<Spinner 
android:id="@+id/spinner1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
/>

String[] city=new String[]{"北京","上海","香港","澳門(mén)"};
ArrayAdapter<String> adapter=new ArrayAdapter<String>(this, 

android.R.layout.simple_spinner_dropdown_item, city);

package fry;

import com.example.SpinnerDemo.R;

import android.app.Activity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.Spinner;

public class Activity01 extends Activity{
  private Spinner spinner1;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity01);
    
    spinner1=(Spinner) findViewById(R.id.spinner1);
    
    initSpinner1();
  }
  public void initSpinner1(){
    String[] city=new String[]{"北京","上海","香港","澳門(mén)"};
    ArrayAdapter<String> adapter=new ArrayAdapter<String>(this, android.R.layout.simple_spinner_dropdown_item, city);
    spinner1.setAdapter(adapter);
  }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
   android:orientation="vertical" >
 
  <Spinner 
     android:id="@+id/spinner1"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     />
 
 </LinearLayout>