DIALOGS (COMMUNICATION DEVICE) IS USED TO DISPLAY INFORMATION AND RECEIVE INPUT FROM MOUSE OR KEYBOARD USERS DEPENDING ON THE SITUATION. THEY ARE USED TO FOCUS ATTENTION ON THE WORK OF CONTEMPORARY USERS OF THE PROGRAM SHOULD BE USEFUL IN OTHER WINDOWS PROGRAMS.
THERE ARE MANY TYPES OF DIALOGS, EACH APPLICABLE TO A PARTICULAR SITUATION. IN THIS CHAPTER WE WILL DISCUSS THE FOUR MAIN TYPES OF DIALOGS AND RESEARCH ON WHEN AND HOW WE USE THEM:
- Message Boxes
- Input Boxes
- Common Dialogs
- Custom Dialogs
Message Boxes
Message Boxes are used to remind what a user, and requires a certain response from the user. For example when we terminate MSWord program without filing the MSWord will prompt you store it with the following Dialog:
This image has been resized in order to avoid breaking the interface. Click here to view photo in full size (586x347)
In this case the user can click one of three buttons. If you click Yes , it will expedite the filing before the end of MSWord program. If you click No , the MSWord will quietly end. If you click Cancel , the change means that an end user program and return to continue using MSWord.
Routine we use MsgBox to display the Message Box like coding in the image below:
Parameter (parameter) is the first text message MsgBox Close the program down?,second parameter is a set of icons (vbQuestion) and some buttons (vbOKCancel) by adding the two constants: vbQuestion + vbOKCancel (two buttons OK and Cancel ), the third parameter title (title) of the Dialog.
This image has been resized in order to avoid breaking the interface. Click here to view photo in full size (685x224)
In the example above Constant MSWord icon and the buttons are vbExclamation +vbYesNoCancel (three buttons Yes, No and Cancel).
We choose the number and types of buttons in the table below:
Constant của các icons ta có thể dùng là vbCritical, vbQuestion, vbExclamation và vbInformation.
Constant Các buttons vbOKOnly OK vbOKCancel OK Cancel vbYesNo Yes No vbRetryCancel Retry Cancel vbYesNoCancel Yes No Cancel vbAbortRetryIgnore Abort Retry Ignore
When a Message Box is opened, the program stop and wait for user response. We say Message Box is displayed in Modal Mode , it is for all the attention and suspend the execution of the same program. After the user click a button, the Message Box will disappear and the program will continue running from just below the row of code MsgBox.
In the above example we use MsgBox as a sub, but we can also use the MsgBox function as a user to know just click any button. MsgBox function returns a value (return value) which we can then know which to implement. For example:
Private Sub CmdPrompt_Click()
Dim ReturnValue As Integer
ReturnValue = MsgBox("Close the program down", vbQuestion + vbOKCancel, "Exit Program")
Select Case ReturnValue
Case vbOK
MsgBox "You clicked OK"
Case vbCancel
MsgBox "You clicked Cancel"
End Select
End Sub |
You can display text messages in the Message Box in many rows using Constant vbCrLf (CarriageReturn and LineFeed) to mark the track breaks as follows:
Value Name Const 1 OK vbOK 2 Cancel vbCancel 3 Abort vbAbort 4 Retry vbRetry 5 Ignore vbIgnore 6 Yes vbYes 7 No vbNo
MsgBox "This is the first line" & vbCrLf & " followed by the second line" |
Public Sub DisplayError(ByVal ErrMess As String ) MsgBox ErrMess, vbCritical + vbOKOnly, "Error" End Sub |
Input Boxes
Message Boxes with, the user can click on a button. Sometimes we want to hit a little more user data, in the event that we can use the Input Boxes .Input Message Box Boxes seed varieties, but it specializes in getting data from user input and display an icon. For example:
Private Sub CmdGreeting_Click()
Dim strReply As String
strReply = InputBox$("Please enter your name", "What 's your name?", "John", 2000, 1000)
MsgBox "Hi " & strReply & ", it 's great to meet you!", vbOKOnly, "Hello"
End Sub |
Input Box có hai dạng Functions:
- InputBox$ - returns một String đàng hoàng
- InputBox - returns a String in the Variant variable
Here is an example using InputBox Function:
Private Sub CmdFortuneTeller_Click()
Dim varValue As Variant
Dim intAge As Integer
varValue = InputBox("Please enter your age", "How old are you?", "18")
If IsNumeric(varValue) Then
intAge = Val(varValue)
If intAge < 20 Then
MsgBox "You are a young and ambitious person", vbOKOnly, "Observation"
Else
MsgBox "You are a matured and wise person", vbOKOnly, "Observation"
End If
Else
MsgBox "Oh oh! - please type your age!", vbCritical + vbOKOnly, "Input Error"
End If
End Sub |
When to use Input Boxes
Although easy to use Input Boxes, in fact we rarely use it because of the following reasons:- You can not do anything while the user input data, must wait after the user clicks OK, then start handling input textstring. Conversely, if we use a regular textbox in a form, you can code in the handlers of Events Event KeyPress or Change to control the user's keystrokes.
