<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=".Main" >

 <Spinner
  android:id="@+id/spinner"
  android:layout_width="300sp"
  android:layout_height="50sp"
  android:layout_gravity="center_horizontal" />

</LinearLayout>

package com.app.main;

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

public class Main extends Activity {

 Spinner spinner = null;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);

  spinner = (Spinner) this.findViewById(R.id.spinner);
  ArrayAdapter adapter = new ArrayAdapter(this,
    android.R.layout.simple_spinner_item, new String[] { "第一项",
      "第二项", "第三项" });

  //设置下拉样式
  adapter.setDropDownViewResource(android.R.layout.simple_dropdown_item_1line);
  spinner.setAdapter(adapter);
 }

}

<TextView xmlns:android="http://schemas.android.com/apk/res/android" 
 android:id="@android:id/text1"
 style="?android:attr/spinnerItemStyle"
 android:singleLine="true"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:ellipsize="marquee"
 android:textAlignment="inherit"/>

<TextView xmlns:android="http://schemas.android.com/apk/res/android" 
 android:id="@android:id/text1"
 style="?android:attr/dropDownItemStyle"
 android:textAppearance="?android:attr/textAppearanceLargePopupMenu"
 android:singleLine="true"
 android:layout_width="match_parent"
 android:layout_height="?android:attr/listPreferredItemHeight"
 android:ellipsize="marquee" />