I am new to VB.Net and created an MDI container in which two child forms "Account_Master" and "F1List" are created. When I open "Account_Master" form and press the F1 key on its TextBoxAccountName, it should open the F1List form which is working ok. After open the F1List, when I enter the text in TextBoxList and Click on Button1, the entered text should be passed to Account_Master's TextBoxAccountName and F1List should close. But this is not happening. here is my code. Please help.
'Form Account_Master code
Private Sub Account_Master_KeyDown(ByVal sender As Object, ByVal e As KeyEventArgs) Handles MyBase.KeyDown
If e.KeyCode = Keys.F1 Then
Dim f As New F1List
f.Show()
End If
End Sub
'form F1List code
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Account_Master.TextBox1.Text = TextBoxList.Text
Me.Close()
End Sub
That second code snippet is referring to the default instance of the Account_Master form class. If you didn't display the default instance in the first place then you're making a change to a form other than the one you're looking at. As an example, the first code snippet is NOT displaying the default instance of F1List but, rather, creating an instance explicitly. Displaying the default instance would look like this:
If e.KeyCode = Keys.F1 Then
F1List.Show()
End If
As with your second code snippet, you access the default instance via the class name. If you want to be able to use the default instance later then you need to use the default instance to start with. You can't really mix and match. Most experienced developers would not use them at all, myself included, but use them properly if you're going to use them at all.
Related
Currently in my windows form, I have a few WinForms to work with. One WinForm acts as a main menu and is supposed to call another form as a secondary window on its own.
Private Sub btnMainGame_Click(sender As Object, e As EventArgs) Handles btnMainGame.Click
' This is the button to call up the main game controller. So simply hide this form aned then open the new form.
Dim frmController As New frmControllerScreen
frmController.Show()
Me.Hide() ' Happens on .Close as well
End Sub
The above code invokes another WinForm which is used to handle more options. When the user clicks on a particular button, a sub form is created again.
Dim OpenNewGameWindow As New frmGameConfig
OpenNewGameWindow.ShowDialog(Me)
Me.DialogResult = DialogResult.None ' Used to prevent the subform from closing the main form when it catches a dialog result.
Now in the frmGameConfig, the program is supposed to take data and pass it back to the form that called it.
Private Sub btnNewGameStartGame_Click(sender As Object, e As EventArgs) Handles btnNewGameStartGame.Click
' ... Skipped code...
frmControllerScreen.MasterQuestionList = QuestionList
frmControllerScreen.blnBankedTime = cbBankedTime.Checked
' ... Skipped code...
End Sub
However, when the frmController tries to reference MasterQuestionList... it returns a nullreference error as if it was not set.
Here's where things get funny...
When I made this code, frmControllerScreen was actually the startup form. Now when I change this form back to frmMainMenu, I get NullReference errors constantly.
My question: How am I supposed to pass information from one form to the next form if it was instantiated from a parent form. (Note I even moved the declartion to Public as a "module-wide" variable... and nothing happens but the same result.) The same error happens even if I go ahead and declare frmController.MasterQuestionList as well.
Instead of trying to pass data back from the called form to the caller, you can reference the called form's controls from the calling code after .ShowDialog.
Dim OpenNewGameWindow As New frmGameConfig
If OpenNewGameWindow.ShowDialog() Then
MasterQuestionList = OpenNewGameWindow.QuestionList
blnBankedTime = OpenNewGameWindow.cbBankedTime.Checked
End If
In OpenGameWindow button click:
Private Sub btnNewGameStartGame_Click(sender As Object, e As EventArgs) Handles btnNewGameStartGame.Click
Me.DialogResult = True
End Sub
I write this code for tab-like behavior when user presses ENTER on textboxes for every form, which works fine.
If e.KeyChar = Microsoft.VisualBasic.ChrW(Keys.Return) Then
SendKeys.Send("{TAB}")
e.Handled = True
End If
However, I need to write the code once, perhaps as a sub or function in a module so that I do not have to write the same for every form. I have checked various forums including
Detecting Enter keypress on VB.NET and
Tab Key Functionality Using Enter Key in VB.Net
BUT all I get is either to write code for each textbox or for every individual form.
Has anyone tried out a single code for ALL or may be several selected forms of the application? If yes, please share with me. Writing for every form still works fine for me but i need to take advantage of OOP. Thanks
There are many ways to implement this, one of those is to create a custom textbox User Control
Adding a control to your project is very easy just right click in your project in the solution explorer ->Add->User Control
Give a name to your control ex. "tabedtextbox"
Add a textbox control to your User Control
Place the code in the keypress event of textbox1 of the UserControl
Private Sub TextBox1_KeyPress(sender As Object, e As KeyPressEventArgs) Handles TextBox1.KeyPress
If e.KeyChar = Microsoft.VisualBasic.ChrW(Keys.Return) Then
SendKeys.Send("{TAB}")
e.Handled = True
End If
End Sub
Compile once in order to update the whole project with the new user control.
