Question

Since Android has different size of layout, the number of rows can be shown in the ListView is therefore variable, ideally, we need to perform API call like..

http://www.example.com/get_product?count=N&..

Where N = number of rows can be displayed in a given ListView + 10 items buffer for offscreen scrolling effect.

What would be best method to define the value of N in the app?

Answer 1

Try this:

ListView list = (ListView) findViewById(R.id.list) //R.id.list will be your listview id in the layout    
int n = Double.intValue(list.getHeight()/list.getChildAt(1).getHeight())

If it doesn’t work because it need to first create the list to get a child, and you have the dp height of the listItem (could be if you use a custom layout), you could use

ListView list = (ListView) findViewById(R.id.list) //R.id.list will be your listview id in the layout    
Resources r = getResources();
int px = Math.round(TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, !!!YOUR LISTITEM HEIGHT IN DP!!!, r.getDisplayMetrics())); //Convert DP to actual size in pixels (rounded)
int n = Double.intValue(list.getHeight()/px)