Spinner

<resources>
    <string name="app_name">HelloWorld</string>

    <string-array name="city_labels">
        <item>北京</item>
        <item>上海</item>
        <item>广州</item>
        <item>深圳</item>
    </string-array>
</resources>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical"
    tools:context="com.pingyijinren.helloworld.MainActivity">

    <Spinner
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:entries="@array/city_labels"
        android:id="@+id/spinner"></Spinner>
</LinearLayout>

package com.pingyijinren.helloworld;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Spinner;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener {
    private Spinner spinner;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        spinner=(Spinner)findViewById(R.id.spinner);
        spinner.setPrompt("选择你所在的城市");
        spinner.setOnItemSelectedListener(this);
    }

    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        String[] cities=getResources().getStringArray(R.array.city_labels);
        Toast.makeText(this,cities[position]+"",Toast.LENGTH_SHORT).show();
    }

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