Vai Manh ve TextBox & ListBox

K 7	*Nhng cu hi v*
	VISUALBASIC Xem bai viet bang font Unicode

	thdang@tlnet.com.vn

Trong k ny:

1. Kim tra vic nhp liu vo TextBox
2. Chuyn i k t trong cc i tng c kh nng hiu chnh (Editbox) thnh ch hoa
3. B qua mt s k t khi g vn bn trong TextBox
4. Xa cc mc chn (Item) trong Combo/List Box
5. Lm sao  tt tnh nng Wordwrap ca Rich TextBox
6. Thm mt dng mi vo cui TextBox ang cha vn bn
7. Lm sao  Shut down hay Reboot li Windows ?
8. Lm cho TEXTBOX tr thnh read only hoc cm ngi dng thay i ni dung
9. M file vi chng trnh lin kt (associated program)
10. Lm sao  play cc file: MID, WAV, AVI ?

1. Kim tra vic nhp liu vo TextBox

1. Kim tra vic nhp liu vo TextBox
2. Chuyn i k t trong cc i tng c kh nng hiu chnh (Editbox) thnh ch hoa
3. B qua mt s k t khi g vn bn trong TextBox
4. Xa cc mc chn (Item) trong Combo/List Box
5. Lm sao  tt tnh nng Wordwrap ca Rich TextBox
6. Thm mt dng mi vo cui TextBox ang cha vn bn
7. Lm sao  Shut down hay Reboot li Windows ?
8. Lm cho TEXTBOX tr thnh read only hoc cm ngi dng thay i ni dung
9. M file vi chng trnh lin kt (associated program)
10. Lm sao  play cc file: MID, WAV ?

Trong chng trnh nu bn c yu cu bt ngi dng phi nhp liu vo mi TextBox ang hin hu trn mt form  thc hin mt vic no , song khng phi ai cng "vng li". bn cn kim tra xem ngi dng c nhp y  thng tin vo cc TextBox cha.   nhc cng phi kim tra tng ci mt (thng kim tra khi c s kin LostFocus), vi hm ny bn ch vic chuyn cho n mt tham s l Form cha cc TextBox cn kim tra, n c nhim v truy tm nhng TextBox cn trng v phi by ra mn hnh bng bng mt biu hin khc thng no .

Hm ny nhn vo mt i s duy nht l Form (thng l form hin hnh "Me"), sau  n s tm n tt c cc Textbox c trn form bng cch s dng cu lnh "For Each Control" nu c Textbox cn trng th i mu nn BackColor (mu hng), ng thi tr v mt gi tr kiu Boolean l True. Khng nhng l TextBox, nu l ComboBox vn b vng lp ny chiu c.

 th hm ny bn hy to mt form, to vi chc ci TextBox (tn chi cng c) v mt CommandButton (name: cmdTextEmpty). G vo on Code sau:

Private Sub cmdTestEmpty_Click()

If IsEmpty(Me) Then

MsgBox "Some textboxes are still empty"

End If

End Sub

Function IsEmpty(Frm As Form) As Boolean

Dim tmpControl As Control

On Error Resume Next

IsEmpty = False

For Each tmpControl In Frm.Controls

If Trim(tmpControl.Text) = "" Then

If Err.Number = 0 Then

IsEmpty = True

tmpControl.BackColor = &HFFC0FF 'Mu hng

End If

Err.Clear

Else

If tmpControl.BackColor = &HFFC0FF Then

tmpControl.BackColor = QBColor(15)'Mu trng

End If

Next tmpControl

End Function

Nhn F5  chy chng trnh. By gi bn hy lm cho mt TextBox trng (vi ci cng c), sau  click vo CommandButton, bn s thy cc TextBox trng b i mu thnh mu hng. Hy g vn bn vo cc TextBox mu hng , sau  click ln CommandButton ln na, by gi th m ri, cc TextBox  tr li bnh thng (nn trng).

