title: Bindable must be on a member in an Observable class
body: <p>I'm new in data binding , this is my code but I get this error on building </p>
  
  <pre><code>class DatabindingViewModel :ViewModel() {
  
  val currentFruitName:LiveData&lt;String&gt;
      get() = FakeRepository.currentName
  
  fun changeNameOnClick()=FakeRepository.changeRandomFoodName()
  
  //two way LiveData
  @Bindable
  val editTextContext= MutableLiveData&lt;String&gt;()
  
  private val _displayEditTexfContent=MutableLiveData&lt;String&gt;()
  val displayEditTexfContent:LiveData&lt;String&gt;
      get()=_displayEditTexfContent
  
  fun onDisplayEtText(){
      _displayEditTexfContent.value=editTextContext.value
  }
  </code></pre>
  
  <p>this is my xml layout code :</p>
  
  <pre><code>    &lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;layout xmlns:app="http://schemas.android.com/apk/res-auto"
      xmlns:tools="http://schemas.android.com/tools"
      xmlns:android="http://schemas.android.com/apk/res/android"&gt;
  
      &lt;data&gt;
          &lt;variable
              name="binding"
              type="ir.persiandesigners.myapplication.databinding.viewmodel.DatabindingViewModel" /&gt;
      &lt;/data&gt;
  
      &lt;androidx.constraintlayout.widget.ConstraintLayout
          android:id="@+id/linearLayout"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:orientation="vertical"&gt;
  
          &lt;TextView
              android:id="@+id/textView"
              android:layout_width="0dp"
              android:layout_height="wrap_content"
              android:layout_marginStart="50dp"
              android:layout_marginLeft="50dp"
              android:layout_marginTop="32dp"
              android:layout_marginEnd="50dp"
              android:layout_marginRight="50dp"
              android:text="@{binding.currentFruitName}"
              android:textAppearance="@style/TextAppearance.AppCompat.Display1"
              app:layout_constraintEnd_toEndOf="parent"
              app:layout_constraintStart_toStartOf="parent"
              app:layout_constraintTop_toTopOf="parent" /&gt;
  
          &lt;Button
              android:id="@+id/button"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:layout_marginTop="32dp"
              android:onClick="@{()-&gt;binding.changeNameOnClick()}"
              android:text="Get Random  Name"
              app:layout_constraintEnd_toEndOf="parent"
              app:layout_constraintStart_toStartOf="parent"
              app:layout_constraintTop_toBottomOf="@+id/textView" /&gt;
  
          &lt;EditText
              android:id="@+id/editText"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:layout_marginStart="8dp"
              android:layout_marginLeft="8dp"
              android:layout_marginTop="60dp"
              android:layout_marginEnd="8dp"
              android:layout_marginRight="8dp"
              android:ems="10"
              android:inputType="textPersonName"
              android:text="@={binding.editTextContext}"
              app:layout_constraintEnd_toEndOf="parent"
              app:layout_constraintStart_toStartOf="parent"
              app:layout_constraintTop_toBottomOf="@+id/button" /&gt;
  
          &lt;Button
              android:id="@+id/button2"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:layout_marginStart="8dp"
              android:layout_marginLeft="8dp"
              android:layout_marginTop="24dp"
              android:layout_marginEnd="8dp"
              android:layout_marginRight="8dp"
              android:onClick="@{()-&gt;binding.onDisplayEtText()}"
              android:text="Change Display Text"
              app:layout_constraintEnd_toEndOf="parent"
              app:layout_constraintStart_toStartOf="parent"
              app:layout_constraintTop_toBottomOf="@+id/editText" /&gt;
      &lt;/androidx.constraintlayout.widget.ConstraintLayout&gt;
  
  &lt;/layout&gt;
  </code></pre>
  
  <p>this is the code I've in the activity: </p>
  
  <pre><code>val viweModel= ViewModelProviders.of(this)
              .get(DatabindingViewModel::class.java)
  
      DataBindingUtil.setContentView&lt;ActvitiyDatadindingBinding&gt;(
              this,R.layout.actvitiy_datadinding)
              .apply {
                  this.setLifecycleOwner( this@DataBindingAct)
                  this.binding=viweModel
              }
  
      viweModel.editTextContext.observe(this, Observer{
          Toast.makeText(this@DataBindingAct,it ,Toast.LENGTH_LONG).show()
      })
  </code></pre>
  
  <p>when I want to build the project and run it , I get this error : </p>
  
  <pre><code>e: error: Bindable must be on a member in an Observable class. DatabindingViewModel is not Observable
  </code></pre>
  
  <p>could you help me ? </p>
  
  <p>I've tried to clean the project , rebuild and so on but there is an error in my code that I couldn't find </p>
  
  <p>could you help me ? </p>