Q166378: HOWTO: Simulate an Incremental Search from a Text Box
Article: Q166378
Product(s): Microsoft FoxPro
Version(s):
Operating System(s):
Keyword(s): kbDesigner kbOOP kbvfp500 kbvfp600
Last Modified: 06-AUG-1999
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The information in this article applies to:
- Microsoft Visual FoxPro for Windows, versions 5.0, 5.0a, 6.0
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SUMMARY
=======
The combo box control has an Incremental Search property that, when set to true
(.T.), searches the Control Source of the combo box with each keystroke. Thus,
if a user types the string "ABC," the table is searched after each keystroke,
first for the letter "A," then the string "AB," then the string "ABC."
While this is a very useful property, the fact that the search is triggered by
action rather than inaction causes UI problems--the user may not want to search
for each letter of a string as he or she builds it, but rather search for the
whole string after it has been fully entered. The text box does not have an
incremental search property, but the action can be simulated, and made to search
when the user stops typing, rather than when the user is entering the string for
which to search.
The code in this article creates a fully editable text box that implements an
incremental search procedure. Using a timer, the incremental search is triggered
when the user has not pressed a key for a certain timeout period.
MORE INFORMATION
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1. Create a new form, and add the Customer table from the Testdata database
(located in the Samples folder in Visual FoxPro 5.0 and the Microsoft Visual
Studio\Common\Samples\Data folder in Visual FoxPro 6.0) to the
DataEnvironment. Drag the table onto the form to create a grid. Make sure the
grid is named Grid1. Add to the form three custom properties: PREVAL,
TICKCOUNT, and HOLDVALUE. Change the default values of PREVAL and HOLDVALUE
to blank. Change the default value of TICKCOUNT to 0.
2. Add to the form a custom method named SearchVal. To that method, add the
following code:
* Only seek if the value in the text box has changed
IF !(THIS.PREVAL == ALLTRIM(THIS.TEXT1.VALUE))
* Set the previous value to the current value
THIS.PREVAL = ALLTRIM(THIS.TEXT1.VALUE)
* Seek for the text value
GO TOP
SEEK THIS.PREVAL
IF FOUND()
* The custom property holdvalue is used to store the
* string the user has entered.
THISFORM.HOLDVALUE = THIS.PREVAL
* This sets focus to the grid so that the located
* record is displayed in the grid and the
* RecordMark is turned on for the located record
THISFORM.GRID1.SETFOCUS
* Reset focus immediately to the text box
THIS.TEXT1.SETFOCUS
THIS.TEXT1.VALUE = THISFORM.HOLDVALUE
THIS.TEXT1.SELSTART = LEN(THISFORM.HOLDVALUE)
ENDIF
ENDIF
3. Add a timer to the form, and set the Interval property of the timer to 50. In
the Timer event of the Timer control, add the following code:
THIS.PARENT.TICKCOUNT = THIS.PARENT.TICKCOUNT + 1
IF THIS.PARENT.TICKCOUNT >= 20
THIS.PARENT.TICKCOUNT = 0
THIS.PARENT.SEARCHVAL()
ENDIF
4. Add a text box to the form. Do not specify a control source for the text box.
In the Load event of the form, enter the following command:
SET ORDER TO CUST_ID && or whatever the name of the index tag
&& for the cust_id field is.
5. Add the following code to the text box KeyPress event procedure:
* NOTE: The SHIFT-DIRECTIONKEY highlighting works, but is non
* standard. For example, SHIFT-LEFT-ARROW highlighting three
* characters to the right, then hitting the right arrow key, only
* increments the current position by one. In most editors, doing
* this would increment the current position by four. In order to
* emulate this behavior, however, it would be necessary to save
* the last key pressed in a variable, then check it to find out
* in which direction we were last moving, then perform a
* calculation ... it just didn't seem worth the effort.
