Based on EditText and ListPopupWindow

DropDownSpinner.java

import android.content.Context;
import android.graphics.Rect;
import android.support.v7.widget.AppCompatEditText;
import android.support.v7.widget.ListPopupWindow;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.inputmethod.InputMethodManager;
import android.widget.AdapterView;
import android.widget.BaseAdapter;

// XXX AppCompatEditText is used as we want to use it with TextInputLayout and utilize its tinting and hint feature
// style it with @style/Widget.AppCompat.Spinner.Underlined
public class DropDownSpinner extends AppCompatEditText {

    private ListPopupWindow listPopupWindow;
    private BaseAdapter adapter;
    private AdapterView.OnItemSelectedListener onItemSelectedListener;
    private ToString converter;

    public DropDownSpinner(Context context) {
        super(context, null);
        init();
    }

    public DropDownSpinner(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public DropDownSpinner(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        listPopupWindow = new ListPopupWindow(getContext());
        listPopupWindow.setAnchorView(this);
        listPopupWindow.setPromptPosition(ListPopupWindow.POSITION_PROMPT_ABOVE);
        listPopupWindow.setModal(true);
        listPopupWindow.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Object item = adapter.getItem(position);
                if (converter == null) {
                    setText(item.toString());
                } else {
                    setText(converter.convertToString(item));
                }
                if (onItemSelectedListener != null) {
                    onItemSelectedListener.onItemSelected(parent, view, position, id);
                }
                listPopupWindow.dismiss();
            }
        });
        listPopupWindow.setInputMethodMode(ListPopupWindow.INPUT_METHOD_NOT_NEEDED);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (MotionEvent.ACTION_UP == event.getAction()) {
            if (listPopupWindow.isShowing()) {
                listPopupWindow.dismiss();
            } else {
                requestFocus();
                listPopupWindow.setAdapter(adapter);
                listPopupWindow.show();
            }
        }
        return super.onTouchEvent(event);
    }

    @Override
    protected void onFocusChanged(boolean focused, int direction, Rect previouslyFocusedRect) {
        super.onFocusChanged(focused, direction, previouslyFocusedRect);
        if (focused) {
            InputMethodManager imm = (InputMethodManager) getContext().getSystemService(Context.INPUT_METHOD_SERVICE);
            imm.hideSoftInputFromWindow(getWindowToken(), 0);
            setKeyListener(null);
        }
    }

    public <T extends BaseAdapter & ToString> void setAdapter(T adapter, ToString converter) {
        this.adapter = adapter;
        this.converter = converter;
    }

    public void setOnItemSelectedListener(AdapterView.OnItemSelectedListener onItemSelectedListener) {
        this.onItemSelectedListener = onItemSelectedListener;
    }

    public interface ToString<T> {

        String convertToString(T object);

    }
}