- Input Boxes for only one type into a single text string. Sometimes we want user reviews on many things, so should have a separate form.
- Finally, Input Boxes unsightly view. Program seems to use Input Boxes are not professional, so we need to use Custom Dialogs .
Common Dialogs
You have noticed that almost all have the same programs in Windows to the Open and Save Dialogs files?And almost all programs have the same Dialogs to select the color, font, or to print? This is because the common belong Dialogs Common Dialog Library of MSWindows and the program calls for.Dialogs want to use it in VB6 we must reference Comdlg32.ocx by IDE menu command Project | Components ... and then click Apply Microsoft Common Dialog Control 6.0 .
Microsoft Common Dialog Control 6.0 Dialogs for our six types depending on what method to call:
Name Method Open File ShowOpen Save File ShowSave Color ShowColor Font ShowFont ShowPrinter Help ShowHelp
Open và Save File Dialogs
Open a new Project with a button named Form1 and type CmdOpen in the following code to Sub CmdOpen_Click:Private Sub CmdOpen_Click()
On Error GoTo DialogError
With CommonDialog1
.CancelError = True ' Generate Error number cdlCancel if user click Cancel
.InitDir = "E:\VB6" ' Initial (i.e. default ) Folder
.Filter = "Executables (*.exe) | *.exe| Batch Files (*.bat)| *.bat"
.FilterIndex = 1 ' Select ""Executables (*.exe) | *.exe" as default
.DialogTitle = "Select a program to run"
.ShowOpen ' Lauch the Open Dialog
MsgBox "You selected " & .FileName, vbOKOnly + vbInformation, "Open Dialog"
End With
Exit Sub
DialogError:
If Err.Number = cdlCancel Then
MsgBox "You clicked Cancel!", vbOKOnly + vbInformation, "Open Dialog"
Exit Sub
Else
MsgBox "Error in Dialog's use: " & Err.Description, vbOKOnly + vbCritical, "Error"
Exit Sub
End If
End Sub |
Let him run the program and click the Open button, program will display the errormessage below:
That's because we forgot to put a Microsoft Common Dialog Control 6.0 on Form1. So be it DoubleClick's icon in the Toolbox. Now run the program again and click the Open button to display the Open Dialog .
This image has been resized in order to avoid breaking the interface. Click here to view photo in full size (563x416)
You can choose any folder you like, by moving from this folder to another folder or disk drive change. If you click on the combobox to the right of the File of type , it will dropdown to show that you can choose one of two categories as listed in the Files statement:
.Filter = "Executables (*.exe) | *.exe| Batch Files (*.bat)| *.bat" |
After choosing a filename is available, or type a name into the File name text box, click Open . Then, CommonDialog1.Filename will contain the file name you have selected or entered.
