Use this simply.
Spinner spinner = (Spinner) findViewById(R.id.spinner); try { Field popup = Spinner.class.getDeclaredField("mPopup"); popup.setAccessible(true);
// Get private mPopup member variable and try cast to ListPopupWindow android.widget.ListPopupWindow popupWindow = (android.widget.ListPopupWindow) popup.get(spinner);
// Set popupWindow height to 500px popupWindow.setHeight(500); } catch (NoClassDefFoundError | ClassCastException | NoSuchFieldException | IllegalAccessException e) { // silently fail... }

You can use Reflection.
Spinner spinner = (Spinner) findViewById(R.id.spinner); try { Field popup = Spinner.class.getDeclaredField("mPopup"); popup.setAccessible(true); // Get private mPopup member variable and try cast to ListPopupWindow android.widget.ListPopupWindow popupWindow = (android.widget.ListPopupWindow) popup.get(spinner); // Set popupWindow height to 500px popupWindow.setHeight(500); } catch (NoClassDefFoundError | ClassCastException | NoSuchFieldException | IllegalAccessException e) { // silently fail... }