Android PopupMenu弹出菜单的实现

<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=".mainactivity" > 
 
  <button 
    android:id="@+id/button1" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_alignparentleft="true" 
    android:layout_alignparenttop="true" 
    android:layout_marginleft="96dp" 
    android:layout_margintop="111dp" 
    android:onclick="showpopup" 
    android:text="弹出菜单" /> 
 
</relativelayout> 

<menu xmlns:android="http://schemas.android.com/apk/res/android" > 
 
  <item 
    android:id="@+id/open" 
    android:orderincategory="100" 
    android:showasaction="never" 
    android:title="@string/open"/> 
  <item 
    android:id="@+id/close" 
    android:orderincategory="100" 
    android:showasaction="never" 
    android:title="@string/close"/> 
 
</menu> 

package com.example.menu_popupmenu; 
 
import android.os.bundle; 
import android.app.activity; 
import android.view.menu; 
import android.view.view; 
import android.widget.button; 
import android.widget.popupmenu; 
 
public class mainactivity extends activity { 
 
  private button button; 
 
  @override 
  protected void oncreate(bundle savedinstancestate) { 
    super.oncreate(savedinstancestate); 
    setcontentview(r.layout.activity_main); 
  } 
 
  public void showpopup(view view) { 
    popupmenu popupmenu = new popupmenu(mainactivity.this, view); 
    popupmenu.getmenuinflater().inflate(r.menu.main, popupmenu.getmenu()); 
    popupmenu.show(); 
  } 
 
  @override 
  public boolean oncreateoptionsmenu(menu menu) { 
    // inflate the menu; this adds items to the action bar if it is present. 
    getmenuinflater().inflate(r.menu.main, menu); 
    return true; 
  } 
 
}