inline.kt

// declaration
inline fun inlineFunction(callback: () -> Unit) {
    println("before callback")
    callback()
    println("after callback")
}

// calling function
btnPrintMessage.setOnClickListener(){
    inlineFunction(){
        println("Inline function has been called")
    }
}

// calling function will be treated in java like this
btnPrintMessage.setOnClickListener(){
  @override 
  void OnClick(View v){
    println("before callback")
   
    // this is callback body in nonInlineFunction
    println("Inline function has been called")
    
    println("after callback")
  }
}