*edit: OK, so this is my real problem, below scenario happens only when the form is MDIChild.. thanks for anyone that could provide me with the code
I have a form with labels, panels, buttons etc. Where I'm having problem is, while form2 is my active window/form and I clicked on a control inside form1, the form1 does not activate itself. What I would like to happen is for form1 to activate even when it's not the form I clicked, only the control inside it (any control)..
I'm thinking that if I clicked a control on the form, there's an event fired on the form. If I could only know of that certain event, that would help - maybe (coz I could just add Me.activate on that event if it exists). I've tried searching for series of events when a control (ex. label) is clicked but to no avail. I hope that someone could help me with this one.
Thanks in advance.
*edit
i will just try to make my question more understandable..
How can I activate the form when only the control is clicked (say, label or textbox)? My forms does not activate or focused when I click inside it except the form itself..
I can do this on one control..
Private Sub Label1_Click - Handles Label1.Click
Me.Activate()
End Sub
But what if I have 20 controls (labels, buttons, textbox, combobox, etc)? See? =)
EDIT: this answer does not apply to MDI applications.
I think what you really want to know is which one of your forms is currently the foreground window (if any). The first thing you need to understand is that a form instance lives inside a window, but the window's behavior is controlled somewhere higher up. Similar to how a form instance is identified by a variable pointing to the instance, a window can be identified by what's known as a window handle.
Knowing this, the proper way to find out whether a form is the "active" form is to:
find out the window handles of the windows containing our instances of Form1 and Form2
find out the window handle of the foreground window (which can be any window)
compare the value found in step 2 to all of the values found in step 1
Perhaps you'd then like to fire an event if the foreground window changes, but I'll leave the actual implementation up to you. There are probably several ways to perform step 1 and 2, but I can't give any solutions off the top of my head. Hopefuly I've put you back on the right track.
EDIT
Alternatively, you can use the form's Containsfocus property. If its value is True, you can safely assume that your form is the foreground window. I didn't find out about this property until after I wrote my own implementation, which I'll show you anyway:
One module containing only a windows API call
Friend Module NativeMethods
Friend Declare Function GetForegroundWindow Lib "user32.dll" () As IntPtr
End Module
Calling this method will return the window handle of the foreground window (if any).
One module containing the extension method for the Form class
Imports System.Runtime.CompilerServices
Public Module FormExtensions
<Extension>
Public Function IsForeground(f As Form) As Boolean
Return (f.Handle = NativeMethods.GetForegroundWindow)
End Function
End Module
Calling this method returns whether the specified form f has the same window handle as the foreground window.
Usage example
You could use a Timer that periodically checks whether a form is the foreground window.
Public Class Form1
Private WithEvents timer As New Timer With {.Enabled = True}
Private Sub timer_Tick(sender As Object, e As EventArgs) Handles timer.Tick
If Me.IsForeground() Then
Console.WriteLine("this instance of Form1 is the foreground window")
End If
End Sub
End Class
Like I said before, you can use Me.ContainsFocus instead of my extension method and it will work just fine.
In non-MDI forms, the form is automatically activated when you click any control inside it.
Related
My problem pertains to a COM add-in for Microsoft Excel. The use case is as follows: 1. User clicks the add-in's button on the ribbon. 2. A form window appears. 3. User interacts with the form window and clicks an OK button. 4. Various reports are generated, while a progress bar on the form window shows progress. 5. At the end of the process, the form window closes.
The process works as designed on the first run, but after the form window has been closed there is no way to start a new "session." From the user's perspective the add-in button becomes non-responsive. When run in debug mode from Visual Studio, clicking the add-in button a second time generates an error message: "Cannot access a disposed object."
Clearly something is wrong with the way I have hooked everything up, but I haven't been able to find a simple description of how to do it correctly. Here is what I have:
In a public class a number of public (or "global" variables) are declared; the form is also declared and instantiated here:
Public Class GlobalVariables
Public Shared FormInstance As New MyFormDesign
End Class
The reason for declaring the form as a public object is to be able to be able to send progress values from various different subs and functions. The GlobalVariables class is imported by all modules that require it.
Behind the ribbon button is a single line of code:
FormInstance.Show()
Clicking the button instantiates and shows the form as intended. To keep things simple we can ignore the bulk of the code; simply clicking the "Cancel" button will trigger the problem. The code behind the "Cancel" button is straightforward:
Me.Close()
GC.Collect()
After closing the form it is no longer possible to create a new instance, per the error message cited above.
I don't really understand what is going on here, but it looks to me like the GlobalVariables class, once created, persists until the end of the Excel session. If that is correct the problem could presumably be cured by instantiating the form in a standard module. Instead of attempting to revive a form that has been disposed, the add-in would just create a new instance each time the user clicks the button. But if I go that route I can't figure out how to send progress values from other subs back to the form. It seems like a Catch-22.