LOCAL nPos, nLen, nSel
nPos = THIS.SELSTART && current pos of the cursor
nLen = LEN(ALLTRIM(THIS.VALUE)) && length of text in textbox
nSel = THIS.SELLENGTH && number of selected chars
THIS.PARENT.TICKCOUNT = 0
* Turn off all default processing of the Keypress Event;
* this is necessary for code to work
NODEFAULT
DO CASE
* Tests/traps for nKeycode >= 65, <= 122 (limits input to
* alpha characters), nKeycode = 32 (allows for spaces). To
* allow for input of numerals and/or other characters,
* refer to the INKEY() topic in the Help file for codes
* 39 is for single quote
CASE (nKeyCode >= 65 AND nKeyCode <= 122) OR nKeyCode = 32;
OR nKeyCode = 44 OR nKeyCode = 45 OR nKeyCode = 39
* Insert the new character in the right place
THIS.VALUE = UPPER(LEFT(THIS.VALUE, nPos) + ;
CHR(nKeyCode) + RIGHT(THIS.VALUE,;
nLen - (nPos + nSel)))
* Increment our position holder so we are placed
* after the new letter
nPos = nPos + 1
nSel = 0
* Tests/traps for the SHIFT-LEFT-ARROW combo (highlight-left)
CASE nKeyCode = 52
* Move one to the left, increase number selected by one
IF nPos > 0
nPos = nPos - 1
nSel = nSel + 1
ENDIF
* Tests/traps for the SHIFT-RIGHT-ARROW combo (highlight-right)
CASE nKeyCode = 54
* Increase number selected by one, if there is more to
* select
IF (nPos + nSel) < nLen
nSel = nSel + 1
ENDIF
* Tests/traps for the SHIFT-HOME combo (highlight-left-end)
CASE nKeyCode = 55
* Set the number of characters selected to the number of
* characters between our current position and the start
* position, then move to the start position
nSel = nSel + nPos
nPos = 0
* Tests/traps for the SHIFT-END combo (higlight-right-end)
CASE nKeyCode = 49
* Set the number of characters selected to the number to
* the right of our current position
nSel = nLen - nPos
* Tests/traps for the LEFT-ARROW key
CASE nKeyCode = 19
* Deselect any selected characters
nSel = 0
* Move left one
IF nPos > 0
nPos = nPos - 1
ENDIF
* Tests/traps for the RIGHT-ARROW key
CASE nKeyCode = 4
* Deselect any selected characters
nSel = 0
* Move right one
IF nPos < nLen
nPos = nPos + 1
ENDIF
* Tests/traps for the HOME key
CASE nKeyCode = 1
* Deselect any selected characters
nSel = 0
* Move to the start
nPos = 0
* Tests/traps for the END key
CASE nKeyCode = 6
* Deselect any selected characters
nSel = 0
* Move to the end
nPos = nLen
* Tests/traps for the DELETE key
CASE nKeyCode = 7
* If we have not 'highlighted' the letter we want to delete,
* the count of letters to delete will be zero, so we have
* to manually set the letter to remove
IF nSel = 0
nSel = 1
ENDIF
* Rebuild the string without the deleted character(s)
THIS.VALUE = LEFT(THIS.VALUE, nPos) + ;
RIGHT(THIS.VALUE, nLen - (nPos + nSel))
* Deselect any selected characters
nSel = 0
* Tests/traps for the BACKSPACE key
CASE nKeycode = 127
* If no letters are 'highlighted', just delete the one
* before the cursor and
* move the cursor back one
IF nSel = 0
IF nPos > 0
THIS.VALUE = LEFT(THIS.VALUE, nPos - 1) + ;
RIGHT(THIS.VALUE, nLen - nPos)
nPos = nPos - 1
ENDIF
* If letters are highlighted, remove the block of
* highlighted letters, and don't move the cursor
* (just like hitting DELETE)
ELSE
THIS.VALUE = LEFT(THIS.VALUE, nPos) + ;
RIGHT(THIS.VALUE, nLen - (nPos + nSel))
ENDIF
* Deselect any selected characters
nSel = 0
ENDCASE
* Get rid of whitespace at the end of the entered word
IF nLen != LEN(ALLTRIM(THIS.VALUE))
THIS.MAXLENGTH = LEN(ALLTRIM(THIS.VALUE)) + 1
ENDIF
* This moves the cursor to the current position in the string in the
* text box
THIS.SELSTART = nPos
* And this selects the proper number of characters
THIS.SELLENGTH = nSel
6. Save and run the form. Type a search field into the text box. After a brief
pause, any matching fields should be located within the database and pointed
to on the Grid. Experiment with different timeout periods until you find one
with which you are comfortable.
General Notes
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- In this example it is assumed that the text box is named Text1. If the name
of that text box is different, modify the code accordingly.
- The NODEFAULT command turns off all of the default processing of the KeyPress
event and allows the code to completely control the processing of the key
presses. This command is necessary.
- As is noted in a few of the comments, the edit emulation is not perfect, but
it is fairly close to target.
(c) Microsoft Corporation 1997, All Rights Reserved. Contributions by Robert
Mobbs, Microsoft Corporation.
Additional query words:
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Keywords : kbDesigner kbOOP kbvfp500 kbvfp600
Technology : kbVFPsearch kbAudDeveloper kbVFP500 kbVFP600 kbVFP500a
Issue type : kbhowto
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