
    suspend fun updateUser(credential: Credential)

    @Query("SELECT * FROM credential_table WHERE userName LIKE :userName AND password LIKE :password")
    fun readAllData(userName: String, password: String): Credential
}

凭证数据库

@Database(entities = [Credential::class], version = 1, exportSchema = false)
@TypeConverters(dateConverter::class)
abstract class CredentialDatabase: RoomDatabase() {

    abstract fun credentialDao(): CredentialDao

    companion object{
        @Volatile
        private var INSTANCE: CredentialDatabase? = null
        val migration_1_2: Migration = object: Migration(2,1){
            override fun migrate(database: SupportSQLiteDatabase){

            }
        }

        fun getDatabase(context: Context): CredentialDatabase{
            val tempInstance = INSTANCE
            if(tempInstance != null){
                return tempInstance
            }
            synchronized(this){
                val instance = Room.databaseBuilder(
                    context.applicationContext,
                    CredentialDatabase::class.java,
                    "credential_database"
                ).fallbackToDestructiveMigration()
                    .build()
                INSTANCE = instance
                return instance
            }
        }
    }

}

凭据存储库

class CredentialRepository(private val credentialDao: CredentialDao) {


    suspend fun addCredential(credential: Credential){
        credentialDao.addUser(credential)
    }
    suspend fun updateCredential(credential: Credential){
        credentialDao.updateUser(credential)
    }
    fun readAllData(username: String,password:String) {
        credentialDao.readAllData(username,password)
    }
}

凭据视图模型

class CredentialViewModel(application: Application): AndroidViewModel(application) {
    private val repository: CredentialRepository

    init{
        val credentialDao = CredentialDatabase.getDatabase(application).credentialDao()
        repository = CredentialRepository(credentialDao)
    }
    fun addCredential(credential: Credential){
        viewModelScope.launch(Dispatchers.IO){
            repository.addCredential(credential)
        }
    }
    fun updateCredential(credential: Credential){
        viewModelScope.launch(Dispatchers.IO){
            repository.updateCredential(credential)
        }
    }
    fun readAllData(userName: String, password: String){
        viewModelScope.launch(Dispatchers.IO){
            repository.readAllData(userName, password)
        }
    }

}

登录活动

class LoginActivity : AppCompatActivity() {
    private lateinit var mUserViewModel: CredentialViewModel
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_login)
        // Inflate the layout for this fragment


        mUserViewModel = ViewModelProvider(this).get(CredentialViewModel::class.java)
        val login = findViewById<Button>(R.id.login_btn)
        login?.setOnClickListener {
            val userName = username_txt.text.toString().trim();
            val password = password_txt.text.toString().trim();
            if(userName.isEmpty()||password.isEmpty()){
                Toast.makeText(
                    applicationContext,
                    "Please fill out all field!",
                    Toast.LENGTH_SHORT
                ).show()
            }else{
                mUserViewModel.readAllData(userName, password)
                if(user!=null){
                    Toast.makeText(applicationContext, "Successfully Login!", Toast.LENGTH_SHORT).show()

                    val intent = Intent(this@LoginActivity, MainActivity::class.java)
                    intent.putExtra("Username",userName)
                    startActivity(intent)
                }else{
                    Toast.makeText(applicationContext, "Wrong Password!", Toast.LENGTH_SHORT).show()
                }
            }

        }

    }

}

Answer 1

我觉得你CredentialRepository里面的readAllData()方法不对，因为这个函数需要把查询结果返回给CredentialViewModel。您正确的做法是将查询结果传递给ViewModel。

尝试登录时，还应调用ViewModel中定义的方法，并将username和password传递给该方法进行检索。最终结果定义了一个LiveData<Boolean>，表示是否登录成功。

class CredentialViewModel(application: Application): AndroidViewModel(application) {

    private val mResult = MutableLiveData<Credential>()

    val resultLiveData: LiveData<Credential> get() = mResult

    private val repository: CredentialRepository

    init{
        val credentialDao = CredentialDatabase.getDatabase(application).credentialDao()
        repository = CredentialRepository(credentialDao)
    }
    fun addCredential(credential: Credential){
        viewModelScope.launch(Dispatchers.IO){
            repository.addCredential(credential)
        }
    }
    fun updateCredential(credential: Credential){
        viewModelScope.launch(Dispatchers.IO){
            repository.updateCredential(credential)
        }
    }
    fun readAllData(userName: String, password: String){
        viewModelScope.launch(Dispatchers.IO){
            mResult.postValue(repository.readAllData(userName, password))
        }
    }

}

class LoginActivity : AppCompatActivity() {
    private lateinit var mUserViewModel: CredentialViewModel
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_login)
        // Inflate the layout for this fragment


        mUserViewModel = ViewModelProvider(this).get(CredentialViewModel::class.java)
        val login = findViewById<Button>(R.id.login_btn)
        mUserViewModel.resultLiveData.observe(this@LoginActivity, { credential ->
            if(credential!=null){
                Toast.makeText(applicationContext, "Successfully Login!", Toast.LENGTH_SHORT).show()

                val intent = Intent(this@LoginActivity, MainActivity::class.java)
                intent.putExtra("Username",userName)
                startActivity(intent)
            }else{
                Toast.makeText(applicationContext, "Wrong Password!", Toast.LENGTH_SHORT).show()
            }
        })

        login?.setOnClickListener {
            val userName = username_txt.text.toString().trim();
            val password = password_txt.text.toString().trim();
            if (userName.isEmpty() || password.isEmpty()) {
                Toast.makeText(
                    applicationContext,
                    "Please fill out all field!",
                    Toast.LENGTH_SHORT
                ).show()
            } else {
                mUserViewModel.readAllData(userName, password)
            }

        }
    }


}

修改存储库

class CredentialRepository(private val credentialDao: CredentialDao) {


    suspend fun addCredential(credential: Credential){
        credentialDao.addUser(credential)
    }
    suspend fun updateCredential(credential: Credential){
        credentialDao.updateUser(credential)
    }
    fun readAllData(username: String,password:String) :Credential{
        return credentialDao.readAllData(username,password)
    }
}