Dismissing an alert dialog with custom Anko layout DSL

I have created the following alert dialog with a simple view comprising of a TextView, EditText and Button:

alert {
            customView {
                verticalLayout {
                    textView {
                        text = getString(R.string.enter_quantity)
                        textSize = 18f
                        textColor = Color.BLACK
                    }.lparams {
                        topMargin = dip(17)
                        horizontalMargin = dip(17)
                        bottomMargin = dip(10)
                    }

                    val quantity = editText {
                        inputType = InputType.TYPE_CLASS_NUMBER
                        background = ContextCompat.getDrawable(this@ProductsList, R.drawable.textbox_bg)
                    }.lparams(width = matchParent, height = wrapContent) {
                        bottomMargin = dip(10)
                        horizontalMargin = dip(17)
                    }

                    button(getString(R.string.confirm)) {
                        background = ContextCompat.getDrawable(this@ProductsList, R.color.colorPrimary)
                        textColor = Color.WHITE
                    }.lparams(width = matchParent, height = matchParent) {
                        topMargin = dip(10)
                    }.setOnClickListener {
                        if (quantity.text.isNullOrBlank())
                            snackbar(parentLayout!!, getString(R.string.enter_valid_quantity))
                        else
                            addToCart(product, quantity.text.toString().toInt())
                    }
                }
            }
        }.show()

I want to dismiss it whenever the button is clicked and the if-else clause has been executed. I tried using this@alert but it doesn't provide the dialog methods.

This is problematic because your button function call which registers the listener executes when the dialog doesn't even exist yet.

Here's one way to do it, using a local lateinit variable to make the dialog available inside the listener:

lateinit var dialog: DialogInterface
dialog = alert {
    customView {
        button("Click") {
            dialog.dismiss()
        }
    }
}.show()

You could also assign the result of the builder to a class property, etc. Note that lateinit for local variables is available since Kotlin 1.2.