为什么我无法从视图模型 class 中获取值？

Question

我想使用 mvvm 设计模式进行数据绑定。但是，我无法将数据导入我的视图模型 class 结果 returns null。最后，当我对 activity 执行相同操作时，我成功传输了数据，但是当我将其与预告片一起使用时，我遇到了问题。

片段class

class AddTenant : Fragment() {
private lateinit var viewModel : AddTenantVM
private lateinit var dataBinding : FragmentAddTenantBinding
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)


}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
                          savedInstanceState: Bundle?): View? {
    dataBinding = DataBindingUtil.inflate(inflater,R.layout.fragment_add_tenant,container,false)

    return dataBinding.root
}

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    viewModel = ViewModelProviders.of(this).get(AddTenantVM::class.java)
    dataBinding.addTenant=viewModel
    dataBinding.lifecycleOwner=this
    button.setOnClickListener {
        viewModel.tenant()
    }

}

}

XML class

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data>
    <variable
        name="addTenant"
        type="com.example.kiratakip.viewmodel.AddTenantVM" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".AddTenant">

<EditText
    android:id="@+id/editTextTextPersonName"
    android:layout_width="350dp"
    android:layout_height="wrap_content"
    android:layout_marginTop="17dp"
    android:ems="10"
    android:hint="Adı Soyadı"
    android:inputType="textPersonName"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.5"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    android:text="@{addTenant.name}"/>

<EditText
    android:id="@+id/editTextTextPersonName2"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginStart="31dp"
    android:layout_marginTop="7dp"
    android:layout_marginEnd="10dp"
    android:ems="10"
    android:hint="T.C"
    android:inputType="textPersonName"
    app:layout_constraintEnd_toStartOf="@+id/editTextTextPersonName3"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/editTextTextPersonName"
    android:text="@{addTenant.city}"
   />

<EditText
    android:id="@+id/editTextTextPersonName3"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginEnd="30dp"
    android:ems="10"
    android:hint="Telefon"
    android:inputType="textPersonName"
    app:layout_constraintBaseline_toBaselineOf="@+id/editTextTextPersonName2"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toEndOf="@+id/editTextTextPersonName2"
    android:text="@{addTenant.tc}"
   />

<EditText
    android:id="@+id/editTextTextPersonName4"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginStart="31dp"
    android:layout_marginTop="11dp"
    android:layout_marginEnd="10dp"
    android:ems="10"
    android:hint="İl"
    android:inputType="textPersonName"
    app:layout_constraintEnd_toStartOf="@+id/editTextTextPersonName5"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/editTextTextPersonName2"
    android:text="@{addTenant.telefon}"/>

<EditText
    android:id="@+id/editTextTextPersonName5"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginEnd="30dp"
    android:ems="10"
    android:hint="İlçe"
    android:inputType="textPersonName"
    app:layout_constraintBaseline_toBaselineOf="@+id/editTextTextPersonName4"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toEndOf="@+id/editTextTextPersonName4"
    android:text="@{addTenant.district}"/>

<EditText
    android:id="@+id/editTextTextPersonName6"
    android:layout_width="350dp"
    android:layout_height="wrap_content"
    android:layout_marginTop="13dp"
    android:ems="10"
    android:hint="Adres Detay"
    android:inputType="textPersonName"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.5"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/editTextTextPersonName5"
    android:text="@{addTenant.adress}"/>

<EditText
    android:id="@+id/editTextTextPersonName7"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginStart="31dp"
    android:layout_marginTop="9dp"
    android:layout_marginEnd="10dp"
    android:ems="10"
    android:hint="Kontrat Baslangıç"
    android:inputType="textPersonName"
    app:layout_constraintEnd_toStartOf="@+id/editTextTextPersonName8"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/editTextTextPersonName6"
    android:text="@{addTenant.contractStart}"/>

<EditText
    android:id="@+id/editTextTextPersonName8"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginEnd="30dp"
    android:ems="10"
    android:hint="Kontrart Bitiş"
    android:inputType="textPersonName"
    app:layout_constraintBaseline_toBaselineOf="@+id/editTextTextPersonName7"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toEndOf="@+id/editTextTextPersonName7"
    android:text="@{addTenant.contractFinish}"/>

<EditText
    android:id="@+id/editTextTextPersonName9"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginStart="31dp"
    android:layout_marginTop="11dp"
    android:layout_marginEnd="10dp"
    android:ems="10"
    android:hint="Kira Tutarı"
    android:inputType="textPersonName"
    app:layout_constraintEnd_toStartOf="@+id/editTextTextPersonName10"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/editTextTextPersonName7"
   />

<EditText
    android:id="@+id/editTextTextPersonName10"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginEnd="30dp"
    android:ems="10"
    android:hint="Depozito"
    android:inputType="textPersonName"
    app:layout_constraintBaseline_toBaselineOf="@+id/editTextTextPersonName9"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toEndOf="@+id/editTextTextPersonName9"
   />

<Button
    android:id="@+id/button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginTop="59dp"
    android:text="Oluştur"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.5"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/editTextTextPersonName10"
    />

  </androidx.constraintlayout.widget.ConstraintLayout>
  </layout>

视图模型class

class AddTenantVM(application: Application): BaseViewModel(application) {
val addTenant = MutableLiveData<HomeList>()
val name = MutableLiveData<String>()
val tc = MutableLiveData<String>()
val telefon = MutableLiveData<String>()
val city = MutableLiveData<String>()
val district = MutableLiveData<String>()
val adress = MutableLiveData<String>()
val contractStart = MutableLiveData<String>()
val contractFinish = MutableLiveData<String>()
fun tenant (){
    println(name.value.toString())

}

}

Answer 1

尝试在 return dataBinding.root

之前初始化视图模型

override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
                          savedInstanceState: Bundle?): View? {
    dataBinding = DataBindingUtil.inflate(inflater,R.layout.fragment_add_tenant,container,false)
    viewModel = ViewModelProviders.of(this).get(AddTenantVM::class.java)
    dataBinding.addTenant=viewModel
    dataBinding.lifecycleOwner=this
    return dataBinding.root
}

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    button.setOnClickListener {
        viewModel.tenant()
    }
}

为什么我无法从视图模型 class 中获取值？

Why can't I get the value from the view model class?

android

android-databinding

android-mvvm