using Android.App;
using Android.OS;
using Android.Widget;

namespace SpinnerDemo
{
  [Activity(Label = "@string/ApplicationName", MainLauncher = true, Icon = "@drawable/icon")]
  public class MainActivity : Activity
  {
    private Spinner _citySpinner;
    private TextView _cityNameView;
    private ArrayAdapter<string> _cityInfos;

   
    protected override void OnCreate(Bundle bundle)
    {
      base.OnCreate(bundle);

      SetContentView(Resource.Layout.Main);
      _citySpinner = FindViewById<Spinner>(Resource.Id.sp_city);
      _cityNameView = FindViewById<TextView>(Resource.Id.txt_cityName);

      _cityInfos = new ArrayAdapter<string>(this, Android.Resource.Layout.SimpleSpinnerDropDownItem);
      _cityInfos.Add("成都");
      _cityInfos.Add("蘭州");
      _cityInfos.Add("武漢");
      _cityInfos.Add("上海");
      _citySpinner.Adapter = _cityInfos;
      _citySpinner.ItemSelected += CitySelectedEvent;
    }

    private void CitySelectedEvent(object sender, AdapterView.ItemSelectedEventArgs e)
    {
      _cityNameView.Text = _cityInfos.GetItem(e.Position);
    }
  }
}

package com.example.halower.spinnerdemo;

import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.TextView;
public class MainActivity extends ActionBarActivity {
  private Spinner _citySpinner;
  private TextView _cityNameView;
  private ArrayAdapter<String> _cityInfo;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    _citySpinner =(Spinner)findViewById(R.id.sp_city);
    _cityNameView =(TextView) findViewById(R.id.txt_cityName);

    _cityInfo =new ArrayAdapter<>(this,R.layout.support_simple_spinner_dropdown_item);
    _cityInfo.add("成都");
    _cityInfo.add("蘭州");
    _cityInfo.add("武漢");
    _cityInfo.add("上海");
    _citySpinner.setAdapter(_cityInfo);
    _citySpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
      @Override
      public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        _cityNameView.setText(_cityInfo.getItem(position));
      }

      @Override
      public void onNothingSelected(AdapterView<?> parent) {

      }
    });
  }
}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
  android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
  android:paddingRight="@dimen/activity_horizontal_margin"
  android:paddingTop="@dimen/activity_vertical_margin"
  android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

  <Spinner
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/sp_city"
    android:layout_alignParentTop="true"
    android:layout_alignParentRight="true"
    android:layout_alignParentEnd="true"
    android:layout_toEndOf="@+id/txt_cityName"
    android:layout_toRightOf="@+id/txt_cityName" />
  <TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="城市"
    android:id="@+id/txt_cityName"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />
</RelativeLayout>