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; 
  } 
 
}