InstantAutoComplete

import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.widget.AutoCompleteTextView;

public class InstantAutoComplete extends AutoCompleteTextView {
	public InstantAutoComplete(Context context) {
		super(context);
	}

	public InstantAutoComplete(Context arg0, AttributeSet arg1) {
		super(arg0, arg1);
	}

	public InstantAutoComplete(Context arg0, AttributeSet arg1, int arg2) {
		super(arg0, arg1, arg2);
	}

	@Override
	public boolean enoughToFilter() {
		return true;
	}

	@Override
	protected void onFocusChanged(boolean focused, int direction, Rect previouslyFocusedRect) {
		super.onFocusChanged(focused, direction, previouslyFocusedRect);
		
		if (getWindowVisibility() == View.GONE) {
			Log.d("InstantAutoComplete", "Window not visible, will not show drop down");
			return;
		}
		
		if (focused) {
			performFiltering(getText(), 0);
			showDropDown();
		}
	}
}

This silently ignores the situation when focus gets restored on configuration change. I've ended up using View#post:

class InstantAutoComplete(context: Context) : AutoCompleteTextView(context) {
    override fun enoughToFilter(): Boolean = true
    override fun onFocusChanged(focused: Boolean, direction: Int, previouslyFocusedRect: Rect?) {
        super.onFocusChanged(focused, direction, previouslyFocusedRect)
        if (focused && adapter != null)
             if (!maybeShowSuggestions())
                 post { maybeShowSuggestions() }
    }
    private fun maybeShowSuggestions(): Boolean =
        if (windowVisibility == View.VISIBLE) {
            performFiltering(text, 0)
            showDropDown()
            true
        } else {
            false
        }
}