Kbase P110148: How to clear a combo-box widget?
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
10/25/2005 |
|
Status: Unverified
GOAL:
How to clear a combo-box widget?
GOAL:
How to display a blank in a native drop-down-list combo-box defined as list-items or list-item-pairs?
GOAL:
How to reset what is currently being displayed in the box of a drop-down-list back to blank value?
FACT(s) (Environment):
Progress 8.x
Progress 9.x
OpenEdge 10.x
FIX:
The following code demonstrates how to display a blank in a native drop-down-list combo-box defined as list-items (or list-item-pairs in Progress 9.x or later). Developers might want to be able to clear a combo-box without including a blank item in the drop-down-list. This would appear to be possible since running a window containing combo-boxes with no initial values, renders them blank. Some developers have used the method:
MyCombo:LIST-ITEMS = MyCombo:LIST-ITEMS.
which does clear the combo-box but is slow. When there are many items in the list, this method consumes close to 100% CPU for a some time; an approach particularly unsatisfactory from a performance standpoint.
A better method is to apply the following:
MyCombo:ADD-FIRST(" "). /*ADD-FIRST(" "," ") for list-item-pairs*/
MyCombo:SCREEN-VALUE = " ".
MyCombo:DELETE(1).
Or you may even define your own method with the following UDF for reusability:
FUNCTION ClearCombo RETURNS CHARACTER ( h AS HANDLE ) :
h:ADD-FIRST(" "). /*ADD-FIRST(" "," ") for list-item-pairs*/
h:SCREEN-VALUE = " ".
h:DELETE(1).
END FUNCTION.
ClearCombo(MyCombo:HANDLE).