compare room database valuw with user input

Question

How can I compare the value from the room database with the text field? I want to compare the user input value with the credential view model but I have no idea how to do it. I have already set the query in the credentialDao so the value fetched should be inside the view model. But I just could not compare it. CredentialDao

@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
}

CredentialDatabase

@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
            }
        }
    }

}

Credential Repository

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)
    }
}

CredentialViewModel

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)
        }
    }

}

LoginActivity

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

I think the readAllData() method in your CredentialRepository is incorrect, because this function needs to return the query result to CredentialViewModel. Your correct approach is to pass the query result to ViewModel.

When trying to log in, you should also call the method defined in ViewModel and pass username and password to this method for retrieval. The final result defines a LiveData<Boolean> to represent whether you log in successfully.

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)
            }

        }
    }


}

modify Repository

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)
    }
}