How do I make a keydown event inside another event?

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I want to be able to exit a new form I created, but since I manually made the form its does not have a handler in the withevents. So since I can not figure out for the life of me how to approach getting my form into the withevents, I came up with another possible solution.

I figured that I could make a keydown event inside the event that populates the new form. Right now it's not working, but I was hoping to ask someone if I am on the right track, and possibly if they know what I need to change?

Here is my code:

Dim dk As System.Windows.Forms.KeyEventArgs
     dk = sender
     If dk.KeyCode = Keys.Escape Then
             picform.Close()
         End If

What I have tried:

I have tried changing the dk value into an integer and also tried changing it to a key value, none have helped.

Posted 23-Jul-17 21:32pm

Member 11856456

Updated 24-Jul-17 9:09am

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Graeme_Grant · Answer 1 · 2017-07-23T22:16:00

Solution 1

Refactor (extract) the code into a new method (Sub/Function). Then you can call it from multiple places in your code. Example:

BEFORE:

VB

Public Class Form1

    Private Sub Form1_KeyDown(sender As Object, e As KeyEventArgs) Handles MyBase.KeyDown

        ' code does something here!

    End Sub

End Class

AFTER:

VB

Public Class Form1

    Private Sub Form1_KeyDown(sender As Object, e As KeyEventArgs) Handles MyBase.KeyDown

        NewMethod()

    End Sub

    Sub NewMethod()

        ' code does something here!

    End Sub

    Sub OtherMethod()

        NewMethod()

    End Sub

End Class

Updated with new requirement: For the new requirement, you need to use WithEvents to capture the KeyDown event.Here is a new example to reflect this.

VB

Public Class Form1

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        OpenForm()
    End Sub

    Private WithEvents picform As New Form

    Sub OpenForm()

        picform.Height = 800
        picform.Width = 600
        ' picform.FormBorderStyle = FormBorderStyle.None
        picform.Show()

    End Sub

    Private Sub picform_KeyDown(sender As Object, e As KeyEventArgs) Handles picform.KeyDown

        MsgBox("Picformn keydown event caputred in parent form", MsgBoxStyle.Exclamation)

    End Sub

End Class

Posted 23-Jul-17 22:16pm

Graeme_Grant

Updated 23-Jul-17 23:27pm

v2

Comments

Member 11856456 24-Jul-17 4:22am

The only problem is where it says mybase.keydown, it suppose to be picform.keydown. I cant find this event in the withevents section, but I can see the form1. I need to call forth picform to perform this function. any suggestions?

Graeme_Grant 24-Jul-17 4:31am

The Keydown event is for a form or control?

I read it for the form - ie: picform. The only difference is that my Form is called Form1. In Visual Studio's Properties toolbox, click on the lightning-bolt and all events for the form or control are listed.

If you mean the PictureBox control, use the PreviewKeyDown event instead.

Ralf Meier 24-Jul-17 4:44am

Perhaps you should provide the COMPLETE code to the issue ...
For me it's impossible to give you an answer with this less Information ...

Member 11856456 24-Jul-17 5:05am

so I have created this form,

Dim picform As New Form
picform.Controls.Add(control)
picform.Height = 800
picform.Width = 600
' picform.FormBorderStyle = FormBorderStyle.None
picform.Show()

but this is in another event, so I can not get a handle from it. So I am trying to figure out a way to close the newly created form from an escape key press.

Graeme_Grant 24-Jul-17 5:29am

See update above.

When asking questions, you need to spell out exactly what you are trying to do, then you will get a better answer the first time.

Member 11856456 24-Jul-17 5:42am

Im getting a "Cannot access a disposed object". this is close to what I need problem is when I go to create another form which is picform thats when i get that error.

Ralf Meier 24-Jul-17 5:33am

I'm not complete sure what you mean.
But if you Show picForm then picForm normally has the Focus - so the action (and the Events) comes from picForm.
If you want to have picForm-Events outside from picForm you should instance it with WithEvents :
>public WithEvents picForm as new Form<
But this can't be done inside a method. For this you must declare picForm outside your method (because you want to use it's Events Independent from this method).

