Don't mind people!
I've figured out!
For app designer,
I coded like this!
app.UIFigure.Position(3)
app.h = findobj(app.UIFigure, '-property', 'FontSize');
app.hFontSize = cell2mat(get(app.h,'FontSize'));
position = app.UIFigure.Position;
widthF = position(3);
newFontSize = double(widthF) * app.hFontSize / 1463.0;
set(app.h,{'FontSize'}, num2cell(newFontSize));