DefaultSpinner.java

package com.thomasdh.roosterpgplus.CustomUI;

import android.content.Context;
import android.support.v7.widget.AppCompatSpinner;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.SpinnerAdapter;
import android.widget.TextView;

import com.thomasdh.roosterpgplus.R;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

@SuppressWarnings("UnusedDeclaration")
public class DefaultSpinner extends AppCompatSpinner {

    public DefaultSpinner(Context context) {
        super(context);
    }

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

    public DefaultSpinner(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    public void setAdapter(SpinnerAdapter orig ) {
        SpinnerAdapter adapter = newProxy(orig);

        super.setAdapter(adapter);

        try {
            Method m = AdapterView.class.getDeclaredMethod(
                    "setNextSelectedPositionInt",int.class);
            m.setAccessible(true);
            m.invoke(this,-1);

            Method n = AdapterView.class.getDeclaredMethod(
                    "setSelectedPositionInt",int.class);
            n.setAccessible(true);
            n.invoke(this,-1);
        }
        catch( Exception e ) {
            throw new RuntimeException(e);
        }
    }

    protected SpinnerAdapter newProxy(SpinnerAdapter obj) {
        return (SpinnerAdapter) java.lang.reflect.Proxy.newProxyInstance(
                obj.getClass().getClassLoader(),
                new Class[]{SpinnerAdapter.class},
                new SpinnerAdapterProxy(obj));
    }



    /**
     * Intercepts getView() to display the prompt if position < 0
     */
    protected class SpinnerAdapterProxy implements InvocationHandler {

        protected SpinnerAdapter obj;
        protected Method getView;


        protected SpinnerAdapterProxy(SpinnerAdapter obj) {
            this.obj = obj;
            try {
                getView = SpinnerAdapter.class.getMethod(
                        "getView",int.class,View.class,ViewGroup.class);
            }
            catch( Exception e ) {
                throw new RuntimeException(e);
            }
        }

        public Object invoke(Object proxy, Method m, Object[] args) throws Throwable {
            try {
                return m.equals(getView) &&
                        (Integer) args[0] < 0 ?
                        getView((Integer)args[0],(View)args[1],(ViewGroup)args[2]) :
                        m.invoke(obj, args);
            }
            catch (InvocationTargetException e) {
                throw e.getTargetException();
            }
            catch (Exception e) {
                throw new RuntimeException(e);
            }
        }

        protected View getView(int position, View convertView, ViewGroup parent)
                throws IllegalAccessException {

            if( position<0 ) {
                TextView v = (TextView) LayoutInflater.from(getContext()).inflate(R.layout.spinner_title, parent, false);
                v.setText(getPrompt());
                return v;
            }
            return obj.getView(position,convertView,parent);
        }
    }
}