How to reference anonymous inner class in Kotlin?

Question

I have following extension method. How can I reference the OnGlobalLayoutListener that is passed into the addOnGLobalLayoutListener() method? I need to pass the listener to the removeOnGlobalLayoutListener() method.

fun View.OnGlobalLayout(callback:() -> Unit ): Unit{
    this.viewTreeObserver.addOnGlobalLayoutListener {
        if(android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.JELLY_BEAN) {
            this.viewTreeObserver.removeOnGlobalLayoutListener(this);
        }
        else {
            this.viewTreeObserver.removeGlobalOnLayoutListener(this);
        }
        callback();
    }
}

See also http://stackoverflow.com/questions/38074356/kotlin-recommended-way-of-unregistering-a-listener-with-a-sam — yole, Jun 29 '16 at 14:53

miensol · Answer 1 · 2016-06-29T13:34:16.603

One way is to use object expression instead of lambda like so:

fun View.OnGlobalLayout(callback: () -> Unit): Unit {
    val viewTreeObserver = this.viewTreeObserver
    viewTreeObserver.addOnGlobalLayoutListener(object : ViewTreeObserver.OnGlobalLayoutListener {
        override fun onGlobalLayout() {
            if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.JELLY_BEAN) {
                viewTreeObserver.removeOnGlobalLayoutListener(this);
            } else {
                viewTreeObserver.removeGlobalOnLayoutListener(this);
            }
            callback();
        }
    })
}

How to reference anonymous inner class in Kotlin?

1 Answers1