问如何创建像PopupWindow showAsDropDown这样的动画？

EN

public void showPopUp(final View view) {


    PopupMenu popup = new PopupMenu(this, view);
    MenuInflater inflater = popup.getMenuInflater();

    //Note that R.menu.option is a menu in the menu.xml
    inflater.inflate(R.menu.options, popup.getMenu());

    /* Force icons to show if you want to display icons
    Object menuHelper = null;
    Class[] argTypes;
    try {
        Field fMenuHelper = PopupMenu.class.getDeclaredField("mPopup");
        fMenuHelper.setAccessible(true);
        menuHelper = fMenuHelper.get(popup);
        argTypes = new Class[] { boolean.class };
        menuHelper.getClass().getDeclaredMethod("setForceShowIcon", argTypes).invoke(menuHelper, true);
    } catch (Exception e) {
        popup.show();
        return;
    }
    */
    popup.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
        @Override
        public boolean onMenuItemClick(MenuItem item) {
            switch (item.getItemId()) {
                case R.id.item1:
                    // do thing when item1 clicked
                    break;

                case R.id.item2:

                    // do thing when item2 licked                        break;

                default:
                    return false;
            }
            return false;
        }
    });

    popup.show();


} 

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android" >

<item
    android:id="@+id/item1"
    android:showAsAction="ifRoom|withText"
    android:title="item1"
    android:visible="true"/>

<item
    android:id="@+id/item2"
    android:showAsAction="ifRoom|withText"
    android:title="item2"
    android:visible="true"/>

</menu>