@Override 
public boolean onCreateOptionsMenu(Menu menu){ 
  MenuInflater inflater = getMenuInflater(); 
  inflater.inflate(R.menu.main, menu); 
  return true; 
} 

<menu xmlns:android="http://schemas.android.com/apk/res/android" > 
  <item 
    android:id="@+id/action_cart" 
    android:title="扫描" 
    android:orderInCategory="100" 
    android:showAsAction="always"/> 
</menu> 

@Override  
public boolean onOptionsItemSelected(MenuItem item){ 
  switch (item.getItemId()) { 
  case R.id.action_cart://监听菜单按钮 
     
    break; 
  } 
  return super.onOptionsItemSelected(item); 
}