Microsoft KB Archive/150753

= How to Create a "Windows-type" Incremental Search Box in VFP =

Article ID: 150753

Article Last Modified on 10/15/2003

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APPLIES TO


 * Microsoft Visual FoxPro 3.0 Standard Edition
 * Microsoft Visual FoxPro 3.0b Standard Edition
 * Microsoft Visual FoxPro 6.0 Professional Edition

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This article was previously published under Q150753



SUMMARY
Although the default List Box control has basic incremental search capabilities, the list box must have focus for the function to work. Its functionality differs from the implementation found in other Windows applications, such as the Search option of Help, where the string to be searched for is entered into a text box above a list box that displays the first matching item as each character is entered.

This article describes how to create a technique that allows a list box to searched incrementally, regardless of its RowSource type.



MORE INFORMATION
 Create a new form in Form Designer. In the Data Environment, add Samples\Data\Customer.DBF. In the form, add a text box, and below it, add a list box. Set the list box RowSource Type as 6-Fields, RowSource as Company.  In the InteractiveChange event of the text box, enter the following: LOCAL nIndex, oList     && prevent conflict with other variables oList = thisform.List1  && create object reference to list box

FOR nIndex = 1 TO oList.ListCount  && loop through each item

* compare the item in the list with the string entered IF UPPER( oList.ListItem(nIndex) ) = UPPER( ALLTRIM( this.Value ) ) oList.ListIndex = nIndex  && select this item if matched EXIT              && drop out of loop ENDIF

ENDFOR

oList.Refresh      && update the display to show selected item 

Make corrections by backspacing over the incorrect characters, or by positioning the pointer in front of the character to be edited with the mouse. The list box then displays the item that contains the remaining characters within the text box.

NOTE: Performance is effected by the number of records and the position of the item to be found within the list. Performance is improved by dividing the list into portions and substituting variables in the FOR statement which lowers the number of items to compare the text string with. In this example, the list is divided into quarters: LOCAL cVal, cLen, c1st, c2nd, c3rd, n1st, n2nd, n3rd, nTop, nEnd, ; nMax, oList oList = Thisform.List1 * 1st = 1 to n2nd-1 nMax = oList.ListCount n1st = INT( nMax * .25 ) && 1st quarter n2nd = INT( nMax * .50 ) && 2nd quarter n3rd = INT( nMax * .75 ) && 3rd quarter c1st = UPPER( oList.ListItem[ n1st ] )  && avoids case sensitivity c2nd = UPPER( oList.ListItem[ n2nd ] )  &&   when list contains c3rd = UPPER( oList.ListItem[ n3rd ] )  &&   mixed case entries cVal = ALLTRIM( UPPER( this.Value ) )   && first character caps cLen = LEN( cVal )

DO CASE CASE cVal <= LEFT( c1st, cLen ) nTop = 1 nEnd = n1st CASE cVal <= LEFT( c2nd, cLen ) nTop = n1st + 1 nEnd = n2nd CASE cVal <= LEFT( c3rd, cLen ) nTop = n2nd + 1 nEnd = n3rd OTHERWISE nTop = n3rd + 1 nEnd = nMax ENDCASE

FOR nIndex = nTop TO nEnd  && loop through each item within range IF UPPER( oList.ListItem[ nIndex ] ) = cVal oList.ListIndex = nIndex  && select this item if matched EXIT                 && drop out of loop ENDIF ENDFOR

oList.Refresh              && update the display to show selected item If the list is extensive and requires a large number of divisions, create an array as a property of the form, and assign the character and numeric division boundaries once in the Init event of the form instead of each time in the InteractiveChange event of the form. In the following example, the list is divided into sections:

Create the following two new Form properties: cLimit[9] and nLimit[9]

In the Init event of the form, enter:

LOCAL nDx, nMax oLst = this.List1 && object reference to this form''s list box nMax = oLst.ListCount    && divide into tenths

FOR nDx = 1 TO 9

* assign number at each tenth boundary (used as index into list) this.nLimit[ nDx ] = INT( nMax * ( .10 * nDx ) )

* assign list item found at this position in the list this.cLimit[ nDx ] = UPPER( oLst.ListItem[ this.nLimit[ nDx ] ] )

ENDFOR

In the InteractiveChange event of the text box, enter:

LOCAL cVal, cLen, nTop, nEnd, nIdx, nDex, oLst oLst = thisform.list1 cVal = ALLTRIM( UPPER( this.Value ) ) cLen = LEN( cVal )

* if not found in the sections checked, default to the last section nTop = thisform.nLimit[ 9 ] + 1 && i.e., one past the end of the 9th nEnd = oLst.ListCount           &&    section to the end of the list

IF cVal <= LEFT( thisform.cLimit[ 1 ], cLen ) && compare to 1st element nTop = 1 nEnd = thisform.nLimit[1] ELSE FOR nIdx = 2 TO 9 && loop through the remaining section limits IF cVal <= LEFT( thisform.cLimit[ nIdx ], cLen ) nTop = thisform.nLimit[ nIdx - 1 ] + 1 && previous end plus 1 nEnd = thisform.nLimit[ nIdx ] && limit of current section EXIT     && drop out of loop since section is found ENDIF ENDFOR ENDIF

* the remaining code is the same structure as in the previous example FOR nDex = nTop TO nEnd  && loop through each item with range

IF UPPER( oLst.ListItem[ nDex ] ) = cVal oLst.ListIndex = nDex EXIT ENDIF ENDFOR

oLst.Refresh

Additional query words: VFoxWin

Keywords: KB150753

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