VertScrollBox Detect when bottom reached android and IOS

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.

GridLayout1

VertScrollBox1

How can I achieve this?

1 Answer
1

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

OnViewportPositionChange()

VertScrollBox1

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.

Math.CompareValue()

Alternatively function SameValue(), also in the Math unit

function SameValue()

Math

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