Android_Spinner实现下拉选择菜单

<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:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.zj.MainActivity" >
<TextView
android:id="@+id/textView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="25dp"
android:textColor="#ff0000"
/>

<Spinner
android:id="@+id/spinner"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView"
android:layout_below="@+id/textView"
android:layout_marginTop="37dp" />

</RelativeLayout>

package com.example.zj;

import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.TextView;

public class MainActivity extends Activity implements OnItemSelectedListener {
private TextView textView;
private Spinner spinner;
private List<String> list;
private ArrayAdapter adapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textView = (TextView) findViewById(R.id.textView);
spinner = (Spinner) findViewById(R.id.spinner);
textView.setText("你选择的城市是北京");
//1.设置数据源
list = new ArrayList<String>();
list.add("北京");
list.add("上海");
list.add("广州");
list.add("深圳");
//2.设置数组适配器（ArrayAdapter）
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, list);
//3.adapter设置一个下拉表样式
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
//4.spinner适配器
spinner.setAdapter(adapter);
//5.设置spinner监听器
spinner.setOnItemSelectedListener(this);
}

@Override
public void onItemSelected(AdapterView<?> parent, View view, int position,
long id) {
// TODO Auto-generated method stub
String city = (String) adapter.getItem(position);
//String city = list.get(position);
textView.setText("你选择的城市是"+city);
}

@Override
public void onNothingSelected(AdapterView<?> parent) {
// TODO Auto-generated method stub

}
}