Because for us. CancelError = True if the user should click Cancel the program willgenerate an Error 32 755 (cdlCancel). Here we catch that error by using the On ErrorGoTo Err.Number = cdlCancel DialogError and try to show the error message below:
Save Dialog is similar to the Open Dialog, ShowSave method we use to display it.
This image has been resized in order to avoid breaking the interface. Click here to view photo in full size (563x416)
In the above example we define the properties of CommonDialog1 by code. You can also use the Properties Windows to define them as follows:
Also, you can also use the Properties page of the Properties as defined CommonDialog1 to design by right click on Form1 and select Commondialog1 Properties :
Pages Dialog Properties tab displays the Open / Save As is available at the beginning, you can type the following information:
Color Dialog
Color Dialog to the user selecting a color easy to use. Besides the color is available, users can create and then give it a color palette to be added to the offer, called the Windows palette by clicking the button Add to Custom Colors .
This image has been resized in order to avoid breaking the interface. Click here to view photo in full size (771x358)
You create a color by clicking where it has the color palette in the big square and then hold triangle to the right to pull up, pull down to change the color saturation of the square box shown in the Color | Solid .When satisfied with the color display, click the button Add to Custom Colors , color would be added to the group Custom Colors located below, left.
We use the method ShowColor to display the Color Dialog. After the user has selected a color, then we can assign it directly to the ForeColor or BackColor property of a control. In the example below which the user has selected a color for the background of the picturebox is gán Picture1:
Private Sub CmdSelectColor_Click()
On Error GoTo NoColorChosen
With CommonDialog1
.CancelError = True
' Entire dialog box is displayed, including the Define Custom Colors section
.Flags = cdlCCFullOpen
.ShowColor ' Launch the Color Dialog
Picture1.BackColor = .Color ' Assign selected color to background of Picture1
Exit Sub
End With
NoColorChosen:
' Get here if user clicks the Cancel button
MsgBox "You did not select a color!", vbInformation, "Cancelled"
Exit Sub
End Sub |
Font Dialog
Font Dialog was chosen for the screen or printer fonts and colors to choose the font used for text. We use the method ShowFont FontDialog to display. The information presented in the Font Dialog depending on the value Flags are as follows:If you want the user to select arbitrary color, then add 256 to the value of the Flags.
Constant Value Effective cdlCFScreenFonts 1 Show only the printer fonts support cdlCFPrinterFonts 2 Fonts only display of the screen, not necessarily all printer support cdlCFBoth 3 Hiien marketing the screen and printer fonts cdlCFScalableOnly &H20000 Scalable display only TrueType fonts as fonts that you have installed on your computer
Here is the code for the user to select the font and color of Label1.
Private Sub CmdSelectFont_Click()
On Error GoTo NoFontChosen
CommonDialog1.CancelError = True
' Causes the dialog box to list only the screen fonts supported by the system.
CommonDialog1.Flags = cdlCFScreenFonts + 256 ' Add 256 to include Color option
CommonDialog1.ShowFont ' Launch the Font Dialog
With Label1.Font
.Bold = CommonDialog1.FontBold
.Italic = CommonDialog1.FontItalic
.Name = CommonDialog1.FontName
.Size = CommonDialog1.FontSize
.Strikethrough = CommonDialog1.FontStrikethru
.Underline = CommonDialog1.FontUnderline
End With
Label1.ForeColor = CommonDialog1.Color
Label1.Caption = "Hello world!!!, this is a Font Dialog Demo"
Exit Sub
NoFontChosen:
MsgBox "No font was chosen!", vbInformation, "Cancelled"
Exit Sub
End Sub |
You can download the source code of this program FontDialog.