Goto to your form and add your new User Control, you can locate it at the Toolbox panel.
Run your program and you will see the behavior of TAB when you press enter on each textbox.
If You wish to allow the user to press enter in a TextBox, instead of pressing a specific button,
you can use the acceptbutton property.
One good way to use it, is to change the property, on the Enter and Leave events of the TextBox. That you call Click event of the Button, when User press Enter inside the TextBox.
Try this code:
Private Sub tbProject_Enter(sender As Object, e As EventArgs) Handles tbProject.Enter
Me.AcceptButton = bSearch
End Sub
Private Sub tbProject_Leave(sender As Object, e As EventArgs) Handles tbProject.Leave
Me.AcceptButton = Nothing
End Sub
Private Sub bSearch_Click(sender As Object, e As EventArgs) Handles bSearch.Click
'.... actions to perfom
End Sub
Screen
Is there any way to do the following, other than hiding then closing the hidden form later?
Mainform opens SecondForm as show dialog, i need to Open ThirdForm from SecondForm while closing SecondForm while keeping third form acting as "showdialog" on the MainForm?
When you show SecondForm(), pass in MainForm() as the owner to ShowDialog():
Public Class MainForm
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim sf As New SecondForm
If sf.ShowDialog(Me) = Windows.Forms.DialogResult.OK Then
' ... do some processing in here ...
End If
End Sub
End Class
Now, in SecondForm(), you can then set the owner of ThirdForm() to that of SecondForm():
Public Class SecondForm
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Me.Hide()
Dim tf As New ThirdForm
tf.ShowDialog(Me.Owner)
Me.DialogResult = Windows.Forms.DialogResult.OK
End Sub
End Class
You could simply open the third form from the main form as soon as the second form returns a dialog result
You also might want to look at MDI this gives you more control over what the user can and can't do.
After trying Idle_mind suggestion it was still giving me problems going back and forth between forms continously showing them as .showdialog. I solved my problem just like tinstaafl suggested. I wish i would have got his message before a couple hours of trying different methods before coming up with this one.
When i close each form, i set a boolean flag in the main form. then i call a sub that is in the main form to show the next form as showdialog from the main form. i use the flag which triggers logic in the form im loading whether or not to bind data from datatable so i can edit it.
sorry with all those forms i know it gets confusing. to sum it up, close the dialog form (me.close), set flag so calling code knows what to do once the showdialog code is satisfied.
VB2010. I must be missing something because I couldn't find a solution after searching for an hour. What I want to do is simple. In my app I want to display a modeless form so that it is floating while the user can still interact with the main form.
dim f as New frmColors
f.Show(Me)
But I only want one instance of the form at any time. So how can I prevent more than once instance being displayed, and if there is one instance then just give it focus?
Does something like this work for you, if the form is already visible you can not do a Show, you can just do a BringToFront, also you can check to see if the Form has been disposed so you can New up another one.
Public Class Form1
Dim f As New frmColors
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
If f.IsDisposed Then f = New frmColors 'To handle user closing form
CheckForm(f)
End Sub
Private Sub CheckForm(frm As Form)
If frm.Visible Then
frm.BringToFront()
Else
frm.Show(Me)
End If
End Sub
End Class
Make your form follow the singleton pattern. I can't vouch for this sample, but from the text it appears to do what you want.
I have a mdicontainer form that summons forms. My problem is when the a user clicks again the menu for that form, it also make another instance of it.
What I did is declare a public class with a public variable on it ex: Boolean isFormOneOpen = false. Then every time formOne opens, it checks first the global variable I declared a while ago if it's false, if it is, instantiate an object of a formOne and then show it. Otherwise, do nothing. Very static, imagine if I have many forms, I have to declare a variable for each form to check if it's already open. Can you provide me a solution for this? Maybe a method that accepts a Form? Or any more clever way to do this.
You don't need a variable, you could iterate the MdiChildren collection to see if the form is already opened. For example:
Private Sub btnViewChild_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnViewChild.Click
For Each child In Me.MdiChildren
If TypeOf child Is Form2 Then
child.WindowState = FormWindowState.Normal
child.Focus()
Exit sub
End If
Next
Dim frm As New Form2
frm.MdiParent = Me
frm.Show()
End Sub
The VB.NET-centric solution:
Private Sub btnViewChild_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnViewChild.Click
Form2.MdiParent = Me
Form2.WindowState = FormWindowState.Normal
Form2.Show
End Sub
Rather than a boolean, declare a variable of the form's type. Then just make sure the variable isn't Nothing and call it's .Open() method. This has the nice side effect of also bringing your existing form instance to the front if it's already open.
Even better, in VB.Net 2.0 and later all forms have a default instance with the same name as their type, so you can just say FormName.Open() and be done with it. However, I haven't tried this in an mdi situation before.