ButterKnife: @BindView but get error saying that button instance variable is not initialized

Question

I am using ButterKnife to bind view element.

Here is my fragment layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    ...

    <Button
        android:id="@+id/ok_btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/ok" />
</LinearLayout>

My fragment:

class MyFragment : Fragment() {
    @BindView(R.id.ok_btn)
    lateinit var okBtn: Button

    ...

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        okBtn.setOnClickListener { view ->
            Log.d("mytag", "ok clicked!")
        }
    }
}

When I run my simple app, I get error:

Caused by: kotlin.UninitializedPropertyAccessException: lateinit property okBtn has not been initialized
E/AndroidRuntime( 5435):    at com.my.app.MyFragment.onViewCreated(MyFragment.kt:35)

Why I get this error? It sounds like the @BindView(R.id.ok_btn) does't initialize the button instance variable. What do I miss?

Answer 1

where is the line like?

Butterknife.bind(this, rootView) 

not sure how it should look on Kotlin
and don't forget to add unbinder
you should use it with fragments according documentation

finally it will look something like...

Unbinder unbinder;
onViewCreated(){ 
  unbinder = Butterknife.bind(this, rootView); 
  //here you can set your onClickListener
}
onDestroyView(){
  unbinder.unbind()
}

adapt it for Kotlin and bravely use))