Print Dialog
Print Font gives us an interface similar to Microsoft Office in order to choose the elective on printing. With the Print Dialog you can select any printer with features that by clicking the button Properties button or Preferences . We can also decide to print from page to page of document and print as many copies. Only thing to note is that if users use the Print Dialog to select a different printer in Print Dialog which I have chosen Property PrinterDefault = True then it will become a Default Printer Printer and it will be permanently in effect until both Windows when the user changes again.Unlike Color and Font Dialogs, Print Dialog does not require us to give a Flags value of the Property. I just use Method ShowPrinter to display the Print Dialog. The three most commonly used properties after the user select the Print Dialog is arbitrary Copies, FromPage and ToPage . To give users the default values of these properties, you can leave the available values before displaying the Print Dialog.
Below is a sample code using print dialog:
Private Sub CmdSelectPrinter_Click()
With CommonDialog1
.FromPage = 1
.ToPage = 1
.Copies = 1
.ShowPrinter
End With
End Sub |
Help Dialog
We use the method ShowHelp to display help information, but remember to give at least CommonDialog value of the properties HelpFile and HelpCommand .Private Sub CmdHelp_Click() CommonDialog1.HelpFile = "YourProgram.hlp" CommonDialog1.HelpCommand = cdlHelpContents CommonDialog1.ShowHelp End Sub |
Custom Dialogs
Many of the Message Box, Input Box or the Common Dialogs format is not appropriate for situations programming. In the event that you can use a normal form to make a Dialog house plants, garden leaves. It takes quite a bit more work, but first it has the same color as other Forms in the program, and secondly we want to do anything you want. The only disadvantage is that the program will use more resources, to be frank is a little more memory.Here we try to develop a generalized Login Form, can be used in many cases. On startup, this program will display a Login form requires users type in a username and password. Then, if a valid username and password, then the main form of the new program appears. How is the program we made a start with Sub Main in. BAS module. Sub Main calls the Sub GetUserInfo (also in the same module) to display the form frmLogin in Modal mode so it works the same way as the Message Box, Input Box or Common Dialogs.
Once the form frmLogin hidden by the execution of the statement Me.Hide SubGetUserInfo will continue to detail and fill in the textboxes txtUserName txtPasswordreturned and local variables strUserName strPassword. Source of the Sub Main andSub GetUserInfo are listed below:
Sub Main()
Dim strUserName As String
Dim strPassword As String
' Call local Sub getUserInfo to obtain UserName and Password
GetUserInfo strUserName, strPassword
If strUserName = "" Then
MsgBox "Login failed or aborted", vbInformation, "login Aborted"
Else
MsgBox "User " & strUserName & " logged in with password " & strPassword, vbInformation, "Login accepted"
' Check UserName and Password here
' If valid password then show the Main form of the program which is implemented separately...
' frmMain.Show
End If
End Sub
Private Sub GetUserInfo(ByRef sUserName As String, ByRef sPassword As String)
' Invoke frmLogin form in Modal mode
frmLogin.Show vbModal
' As soon as frmLogin is hidden, the execution gets here
sUserName = frmLogin.txtUserName ' assign the form's txtUserName to sUserName
sPassword = frmLogin.txtPassword ' assign the form's txtPassword to sPassword
Unload frmLogin ' Unload form frmLogin
End Sub |
After users enter information and click OK , it is only temporary display a message to confirm the details he.
In the future, you can write code to check the name and password are not valid. There are a few details about its form frmLogin to work just like a Common Dialog:
- Ta for the BorderStyle property is frmLogin Fixed Dialog.
- Property of the textbox we PasswordChar txtPassword with "*" as the user to enter a password, I just saw a row of asterisks.
- It is of the form is CenterScreen StartupPosition Property.
- Default property of True cmdOK button to the user pressing the Enter key in forms isconsidered equivalent to cmdOK click button..
- Similar way, Property Cancel button of cmdCancel is True the user to press Esc in the form is considered equivalent to cmdCancel click button.
Private Sub CmdCancel_Click() ' Clear txtUserName and txtPassword txtUserName = "" txtPassword = "" ' Hide the Form to get out of Modal mode Me.Hide End Sub Private Sub CmdOK_Click() ' Hide the Form to get out of Modal mode Me.Hide End Sub |
(Collected)
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