title: Android data binding problem: "Cause: couldn't make a guess for"
body: <p>i'm enabling data binding with adding </p>
  
  <blockquote>
    <p>dataBinding {
            enabled = true
        }</p>
  </blockquote>
  
  <p>and </p>
  
  <blockquote>
    <p>kapt 'com.android.databinding:compiler:3.1.4'</p>
  </blockquote>
  
  <p>in app level <code>build.gradle</code> file.</p>
  
  <blockquote>
    <p>apply plugin: 'kotlin-kapt'</p>
  </blockquote>
  
  <p>is added top of that.  project is based on kotlin . </p>
  
  <p>here is my model: </p>
  
  <pre><code>    package ir.app.myapplication;
  
  
  
  data class cisclass(val equRevId:String)
  </code></pre>
  
  <p>main Activity :</p>
  
  <pre><code>  val binding: ActivityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main)
  
          val user = cisclass("123")
          binding.setVariable(BR.cis, user)
          binding.executePendingBindings()
  </code></pre>
  
  <p>here is my layout:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  
  &lt;layout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:tools="http://schemas.android.com/tools"
      &gt;
  
      &lt;data&gt;
  
          &lt;variable
              name="cis"
              type="ir.app.myapplication.cisclass" /&gt;
      &lt;/data&gt;
  
      &lt;androidx.core.widget.NestedScrollView
  
  
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:layout_margin="5dp"
          android:orientation="vertical"
          android:scrollbars="vertical"&gt;
  
  
          &lt;LinearLayout
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:orientation="vertical"&gt;
  
  
  
                      &lt;TextView
                          android:text="@{cis.equRevId}"
                          android:layout_width="wrap_content"
                          android:layout_height="wrap_content"
                          android:textStyle="bold"
  
                          /&gt;
  
  
          &lt;/LinearLayout&gt;
  
  
      &lt;/androidx.core.widget.NestedScrollView&gt;
  
  &lt;/layout&gt;
  </code></pre>
  
  <p>i will got this error: </p>
  
  <pre><code>java.lang.IllegalArgumentException: couldn't make a guess for ir.meedc.myapplication.cisclass
      at com.squareup.javapoet.Util.checkArgument(Util.java:64)
      at com.squareup.javapoet.ClassName.bestGuess(ClassName.java:171)
      at android.databinding.tool.ext.ExtKt.toTypeName(ext.kt:244)
      at android.databinding.tool.ext.ExtKt.toTypeName(ext.kt:192)
      at android.databinding.tool.ext.ExtKt.toTypeName(ext.kt:173)
      at android.databinding.tool.writer.BaseLayoutBinderWriter.createVariableFields(BaseLayoutBinderWriter.kt:229)
      at android.databinding.tool.writer.BaseLayoutBinderWriter.access$createVariableFields(BaseLayoutBinderWriter.kt:39)
      at android.databinding.tool.writer.BaseLayoutBinderWriter$createType$1.invoke(BaseLayoutBinderWriter.kt:67)
      at android.databinding.tool.writer.BaseLayoutBinderWriter$createType$1.invoke(BaseLayoutBinderWriter.kt:39)
      at android.databinding.tool.ext.Javapoet_extKt.classSpec(javapoet_ext.kt:39)
      at android.databinding.tool.writer.BaseLayoutBinderWriter.createType(BaseLayoutBinderWriter.kt:63)
      at android.databinding.tool.writer.BaseLayoutBinderWriter.write(BaseLayoutBinderWriter.kt:59)
      at android.databinding.tool.BaseDataBinder.generateAll(BaseDataBinder.kt:65)
      at com.android.build.gradle.internal.tasks.databinding.DataBindingGenBaseClassesTask$CodeGenerator.run(DataBindingGenBaseClassesTask.kt:212)
      at com.android.build.gradle.internal.tasks.databinding.DataBindingGenBaseClassesTask$writeBaseClasses$$inlined$recordTaskAction$1.invoke(AndroidVariantTask.kt:52)
      at com.android.build.gradle.internal.tasks.databinding.DataBindingGenBaseClassesTask$writeBaseClasses$$inlined$recordTaskAction$1.invoke(AndroidVariantTask.kt:31)
      at com.android.build.gradle.internal.tasks.Blocks.recordSpan(Blocks.java:91)
  </code></pre>
  
  <p>how can i fix that? whats the problem?</p>