1001 Things You Wanted To Know About Visual FoxPro phần 3 pot

92 1001 Things You Always Wanted to Know About Visual FoxPro

.Value = EVAL( .cAlias + '.' + .cField )

ENDIF

ELSE

*** Otherwise, save the current work area

*** before switching to the specified table

lnSelect = SELECT()

SELECT ( .cAlias )

*** And locate the specified record

LOCATE FOR UPPER( ALLTRIM( EVAL (.cField ) ) ) = UPPER( lcSoFar )

IF FOUND()

.Value = EVAL( .cAlias + '.' + .cField )

ENDIF

*** Restore the original work area

SELECT ( lnSelect )

ENDIF

ENDIF

At this point we have either found the desired record in cAlias or we are at the end of the

file. All that remains to be done is to reset the highlighted portion of the text box correctly and

refresh the controls in the parent container (if this was specified by setting .lRefreshParent =

.T.):

*** If we need to refresh the parent container do it here

IF .lRefreshParent

.RefreshParent()

ENDIF

*** Highlight the portion of the value after the insertion point

.SelStart = lnSelStart

lnSelLength = LEN( .Value ) - lnSelStart

IF lnSelLength > 0

.SelLength = lnSelLength

ENDIF

*** If we have refreshed the controls in the parent container,

*** there are timing issues to overcome

*** Even though .SelStart and .SelLength have the correct values,

*** the search box does not appear highlighted correctly without this delay

=INKEY( .1, 'H' )

ENDWITH

Notice the INKEY() command here, and take some time to read the comment above if you

haven't already. This problem is not specific to our incremental search text box and timing

issues like this are not uncommon in Visual FoxPro. (We have also run into it when displaying

multi-select list boxes in which the previous selections are highlighted. In that case, using

INKEY() in the form's refresh allows the list box to be highlighted correctly.) It is interesting to

note that the INKEY() command is not required in the code above when lRefreshParent = .F.

This lends support to the assumption that this is nothing more than a timing issue. The short

pause allows Visual FoxPro to catch up.

Numeric text box (Example: CH04.VCX::txtNum and txtNumeric)

Visual FoxPro has inherited some serious shortcomings with respect to entering numeric data

from its FoxPro ancestors. It's not too bad when the entire field is selected, and the number is

not formatted with separators. However, problems begin to occur when the insertion point is

Chapter 4: Basic Controls 93

not at the beginning of the displayed value. Sometimes the user is trying to type the number 10,

but all he can type is 1 and, with confirm set off, the value of the text box becomes 1 and the

cursor moves on to the next field. We have also seen the opposite problem. The user wants to

enter 3 but after typing 3 and exiting the control, the number 30 is displayed instead of the

intended 3. So what can a Visual FoxPro developer do to help?

There are a few workarounds to this problem. You could create a numeric text box to

select the entire field and remove any separators used to format the number. This code in the

text box's GotFocus method allows the number to be entered correctly:

WITH This

*** Save the input mask

.cOldInputMask = .InputMask

*** Remove separators from input mask

.InputMask = STRTRAN( .cOldInputMask, ',', '' )

*** Perform Visual FoxPro native GotFocus()

TextBox::GotFocus()

*** Select the entire field

.SelStart = 0

.SelLength = LEN( .cOldInputMask )

*** Don't let base class behavior reset SelStart/SelLength

NODEFAULT

ENDWITH

Since we need to change the text box's inputMask to accomplish this, we add a custom

property called cOldInputMask to hold the original inputMask assigned to the control. We will

need this property in the text box's LostFocus method in order to restore the formatting like so:

This.InputMask = This.cOldInputMask

Of course, we already have a text box class that correctly selects the entire field where you

tab into it or mouse-click on it. Our base class text box does this when SelectOnEntry = .T. So

all we have to do is base our numeric text box on our base class text box, set SelectOnEntry to

true, and put this code in its GotFocus method:

WITH This

*** Save the original input mask

.cOldInputMask = .InputMask

*** Remove separators from input mask

.InputMask = STRTRAN( .cOldInputMask, ',', '' )

*** Perform the parent class behavior

DODEFAULT()

ENDWITH

The numeric text box described above may be sufficient for you. It's easy to create, doesn't

contain a lot of code and works around the problems involved in entering numeric data

correctly. But wouldn't it be nicer to have a numeric text box that does calculator style entry

from right to left? We have seen several examples of such text boxes and, in our opinion, they

all suffer from the same shortcoming. Either the cursor can be seen flashing to the left as

characters appear from the right or there is no cursor at all. Both of these solutions tend to

make things confusing for the user. So we set out to create the ultimate Visual FoxPro numeric

94 1001 Things You Always Wanted to Know About Visual FoxPro

text box. And we very quickly discovered why none currently exists. It was HARD! So we

hope you find this useful as it is the result of entirely too many hours and too much blood,

sweat, and tears. Not only does it do calculator style entry, the cursor is also positioned on the

correct character. When the value in the text box is not selected, you can even delete or insert

individual digits in the middle of the number displayed in the text box.

The numeric text box is a simple control to use. Just drop it on a form, page or container

and set its ControlSource property. That's all! You don't even need to set its InputMask unless

you want the control to be unbound because it is capable of formatting itself when bound. The

way most numeric text boxes work is by changing the value into a character string,

manipulating the string and the InputMask and then re-converting the string to a numeric value.

However, our numeric text box is actually an unbound control (even though you can set it up

as if it were bound) and works because its value actually is a character string and is

manipulated as such. It uses custom code to update its ControlSource with the numeric

equivalent of the character string which is its value.

This example is designed to work either unbound or bound to a field in a table, cursor or

view. If you need to bind to a form property, the code will need a little modification to account

for it. An example of how to do this can be found in the UpdateControlSource method of the

spnTime class described later in this chapter.

The following, eight custom properties were added to our custom numeric text box. They

are all used internally by the control and you do not need to do anything with them explicitly.

Table 4.2 Custom properties of the numeric text box

Property Description

CcontrolSource Saves the controlSource if this is a bound control before it is unbound in the Init

method

Cfield Field name portion of ControlSource if it is bound

CinputMask Stores original inputMask when it is specified, otherwise stores the inputMask

constructed by the control

ColdConfirm Original setting of SET( 'CONFIRM' ) saved in GotFocus so it can be restored in

LostFocus.

ColdBell Original setting of SET('BELL') saved in GotFocus so it can be restored in

LostFocus

Cpoint Character returned by SET( 'POINT' )

Cseparator Character returned by SET( 'SEPARATOR' )

Ctable Table name portion of ControlSource if it is bound

LchangingFocus Flag set to suppress KEYBOARD '{END}' which is used to position the cursor at

the rightmost position in the text box. If we do this when the control is losing focus,

it messes up the tab order

NmaxVal Maximum value allowed in the control

The SetUp method, called by the TextBox's Init method, saves the content of the

ControlSource property to the custom cControlSource property before unbinding the control

from its ControlSource. It also determines, and sets up, the InputMask for the control. Even

though this code is executed only once when the text box is instantiated, we have put it in a

custom method to avoid coding explicitly in events whenever possible. Notice that we use