2. Chuyn i k t trong cc i tng c kh nng hiu chnh (Editbox) thnh ch hoa

1. Kim tra vic nhp liu vo TextBox
2. Chuyn i k t trong cc i tng c kh nng hiu chnh (Editbox) thnh ch hoa
3. B qua mt s k t khi g vn bn trong TextBox
4. Xa cc mc chn (Item) trong Combo/List Box
5. Lm sao  tt tnh nng Wordwrap ca Rich TextBox
6. Thm mt dng mi vo cui TextBox ang cha vn bn
7. Lm sao  Shut down hay Reboot li Windows ?
8. Lm cho TEXTBOX tr thnh read only hoc cm ngi dng thay i ni dung
9. M file vi chng trnh lin kt (associated program)
10. Lm sao  play cc file: MID, WAV ?

Cc i tng loi ny gm c TextBox, Combobox. Sau y l cc on code dng  chuyn i vn bn hin hu trong cc Control thnh ch hoa. Dng cho mt s i tng:

+ Cho combobox khng c drop down

Dim hwndListbox As Integer
Dim childhWnd As Integer

hwndListbox = GetWindow(cbo1.hWnd, GW_CHILD)

childhWnd = GetWindow(hwndListbox, GW_HWNDNEXT)

lStyle = GetWindowLong(childhWnd, GWL_STYLE)

lStyle = lStyle Or ES_UPPERCASE

lRes = SetWindowLong(childhWnd, GWL_STYLE, lStyle)

+ Cho ComboBox c drop down

childhWnd = GetWindow(cbo1.hWnd, gw_child)

lStyle = GetWindowLong(childhWnd, GWL_STYLE)

lStyle = lStyle Or ES_UPPERCASE

lRes = SetWindowLong(childhWnd, GWL_STYLE, lStyle)

+ Cho TextBox

lStyle = GetWindowLong(Txt1.hWnd, GWL_STYLE)

lStyle = lStyle Or ES_UPPERCASE

lRes = SetWindowLong(Txt1.hWnd, GWL_STYLE, lStyle)

3. B qua mt s k t khi g vn bn trong TextBox

Nu bn cn loi b mt s k t khi ngi dng g vn bn vo trong mt Textbox, thng l cc k t c bit nh: "!@#$%^&*()_+-=" . Sau y l mt gii php. Bng cch dng lin tc hm InStr mi khi c phm g (S kin KeyPress)

Private Sub Text1_KeyPress(KeyAscii As Integer)

Dim sTemplate As String

sTemplate = "!@#$%^&*()_+-="

If InStr(1, sTemplate, Chr(KeyAscii)) > 0 Then

KeyAscii = 0

End If

End Sub

4. Xa cc mc chn (Item) trong Combo/List Box

 xa cc Item trong Combo box hay List box, bn cn phi duyt ngc, tc l t (ListCout-1) n 0. Sau y l mt th d minh ha. Bng cch dng vng lp For, km theo Step -1  duyt ngc.

Sub cmdDeleteItems_Click ()

Dim i As Integer

For i = List1.ListCount - 1 To 0 Step -1

If List1.Selected(i) Then

List1.RemoveItem i

End If

Next i

End Sub

5. Lm sao  tt tnh nng Wordwrap ca Rich TextBox

C ln no bn bc mnh v khng tm c thuc tnh no  tt kh nng Wordwrap ca RichTextBox khng ? Tc l khng cho n t ct dng vn bn ca mnh mi khi chm cnh phi. Tm cng khng c, chc Bill qun to ri chng?

Khng hiu ti sao khi sng tc ra RichTextBox, Bill khng chu lm lun cho n chc nng Wordwrap  cho b con c th On/Off khi cn ? Khng bit l Bill c  hay "l qun" khng to !?