There has got to be a way to both (a) create the form as a public object, and (b) create and destroy a new instance each time the add-in is run. Right? What am I doing wrong?
It has been a long journey, but I finally found out how to build the functionality described in my question. I will post the answer here, as it may help others in the future.
The challenge was to declare a form as Public in order to make it accessible throughout the project, so that subs and functions can send progress updates back to the form.
The problem was that the form, when declared and instantiated as described in my question, can only be created once per Excel session.
The solution is to declare the form as Public without instantiating it, then access it via a Public ReadOnly Property.
First, declare FormInstance as a public variable without instantiating it:
Public FormInstance As MyFormDesign
Second, define a Public ReadOnly Property. This establishes a way to call the form:
Public ReadOnly Property CallMyForm() As MyFormDesign
Get
Return FormInstance
End Get
End Property
Third, the ribbon button's Click event instantiates and shows the form:
Private Sub Button1_Click(sender As Object, e As RibbonControlEventArgs) Handles Button1.Click
FormInstance = New MyFormDesign
FormInstance.Show()
End Sub
Now a new form instance will be created each time the ribbon button is clicked, but the form can still be accessed via the CallMyForm property.
Instead of ...
FormInstance.BackgroundWorker1.ReportProgress(i)
... we will use:
CallMyForm.BackgroundWorker1.ReportProgress(i)
This solves the conundrum laid out in the question.
The VB.Net program I am creating dynamically created Panels within a TableLayoutPanel and adds form elements to them. I need to keep track of what the last of these Panels to have focus was, and am hitting a bit of a brick wall.
I have tried creating an event class for when the Panel has focus:
Private Sub Self_GotFocus(ByVal sender As Object, ByVal e As EventArgs) Handles Me.GotFocus
GlobalController.Focus_Target = Me.Name
End Sub
The classes for each Panel Inherit from Windows.Forms.FlowLayoutPanel, which I why I have the call being Me.GotFocus. Additionally, the GlobalController class is just a class meant to hold global variables for the program.
Now the issue I am having, is that this event only seems to trigger when I actually am deleting the panel. When the panel is created, if I click on it, or any of it's form elements, the event never gets triggered (I debugged the program with a breakpoint).
I can't exactly figure out why this only triggers when I go to delete the panel, and not at any other time. Is there another event I should be using instead of GotFocus?
Use .Enter event in your panel since GotFocus is related only to focused control (not it's parent), mostly when UICues is set.
See MSDN GotFocus
I have a user control that I created with certain buttons, and I placed it within the main form, which already contains things like buttons and panels. I want to control(send messages) to these fields when I press the buttons in the user control, but I can't figure out the OOP implementation required to achieve this.
I was advised to create an Initialize(f as Mainform) in the user control code in order to keep an explicit reference to the main form, but I have not been able to control the fields of the main form.
How can this be achieved? I am using visual basic, btw.
Declare an event in the user control, and then write a handler for that event in the form.
In the control:
Event Zoomed()
In the control, to raise the event (call the handler):
RaiseEvent Zoomed()
and add the handler to the form:
Sub aview_zoomed() Handles aView.Zoomed
...
End Sub
I have a customer which as a Visual Basic Project in single instance mode with a wired presentation logic.
The main form contains a TabControl with mutliple TabPages.
If I click on TabPageA another form is shown in front of the Form and resized to have the same size as the TabPage.
If I click on TabPageB the first form is hidden and another form is displayed.
So basically for the user it looks like you have a TabControl with different TabPages which is not the case.
I tried converting the Forms to UserControls and put them inside the TabPage, but, thanks to the SingleInstance app, this would take a whole lot of refactoring. I tried it but eventually gave up because of many many runtime errors and I don't want to put any more effort in this.
My Ideam was that, at runtime, I could add the forms to the TabPages and let them act like UserControls, is this even possible?
You can turn a Form class back to a child control by setting its TopLevel property to False. It becomes essentially a UserControl with some unused overhead. Make it look similar to this:
Public Class Form1
Public Sub New()
InitializeComponent()
Dim frm As New Form2
frm.TopLevel = False
frm.FormBorderStyle = Windows.Forms.FormBorderStyle.None
frm.Visible = True
frm.Dock = DockStyle.Fill
TabPage1.Controls.Add(frm)
End Sub
End Class
Any window can be hosted in any other window (a Control is a window, technically) using SetParent.
