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popup menu expand/collapse from an icon in Action Bar
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

      <ImageView
          android:id="@+id/my_option"
          android:layout_gravity="left"
          android:src="@drawable/ic_launcher"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_weight="1"
       />
</LinearLayout>

@Override
    protected void onCreate(Bundle arg0) {
    super.onCreate(arg0);

        ActionBar actionBar = getSupportActionBar();
        View actionBarView = getLayoutInflater().inflate(R.layout.action_bar, null);

        actionBar.setCustomView(actionBarView);

        ImageView actionBarImg = (ImageView) actionBarView.findViewById(R.id.my_option);
        actionBarImg.setOnClickListener(new OnClickListener(){

              public void onClick(View view) {
                  //how to pop up a menu which is expand/collapse below the image icon
              }
        });
   }

private PopupWindow mPopupMenu;
private View mMenuLayout;
private boolean isPopupOpened = false;

mMenuLayout = getLayoutInflater().inflate(R.layout.menu_layout, null);
mPopupMenu = new PopupWindow(mMenuLayout, WindowManager.LayoutParams.MATCH_PARENT, WindowManager.LayoutParams.WRAP_CONTENT);

actionBarImg.setOnClickListener(new OnClickListener() {

    public void onClick(View view) {
        if (isPopupOpened)
        {
            mPopupMenu.dismiss();
            isPopupOpened = false;
        }
        else
        {
            mPopupMenu.showAsDropDown(tv);
            isPopupOpened = true;
        }
    }

});