VertScrollBox Detect when bottom reached android and IOS

Question

I have GridLayout1 on a VertScrollBox1. The vertical scroll box scrolls through the content of the grid layout. I need to detect when the Vertical scroll box reach the bottom so I get to load more content to the grid layout. And do it again whenever bottom is reached again.

How can I achieve this?

Answer 1

Use the OnViewportPositionChange() of the VertScrollBox1. Then some simple arithmetics tell you when you are at the bottom:

uses Math, ...;
// ...

procedure TForm1.VertScrollBox1ViewportPositionChange(Sender: TObject;
  const OldViewportPosition, NewViewportPosition: TPointF;
  const ContentSizeChanged: Boolean);
begin
  if CompareValue(NewViewportPosition.Y, GridLayout1.Height - VertScrollBox1.Height) = EqualsValue then
    Memo1.Lines.Add('At bottom, time to grow and load more content to the GridLayout');
end;

Since the values we compare are floats, use Math.CompareValue() for comparison.

Alternatively function SameValue(), also in the Math unit