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Custom Layout manager scrollPositionChanged() method

/ Published in: ActionScript 3
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  1. override protected function scrollPositionChanged():void {
  2. 	if (!useVirtualLayout) {
  3. 		super.scrollPositionChanged();
  4. 		return;
  5. 	}
  6.  
  7. 	var g:GroupBase = target;
  8. 	if (!g)
  9. 		return;     
  10. 	updateScrollRect(g.width, g.height);
  11.  
  12. 	var n:int = g.numElements - 1;
  13. 	if (n < 0) {
  14. 		setIndexInView(-1, -1);
  15. 		return;
  16. 	}
  17.  
  18. 	var scrollR:Rectangle = getScrollRect();
  19. 	if (!scrollR) {
  20. 		setIndexInView(0, n);
  21. 		return;    
  22. 	}
  23.  
  24. 	var y0:Number = scrollR.top;
  25. 	var y1:Number = scrollR.bottom - .0001;
  26. 	if (y1 <= y0) {
  27. 		setIndexInView(0, n);
  28. 		return;
  29. 	}
  30.  
  31. 	var i0:int, i1:int;
  32. 	if (y0 < 0) {
  33. 		i0 = 0;
  34. 		i1 = yToIndex.length - 1 > g.height ? yToIndex[g.height + 1]  : g.numElements - 1;
  35. 		setIndexInView(i0, i1);
  36. 		return;	
  37. 	}
  38.  
  39. 	if (y1 < yToIndex.length - 1) {
  40. 		i0 = yToIndex[Math.floor(y0)];
  41. 		i1 = yToIndex[Math.ceil(y1)];
  42. 	} else {
  43. 		if (yToIndex.length - 1 - g.height < 0)
  44. 			i0 = 0;
  45. 		else
  46. 			i0 = yToIndex[yToIndex.length - 1 - g.height];
  47. 		i1 = yToIndex[yToIndex.length - 1];
  48. 	}
  49.  
  50. 	setIndexInView(i0, i1);
  51. 	//invalidate display list only if we have items that are not already renderered
  52. 	if (i0 < currentFirstIndex || i1 > currentLastIndex) {
  53. 		g.invalidateDisplayList();
  54. 	}
  55. }

URL: http://corlan.org/?p=2987

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