Android MVVM

dark_plain_border_button.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:state_enabled="true">
        <ripple xmlns:android="http://schemas.android.com/apk/res/android" android:color="?colorControlHighlight">
            <item>
                <shape android:shape="rectangle">
                    <stroke android:width="1dp" android:color="@color/white" />
                    <solid android:color="?android:windowBackground" />
                </shape>
            </item>
        </ripple>
    </item>
    <item>
        <shape android:shape="rectangle">
            <stroke android:width="1dp" android:color="@color/grey_disabled" />
            <solid android:color="?android:windowBackground" />
        </shape>
    </item>
</selector>

EmailSignInViewModel.kt

class EmailSignInViewModel : GuestRxViewModel(), EmailSignInContract.ViewModel {

    override fun onEmailUpdate(input: Editable) {
        val email = input.toString()
        if (InputUtils.isValidEmail(email)) {
            emailError.set("")
        } else {
            emailError.set(getApplicationString(R.string.auth_error_invalid_email))
        }
        emailSubject.onNext(email)
    }

    override fun onPasswordUpdate(input: Editable) {
        val password = input.toString()
        if (InputUtils.isValidPassword(password)) {
            passwordError.set("")
        } else {
            passwordError.set(getApplicationString(R.string.auth_error_invalid_password))
        }
        passwordSubject.onNext(password)
    }

    override val emailError: ObservableField<String> = ObservableField("")
    override val passwordError: ObservableField<String> = ObservableField("")

    override val submitEnable = ObservableField<Boolean>(false)

    override fun email(): String = emailSubject.value
    override fun password(): String = passwordSubject.value

    protected val emailSubject: BehaviorSubject<String> = BehaviorSubject.create()
    protected val passwordSubject: BehaviorSubject<String> = BehaviorSubject.create()

    open fun init() {
        addDisposables(
                Observable
                        .combineLatest(emailSubject, passwordSubject, BiFunction<String, String, Pair<String, String>> { email, password -> return@BiFunction Pair(email, password) })
                        .subscribe({
                            (email, password) ->
                            submitEnable.set(InputUtils.isValidEmail(email) && InputUtils.isValidPassword(password))
                        })
        )
    }
}

fragment_email_sign_in.xml

<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>

        <variable
            name="view"
            type="com.acciio.homeapp.ui.auth.sign.email.EmailSignInContract.View" />

        <variable
            name="vm"
            type="com.acciio.homeapp.ui.auth.sign.email.EmailSignInContract.ViewModel" />

    </data>

    <android.support.constraint.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:paddingLeft="40dp"
        android:paddingRight="40dp"
        tools:context="com.acciio.homeapp.ui.auth.sign.email.EmailSignInFragment">

        <android.support.design.widget.TextInputLayout
            android:id="@+id/email_auth_text_email"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            app:error="@{vm.emailError}"
            app:errorEnabled="true"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent">

            <android.support.design.widget.TextInputEditText
                android:id="@+id/email_auth_edit_text_email"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:afterTextChanged="@{vm::onEmailUpdate}"
                android:hint="@string/auth_hint_email_address"
                android:inputType="textEmailAddress" />
        </android.support.design.widget.TextInputLayout>

        <android.support.design.widget.TextInputLayout
            android:id="@+id/email_auth_text_password"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            app:error="@{vm.passwordError}"
            app:errorEnabled="true"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/email_auth_text_email">

            <android.support.design.widget.TextInputEditText
                android:id="@+id/email_auth_edit_text_password"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:afterTextChanged="@{vm::onPasswordUpdate}"
                android:hint="@string/auth_hint_email_password"
                android:inputType="textPassword" />
        </android.support.design.widget.TextInputLayout>

        <Button
            android:id="@+id/email_auth_button"
            style="@style/DarkPlainBorderButton"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            android:enabled="@{safeUnbox(vm.submitEnable)}"
            android:onClick="@{(v) -> view.onEmailAuth(vm.email(), vm.password())}"
            android:text="@string/auth_sign_in_email"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/email_auth_text_password" />

        <Button
            android:id="@+id/button6"
            style="@style/DarkPlainBorderlessButton"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginBottom="16dp"
            android:onClick="@{(v)->view.onPasswordReset()}"
            android:text="@string/auth_email_password_find"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.5"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/email_auth_button"
            app:layout_constraintVertical_bias="1.0"
            tools:layout_editor_absoluteX="8dp"
            tools:layout_editor_absoluteY="566dp" />
    </android.support.constraint.ConstraintLayout>
</layout>