androidkotlinmvvmdata-bindingviewmodel
The expression cannot be inverted, to be used in a two-way binding in EditText error
It is my first time using data binding, so I'm confused. Trying to implement two-way databinding in EditText with MVVM architecture and getting this error in my Build:
The expression 'viewmodelClientUrl.getValue()' cannot be inverted, so it cannot be used in a two-way binding
Details: There is no inverse for method getValue, you must add an @InverseMethod annotation to the method to indicate which method should be used when using it in two-way binding expressions
I can't understand what it means
There is my LoginViewModel:
class LoginViewModel(
private val repository: MainRepository): ViewModel() {
private var _clientUrl = MutableLiveData<String?>()
private var _username = MutableLiveData<String?>()
private var _password = MutableLiveData<String?>()
private val validationError = ValidationError()
val clientUrl: LiveData<String?>
get() = _clientUrl
val username: LiveData<String?>
get() = _username
val password: LiveData<String?>
get() = _password
fun onClick(){
val clientUrl = clientUrl.toString().trim()
val username = username.toString().trim()
val password = password.toString().trim()
validateCredentials(clientUrl, username, password)
}
private fun validateCredentials(clientUrl: String, username: String, password: String): Boolean {
if(!Patterns.WEB_URL.matcher(clientUrl).matches() || clientUrl.isEmpty()) {
validationError.isUrlValid = false
return false
}
if(username.isEmpty()) {
validationError.isUsernameValid = false
return false
}
if(password.isEmpty()) {
validationError.isUsernameValid = false
return false
}
return true
}
There is my layout:
<layout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<data>
<import type="android.view.View"/>
<variable
name="viewmodel"
type="com.example.redmining.ui.login.LoginViewModel"/>
<variable
name="validationError"
type="com.example.redmining.model.ValidationError"/>
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="16dp"
tools:context=".ui.login.LoginFragment"
android:background="@color/white">
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/urlTextInputLayout"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="24dp"
android:layout_marginTop="170dp"
android:layout_marginEnd="24dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<com.google.android.material.textfield.TextInputEditText
android:id="@+id/clientUrl"
android:text="@={viewmodel.clientUrl}"
android:fontFamily="@font/poppins_light"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/url_hint"
android:inputType="textUri"
android:selectAllOnFocus="true"
/>
</com.google.android.material.textfield.TextInputLayout>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintTop_toBottomOf="@id/urlTextInputLayout"
app:layout_constraintStart_toStartOf="@id/urlTextInputLayout"
android:text="Invalid URL"
android:textColor="@android:color/holo_red_light"
android:textSize="12sp"
android:layout_marginTop="-8dp"
android:layout_marginStart="5dp"
android:visibility="@{validationError.urlValid ? View.GONE : View.VISIBLE}"/>
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/usernameTextInputLayout"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="24dp"
android:layout_marginTop="4dp"
android:layout_marginEnd="24dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@id/urlTextInputLayout">
<com.google.android.material.textfield.TextInputEditText
android:id="@+id/username"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:fontFamily="@font/poppins_light"
android:hint="@string/login"
android:inputType="textEmailAddress"
android:selectAllOnFocus="true"
android:text="@={viewmodel.username}" />
</com.google.android.material.textfield.TextInputLayout>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintTop_toBottomOf="@id/usernameTextInputLayout"
app:layout_constraintStart_toStartOf="@id/usernameTextInputLayout"
android:text="Enter your username"
android:textColor="@android:color/holo_red_light"
android:textSize="12sp"
android:layout_marginTop="-8dp"
android:layout_marginStart="5dp"
android:visibility="@{validationError.usernameValid ? View.GONE : View.VISIBLE}"/>
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/passwordTextInputLayout"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="24dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="24dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/usernameTextInputLayout"
app:passwordToggleEnabled="true">
<com.google.android.material.textfield.TextInputEditText
android:text="@={viewmodel.password}"
android:id="@+id/password"
android:fontFamily="@font/poppins_light"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/password"
android:imeActionLabel="@string/log_in"
android:imeOptions="actionDone"
android:inputType="textPassword"
android:selectAllOnFocus="true" />
</com.google.android.material.textfield.TextInputLayout>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintTop_toBottomOf="@id/passwordTextInputLayout"
app:layout_constraintStart_toStartOf="@id/passwordTextInputLayout"
android:text="Enter your password"
android:textColor="@android:color/holo_red_light"
android:textSize="12sp"
android:layout_marginTop="-8dp"
android:layout_marginStart="5dp"
android:visibility="@{validationError.passwordValid ? View.GONE : View.VISIBLE}"/>
<Button
android:onClick="@{() -> viewmodel.onClick()}"
android:id="@+id/login"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="48dp"
android:layout_marginEnd="48dp"
android:layout_marginTop="16dp"
android:backgroundTint="@color/black"
android:enabled="true"
android:fontFamily="@font/poppins_light"
android:paddingLeft="30dp"
android:paddingTop="20dp"
android:paddingRight="30dp"
android:paddingBottom="20dp"
android:text="@string/log_in"
android:textAllCaps="true"
android:textColor="@color/white"
android:textSize="18sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/passwordTextInputLayout"/>
</androidx.constraintlayout.widget.ConstraintLayout>
Solution
I think you don't need 2 way binding, because it will work fine without it.
android:text="@{viewmodel.clientUrl}"
Even if you need to use it then, there are 2 approaches :
1st approach :
Use MutableLiveData instead of LiveData, because LiveData doesn't provide setter.
make _clientUrl non-private and :
android:text="@{viewmodel._clientUrl}"
2nd approach :
If you want to use LiveData then use afterTextChanged to set the value :
in ViewModel :
fun updateClientUrl(s: Editable) {
_clientUrl.value = s.toString();
}
In XML :
android:text="@{viewmodel.clientUrl}"
android:afterTextChanged="@{viewmodel.updateClientUrl}"
All of the solutions will work :