Graeme_Grant 24-Jul-17 5:51am

... as per the above code in solution ;)

Ralf Meier 24-Jul-17 6:02am

You are right - sorry - I haven't seen that.
But I think, the Enquirer doesn't realize that ... :(

Ralf Meier 24-Jul-17 6:06am

I think, he instances the Form inside the Button.Click-method ...

Graeme_Grant 24-Jul-17 6:07am

yesss....

Ralf Meier 24-Jul-17 6:26am

by the way - take a look to here :
https://www.codeproject.com/Questions/1197425/Why-cant-I-use-a-handler-for-a-new-form

Graeme_Grant 24-Jul-17 6:30am

lol... the same guy hey...

Member 11856456 24-Jul-17 6:42am

yeah, I couldnt get an appropriate answer to it. your answer helped on this, but its not 100% what I am looking for. it does allow me to add that picform as withevents which is a step in the right direction. I am still researching this, I have been doing this one problem for about a week. Its extremely frustrating lol, but its a good learning expereince.

Ralf Meier 24-Jul-17 9:17am

You couldn't get an appropriate answer because you're not able to ask the question in the right way AND you're not willing to give the necessary Information. Remember : we are not sitting beside you - we can't see what you see ...

Member 11856456 · Answer 2 · 2017-07-24T09:09:00

Solution 2

So thanks to Graeme_Grants solution I was able to figure out the rest, I just needed a way to get the withevent handler.

 Private WithEvents picform As New Form

Dim picform As New Form
        picform.Controls.Add(expandpic)
        picform.Height = 800
            picform.Width = 600
        ' picform.FormBorderStyle = FormBorderStyle.None
        picform.Show()

        AddHandler picform.KeyDown, AddressOf picform_convert

    End Sub

    Private Sub picform_convert(ByVal sender As System.Object, ByVal e As KeyEventArgs)

        picform = CType(sender, Form)

        If e.KeyCode = Keys.Escape Then
            picform.Close()
            picform.Dispose()
        End If

    End Sub

Just figured out the rest, thanks for the help. now I know how to call forth an withevent handler for future reference.

Posted 24-Jul-17 9:09am

Member 11856456

Comments

Dave Kreskowiak 24-Jul-17 15:23pm

WithEvents just means that event handlers specifying the Handles clause are wired up for you. If you can't use WithEvent, you have to wire up the events yourself with AddHandler, like you've done in your example.

Your example is a bit flawed. You're creating a new form instance variable, "picform", that is scoped inside a method and then showing in non-modal. Immediately after this method exists, the picform variable goes out of scope and the form you launched will eventually die when the garbage collector gets around to seeing that nothing holds a reference to it.

Your current form should also NOT be handling the events of another form. This is very bad practice, forever tying the two forms together. One cannot be reused without the other. The concept is called "separation of concerns". The picform should have been designed separately and the code to handle key presses put in that forms code, NOT in the code of another form.

Member 11856456 24-Jul-17 16:19pm

Dave, I appreciate the response. Since I am new to coding looking up your "separation of concerns" was something I had to do. Since I do not know a lot about coding do you have any examples of creating what you are talking about or possible examples from other people. All my code is doing is creating a temporary form with a picturebox in it so people can enlarge their image. once they are done they can use the escape key and then it will close that temporary form. If there is a better, cleaner way to do this I would love to learn how.

Dave Kreskowiak 24-Jul-17 18:57pm

Simple. A class, and a Form is a class, is responsible for one thing and one thing only.

A class can handle database access to a certain database. A class handles a business object, like a configuration. A class can represent a business process.

In the case of forms, it is responsible for displaying data and input against that data. It it responsible for only the controls on that form, NOTHING MORE.

If the case of your picturebox form, it is a small business process. It shows an image, which you have to pass in somewhere. That form allows some editing of that image, like changing its size and returns that altered image to the caller, your first form.

In all cases, in no way do you let one form handle the events of the controls on another form such as keystrokes and mouse moves and clicks.

You should not be building the picturebox form in the code of the first form. There's no need for that.

Your picturebox form should be shown with ShowDialog, not Show. This makes your first form stop and wait for the picturebox for, shown as a dialog box, to be dismissed before resuming.

I don't have time to build an example and there are tons and tons of articles on passing data between forms all over the web, even here on CP, codeproject pass data between forms[^].