Tht ra m ni RichTextBox khng c tnh nng Wordwrap  d dng s dng trn Internet y m. Nhng suy cho cng chng ta c th nhanh chng gii ta hn ch ny bng cch gn cho thuc tnh RightMargin ca RichTextBox mt con s thit "b", i chao ng qu khim tn vi s 0 na ! Mt con s chng 100.000 cng c m, lc  th kh nng Worwrap ca n b y i tut lut  mt ni cch mn hnh ca bn gn 400m v pha phi. Vi mnh ny bn ch tht s i bi khi c dng vn bn di hn c  thi.

Bn cng ng qun cho hin th ScrollBar  ngi dng d dng trong vic xem cc dng vn bn "c  di" ca bn.

6. Thm mt dng mi vo cui TextBox ang cha vn bn

Nu bn c nhu cu thm ngy thng vo cui mt vn bn sau khi hiu chnh,  bit r c ngy cp nht cui cng ca mt ti liu no  (thng gp trong cc chng trnh lm s tay, nht k... ).  lm vic ny bn hy vn dng cc Properties: SelStart, SelText ca TextBox.

Sau y l on code thm ngy thng vo cui vn bn trong TextBox

Dim strNewText As String

With Text1

strNewText = "Updated: " & Date

.SelStart = Len(.Text)

.SelText = vbNewLine & strNewText

End With

7. Lm sao  Shut down hay Reboot li Windows ?

1. Kim tra vic nhp liu vo TextBox
2. Chuyn i k t trong cc i tng c kh nng hiu chnh (Editbox) thnh ch hoa
3. B qua mt s k t khi g vn bn trong TextBox
4. Xa cc mc chn (Item) trong Combo/List Box
5. Lm sao  tt tnh nng Wordwrap ca Rich TextBox
6. Thm mt dng mi vo cui TextBox ang cha vn bn
7. Lm sao  Shut down hay Reboot li Windows ?
8. Lm cho TEXTBOX tr thnh read only hoc cm ngi dng thay i ni dung
9. M file vi chng trnh lin kt (associated program)
10. Lm sao  play cc file: MID, WAV ?

Trong Visual Basic 32bit. Khai bo hm API nh sau:

Declare Function ExitWindowsEx Lib "user32" (ByVal uFlags As Long, ByVal dwReserved As Long) As Boolean

Public Const EWX_SHUTDOWN = 1

Khi s dng bn ch vic:

Dim success

success = ExitWindowsEx(EWX_SHUTDOWN, 0)

Nu thnh cng, hm ny s tr v True.

+ EWX_REBOOT = 2 s lm cho Windows 9.x Reboot

+ EWX_LOGOFF = 0  Log off.

Vi phin bn 16bit

Declare Function ExitWindows Lib "user" (ByVal wReturnCode as Long,ByVal dwReserved as Integer) as Integer

Exit Windows:

RetVal% = ExitWindows(0, 0)

Exit & restart Windows:

RetVal% = ExitWindows(&H42, 0)

Exit Windows & restart the system:

RetVal% = ExitWindows(&H43, 0)

8. Lm cho TEXTBOX tr thnh read only (cm ngi dng thay i ni dung)

1. Kim tra vic nhp liu vo TextBox
2. Chuyn i k t trong cc i tng c kh nng hiu chnh (Editbox) thnh ch hoa
3. B qua mt s k t khi g vn bn trong TextBox
4. Xa cc mc chn (Item) trong Combo/List Box
5. Lm sao  tt tnh nng Wordwrap ca Rich TextBox
6. Thm mt dng mi vo cui TextBox ang cha vn bn
7. Lm sao  Shut down hay Reboot li Windows ?
8. Lm cho TEXTBOX tr thnh read only hoc cm ngi dng thay i ni dung
9. M file vi chng trnh lin kt (associated program)
10. Lm sao  play cc file: MID, WAV ?

Nu bn s dng Visual Basic 5.0 tr ln th c thuc tnh Locked, nu gn l True th ngi dng khng th thay i ni dung ca TextBox (Read Only).

