ButterKnife @OnClick annotation not working in Kotlin fragment

If you are using Kotlin, replace annotationProcessor with kapt

The reason behind it is that may be you are using dependencies like this :

dependencies {
  implementation 'com.jakewharton:butterknife:10.1.0'
  annotationProcessor 'com.jakewharton:butterknife-compiler:10.1.0'
}

replace it like this:

dependencies {
  implementation 'com.jakewharton:butterknife:10.1.0'
  kapt'com.jakewharton:butterknife-compiler:10.1.0'
}

Why don't you do it like this?

// get reference to button
val btn_click_me = findViewById(R.id.btn_click_me) as Button
// set on-click listener
btn_click_me.setOnClickListener {
    // your code to perform when the user clicks on the button
    Toast.makeText(this@MainActivity, "You clicked me.", Toast.LENGTH_SHORT).show()
}