CODEWITHSUNDEEP
javakotlin
Kumar Kalluri
Kumar Kalluri

Reputation: 513

How to emulate the same behaviour in kotlin

How to emulate the same behaviour using lambdas kotlin.

Java Code:

   public interface OnClickListener{
    public void onClick();
    }


    public class Sample {

            OnclickListener mOnclickListener;

            public void setOnclickListener(OnclickListener l){

                if(l!=null)
                mOnclickListener =l;
            }


            public void performClick()
            {
                mOnclickListener.onClick(5);
            }

        }

  public class SampleImpl{

     Sample sample=new Sample();
      sample.setOnClickListener(new OnClickListner(){ onClick{}});

     sample.performClick();

}

As per kotlin, function receives parameter of interface with single method can represent in lambda, i am trying...

Kotlin code :

var sample= Sample();

    sample.setOnClickListener({Int ->  println("action performed") })
    sample.performClick(); //will call this method whenever needed.


    class Sample {

         var click=null;

        fun setOnClickListener(onClick : (Int)->Unit){

           click= onClick // trying to assign and want to use it in another 
                              funciton. I know it is wrong, how to achieve 
                             this.
        }

      fun performClick()
       {
           click(5)
       }
    }

Is there any alternative to achieve this?

Upvotes: 1

Views: 115

Answers (3)

Komang Sidhi Artha
Komang Sidhi Artha

Reputation: 321

I know it already answered, but if you want to stick with null declaration of click variable, you can write it like:

class Sample {
    var click: ((Int)->Unit)? = null

    fun setOnClickListener(onClick : (Int)->Unit) {
        click = onClick
    }

    fun performClick() {
        click?.invoke(5)
    }
}

Hope it can help anyone

Upvotes: 0

Gowtham Subramaniam
Gowtham Subramaniam

Reputation: 3478

Alterantively you can try this:

interface OnClickListener {
        fun onClick()
    }


    inner class Sample {

        internal var mOnclickListener: OnClickListener

        fun setOnclickListener(l: OnClickListener?) {

            if (l != null)
                mOnclickListener = l
        }


        fun performClick() {
            mOnclickListener.onClick(5)
        }

    }

    inner class SampleImpl internal constructor() {

        internal var sample = Sample()

        init {
            onClick
            run { }
        }

    }

Upvotes: 0

Michael
Michael

Reputation: 58437

The compiler has no way of inferring a type of (Int) -> Unit from var click = null.

You can change the declaration to something like var click : (Int) -> Unit = {}. This explicitly states the type, and uses a non-nullable type so as not to complicate performClick.

Upvotes: 4

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