与模态类的 LiveData 对象的双向数据绑定

Question

我正在尝试使用模态类的 LiveData 对象创建双向数据绑定连接。但是当我尝试读取用户的值时，结果是空的。这是我的代码-

class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    
    val viewModal: MainActivityViewModal = ViewModelProvider(
        this,
        MainActivityViewModalFactory()
    ).get(MainActivityViewModal::class.java)

    val binding = DataBindingUtil.setContentView<ActivityMainBinding>(
        this,
        R.layout.activity_main
    ).apply {
        this.lifecycleOwner = this@MainActivity
        this.viewModal = viewModal
    }
}}

这是布局文件-

<data>

    <variable
        name="viewModal"
        type="com.weaponx.databindingexample.MainActivityViewModal" />
</data>

<androidx.constraintlayout.widget.ConstraintLayout 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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <ImageView
        android:id="@+id/ivLogo"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:contentDescription="@string/logo"
        android:tint="#000000"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@android:drawable/ic_menu_myplaces" />

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/clBody"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/ivLogo">


        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/guideline1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            app:layout_constraintGuide_percent="0.10" />


        <com.google.android.material.textfield.TextInputLayout
            android:id="@+id/tilUserName"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:background="@drawable/edit_text_bg"
            android:hint="@string/user_name"
            android:padding="5dp"
            app:layout_constraintEnd_toStartOf="@id/guideline2"
            app:layout_constraintStart_toEndOf="@id/guideline1"
            app:layout_constraintTop_toTopOf="parent">

            <com.google.android.material.textfield.TextInputEditText
                android:id="@+id/tietUserName"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:background="@null"
                android:inputType="text"
                android:text="@={viewModal.user.userName}" />
        </com.google.android.material.textfield.TextInputLayout>

        <com.google.android.material.textfield.TextInputLayout
            android:id="@+id/tilPassword"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dp"
            android:background="@drawable/edit_text_bg"
            android:hint="@string/password"
            android:padding="5dp"
            app:layout_constraintEnd_toStartOf="@id/guideline2"
            app:layout_constraintStart_toEndOf="@id/guideline1"
            app:layout_constraintTop_toBottomOf="@id/tilUserName">

            <com.google.android.material.textfield.TextInputEditText
                android:id="@+id/tietPassword"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:background="@null"
                android:inputType="textPassword"
                android:text="@={viewModal.user.password}" />
        </com.google.android.material.textfield.TextInputLayout>


        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="80dp"
            android:background="@drawable/button_bg"
            android:text="@string/login"
            android:onClick="@{() -> viewModal.login()}"
            android:textAllCaps="false"
            android:textColor="@android:color/white"
            android:textSize="18sp"
            app:layout_constraintEnd_toStartOf="@id/guideline2"
            app:layout_constraintStart_toEndOf="@id/guideline1"
            app:layout_constraintTop_toBottomOf="@id/tilPassword" />

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/guideline2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            app:layout_constraintGuide_percent="0.90" />
    </androidx.constraintlayout.widget.ConstraintLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

这里是 ViewModal

class MainActivityViewModal : ViewModel() {
var user = MutableLiveData<User>()

fun login() {
    println("Login Success ${user.value}")
}}

这里是模态类

class User() {
var userName: String = ""
var password: String = ""

override fun toString(): String {
    return "User(userName='$userName', password='$password')"
}}

请告诉我解决此问题的任何解决方案或好方法

Answer 1

在MainActivityViewModal 中将user 定义为User 类型而不是MutableLiveData。