C mt s  kin cho rng, bn cn chp ly s kin KeyPress v KeyDown lm cho chng thnh zero. Tuy nhin, gii php tt nht vn l hm Windows API SendMessage.

Global Const WM_USER = &H400
Global Const EM_SETREADONLY = (WM_USER + 31)

Declare Function SendMessage Lib "User" (ByVal hWnd As Integer ByVal wMsg As Integer, ByVal wParam As Integer, lParam As Any) As Long

SendMessage(Text1.hWnd, EM_SETREADONLY, 1, 0)

Cch trn ngi s dng vn c th Copy ni dung. Nu cn bn thc s cn cm ngi dng Copy ni dung, bn c th loi b t hp phm Ctrl-C bng cch "n nh" khi xy ra s kin KeyPress.

9. M file vi chng trnh lin kt (associated program)

1. Kim tra vic nhp liu vo TextBox
2. Chuyn i k t trong cc i tng c kh nng hiu chnh (Editbox) thnh ch hoa
3. B qua mt s k t khi g vn bn trong TextBox
4. Xa cc mc chn (Item) trong Combo/List Box
5. Lm sao  tt tnh nng Wordwrap ca Rich TextBox
6. Thm mt dng mi vo cui TextBox ang cha vn bn
7. Lm sao  Shut down hay Reboot li Windows ?
8. Lm cho TEXTBOX tr thnh read only hoc cm ngi dng thay i ni dung
9. M file vi chng trnh lin kt (associated program)
10. Lm sao  play cc file: MID, WAV ?

Hm Shell() hi b bt tin v ch gi c chng trnh trc tip t file exe. Khng ging nh Windows, th d nh khi double click ln file DOC s m Microsoft Word, file TXT s m Notepad. Bn cng c th vit mt Module to cc mi lin kt nh vy trong Visual Basic  d dng trong vic gi cc ng dng.

Cc khai bo API

#IF WIN32 THEN
Private Declare Function ShellExecute Lib "shell32.dll" Alias _ "ShellExecuteA" ByVal hwnd As Long, ByVal lpOperation As String, _
ByVal lpFile As String, ByVal lpParameters As String, _
ByVal lpDirectory As String, ByVal nShowCmd As Long) As Long

Private Declare Function GetDesktopWindow Lib "user32" () As Long

#ELSE
Declare Function ShellExecute Lib "SHELL" (ByVal hwnd%, _
ByVal lpszOp$, ByVal lpszFile$, ByVal lpszParams$, _
ByVal lpszDir$, ByVal fsShowCmd%) As Integer

Declare Function GetDesktopWindow Lib "USER" () As Integer
#END IF

Private Const SW_SHOWNORMAL = 1

Hm phc v vic khi ng

Function StartDoc(DocName As String) As Long

    Dim Scr_hDC As Long

    Scr_hDC = GetDesktopWindow()

    StartDoc = ShellExecute(Scr_hDC, "Open", _
    DocName, "", "C:\", SW_SHOWNORMAL)

End Function

Kim chng chng trnh

Private Sub Form_Click()

    Dim r As Long

    r = StartDoc("c:\mydoc\myletter.doc")

    Debug.Print "Return code from Startdoc: "; r

End Sub

10. Lm sao  Play cc file: MID, WAV ?

Bng cch s dng MCI ca Windows

Declare Function mciExecute Lib "MMSystem" (ByVal FileName as String) As Integer

Private Sub Form1_Click ()

iResult = mciExecute("Play c:\windows\mkmyday.wav")

End Sub

Tng t nh vy, bn c th dng cch ny  Play mt file MIDI. Cn y l cch Play mt file AVI

Private Declare Function mciExecute Lib "WINMM.DLL" (ByVal lpstrCommand as String) as Long

Private Sub Form_Click()

iResult = mciExecute("Play E:\Luu\AVI\Search.avi")

End Sub

Nu mun ngng, n gin bn ch cn thay t Play thnh Stop l c.

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03 th2 2002 05:52:45 CH
Nguyn H Thin ng

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