<System.Runtime.InteropServices.DllImport("user32.dll")>
Public Function SetParent(ByVal hWndChild As IntPtr, ByVal hWndNewParent As IntPtr) As IntPtr
End Function
to declare and
SetParent(FormToHost.Handle, ControlToHostForm.Handle)
to use. It may not be ideal but it's okay if you don't want to put any more effort into this, like you say. The forms will maximize and minimize properly, and will not show up in the taskbar, and will close with their containers.
you can use panels. in each tab different panel or panels must be show an the other or others must be hide.
I'm trying to create a user control in my code behind, and then respond to events in that control. Presumably because the control doesn't exist at compile time, Visual Studio can't compile the handler subroutine I created to catch my control's event. Importantly, I want to decide the type of control at runtime (which is why I'm not just hard-coding it).
[before going on, the controls work correctly, including events and event handlers when used in the 'normal' way of creating the controls in XAML. I want to create the control instances in code behind so I can avoid duplicating pages that are 99% identical]
This 'works' (but doesn't give me the flexibility I need):
Public WithEvents AnswerPanel As MyControls.ScrollerControl
... (and the initialisation in the New() sub):
AnswerPanel = New MyControls.ScrollerControl
ItemStack3.Children.Add(AnswerPanel)
AddHandler AnswerPanel.GuessMade, AddressOf CheckAnswer
... (this is the handler sub responding to a custom event in the ScrollerControl)
Public Sub CheckAnswer(answer As String) Handles AnswerPanel.GuessMade
With the code above everything works as I expect: the control is created at runtime and its event is handled correctly.
What I want to achieve is to be able to choose a different user control when I initialise my control (e.g. ScrollerControl2, ScrollerControl3, etc.) I can create the controls this way by changing the first line to:
Public WithEvents AnswerPanel As UserControl
But once that change is made I can no longer reference the custom event in my handler as (presumably) the compiler sees it as a generic UserControl, which doesn't include my custom GuessMade event. The compiler errors on the event name and tells me it doesn't exist.
I'm sure I'm doing something wrong here. I think it's a theory/concept issue rather than my code.
Am I on the right track or going about this in the wrong way?
If I am reading this right, you have a user control that fires an event and you want the parent page to catch that even? If so, you need to raise the event, which will cause the event to bubble to the the parent. IE:
Partial Class user_controls_myControl
Inherits System.Web.UI.UserControl
Public Event DataChange As EventHandler
End Class
This creates a control with a public event called DataChange. Now, if you look at the code in the parent page that instantiates the user control, you will see that it has an event called "OnDataChange". Just like an onCLick event, you can assign this a method in the parent page. Now, you just need to raise the event in the user control. This can be added in some event in the control, like a button click or radio button change event:
RaiseEvent DataChange(Me, New EventArgs)
This takes two objects, the sender and event arguments. Typically I pass ME, which is the user control. This is great because you can use reflection to get all the controls public properties. You can also use this to cast objects to your control type. I rarely pass event arguments but you certainly could.
I answered a similar question here: Handling events of usercontrols within listview
If this is not what you had in mind, let me know
EDIT: To add a user control dynamically and attach the event:
First, in the page that will be using the control, you will need to add a place holder:
<asp:PlaceHolder ID="placeholder1" runat="server"></asp:PlaceHolder>
as well as a reference to the user control at the head of the page (depending on how the page is setup, you may not need this. If you get a page directive error, remove it):
<%# Reference="" Control="~/user_controls/myControl.ascx"%>
In the parent page, you can then create a user control and add it to the place holder. You must declare the user control with events like this:
Private WithEvents myNewControl As New user_controls_myControl
then, in some method you can add it to the page like this:
Dim getPh As New PlaceHolder
'create an instance of the user control
newMyControl = CType(LoadControl("~/user_controls/myControl.ascx"), user_controls_myControl)
'get a handle on the place holder
getPh = me.placeHolder1
'add the user control to the place holder
getPh.Controls.Add(newMyControl)
Then, make sure you have event method:
Protected Sub myEvent(ByVal sender As Object, ByVal e As EventArgs) Handles myNewControl.DataChange
End Sub
So, if you added the RaiseEvent to the user control like I suggested earlier, this should work for you.
I have an answer to this now. As I suspected I was sort of thinking about the problem from the wrong angle.
In a nutshell I was trying to raise an event from my user controls, but I needed to be raising the events in the base class and calling that from my user controls.
So my base class (which my user controls inherit from), now contains the following:
Public Event GuessMade(answer As String)
Protected Sub RaiseGuessEvent(answer As String)
RaiseEvent GuessMade(answer)
End Sub
Then, in my user control(s), when I need to raise the event, I simply call the RaiseGuessEvent sub like this:
Me.RaiseGuessEvent(CurrentValue)
And additionally, I had to remove the event from my subclasses/user controls, of course.