How do you change page/screen display in c# windows forms without using Close(); and Show(); ?
Close(); and Show(); makes the screen blink and I want it to be fluent. Can I use the menustrip to change screen ?
You can create the new window at exactly the same size and position as the original, and then do a ShowModal on it. When the new window closes, though, you will be back to the original window.
You can make it the same form, but display the controls of each window in different tab pages of a TabControl. I'm not sure offhand how to hide the Tabs which allow the user to change TabPage but I think it can be done; or it might be a good thing to have them there, depending on your requirements.
You can do the Show as you are doing currently, but don't do the Close() of the original form. Instead, when the original form creates the new one, it should subscribe to an event (Activated? or create a special one fired by the new window when it's finished displaying itself) and when it receives that event it calls Close() on itself.
There's three possible ways.
Related
So I'm trying to learn a thing or two about coding with c# and something i find quite annoying is the way to switch between forms.
Lets say for a game you want to go to the options panel and when you click the button to get there it closes that window(form1) and opens a new window(form2) for my app.
It doesn't look very nice having windows opening and closing like that so I'm wondering what i can do in order to make it switch from form1 to form2 without closing form1 and not open form2 in a new window (Everything switched on the main window(form1).
Might sound a bit confusing but hopefully you understand what i mean.
The code I'm using so far to switch between forms:
ChangeOptions optionchanger = new ChangeOptions ();
this.Hide();
optionchanger.Show();
You could add two panels to a single form, each of which contains the controls you would otherwise have added to one of the two forms. Then switch between the panels by changing their visibility or Z-order. This is slightly tricky in the Windows Forms Designer because you'll have to design the two panels, then position them in the same spot on the containing form.
As #ryanyuyu points out, you can set the Dock property to DockStyle.Fill and switch which panel is on top using Control.BringToFront or Control.SendToBack(). This is also a decent way to interact with the two panels in the designer, as you can switch which is on top from a context menu option.
To truly have two forms, your only option is to show a dialog. Hiding your current window is of course optional.
However, you can:
Group all the controls on a given "form" into a Panel or GroupBox, then show/hide the container control.
Put all the controls into UserControls and have an instance of each UserControl on the main form. You can then show/hide the control.
I prefer the second method as it keeps the encapsulation tighter. Since you already have two forms, its easy to convert to user controls.
I want a form to be shown modal every time it is opend. Since I can not change the way it is created and opend. I wondered if it is possible to make the form stay on top from within the forms class.
One opportunity is the TopMost property. This works in general, but if I display the form while the main thread is waiting for it to close, the form will stay on top even if I change the application(to a browser for example). So no matter where I am, the form is still displayed.
Another issue which I came across is that in some cases it is adopted by the parent form which then might block other windows or popup messages.
I was thinking about a hook to the OnLostFocus event to get it on top again, once the focus is lost, but I'm not sure if that is a good idea ...
Any helpful thoughts about it?
Edit
Due to the comments I will extend my description, Here is the real use-case
We are using the Devexpress's SplashScreenManager which is able to show a certain form as a WaitForm. Since the WaitForm is not intended to be shown modal(see on the Support Center), we are looking for a way to do so.
We can not change the way the form is shown, because this is done through the SplashScreenManager. The WaitForm is shown both from the main thread, as well as from certain backgroundworker.
So this is only about an own form of ourselfs, displaying it within our own application.
Use:
TopLevel = true;
This will do exactly what you want; be topmost as long as the main form is shown and hide if the mainform is hidden by another window.
You can set the owner of your splash form to your main form explicitly without using .Show(owner).
splashForm.Owner=mainForm;
splashManager.Show(splashForm);
We did not want the TopMost property since it works on windows level and covers other windows too (for example the browser).
In the end I hooked up on the focus event of the window to make sure the window is always on top.
When Form2 is closed, via it's X button, the Main form is sometimes hidden as well, but not always. Often times the Main form is hidden after initial 'newForm' button click and other times many open-close operations are required before the Main form gets hidden on Form2's closing. Why is this happening? Why is it irregular?
This is a small test code for a larger application I'm working on. In that application a thread continuously reads the network stream and when a particular message is encountered a modal form is displayed. The user can close that modal form or it can be told to close itself by a different network message. In this event, to give the user some time to view the data that the form is displaying I implemented a delayed form closing for that form. When the form is running its delay closing code, another message can come in over the network that will open up a new instance of this form in which case, I observed, that once the timer of the original form runs out, the original form is left displayed until the new instance is closed. Calling Hide in the FormClosing event handler closes the original form if more than one instances of it are running, but it has this side effect of hiding the entire application (the Main form) when the last instance of this form is closed, either by the user or by the delayed closing code. And again, the entire application is not always hidden, but it does happen.
//Main form's 'newForm' button
private void btn_newForm_Click(object sender, EventArgs e)
{
Form2 f = new Form2();
f.ShowDialog();
}
public partial class Form2 : Form
{
private void Form2_FormClosing(object sender, FormClosingEventArgs e)
{
Hide();
}
}
Update (from the application I'm working on):
The problem is shown visually below. The top part of the picture, labeled "A", represents the situation where the first modal dialog (greyed out) was instantiated and it is in the process of being auto closed after 4 seconds have elapsed. The second instance (blue window heading) is active and awaiting input. In the lower part of the picture, labeled "B", the counter to closing of the first instance has completed, yet the first instance remains visible. Adding Hide does not change picture "A" but picture "B" would only be showing the active modal dialog, which is what I want. If Hide is not used and we have the case shown in "B", once the active modal dialog is closed the inactive dialog will disappear together with the active one, but no sooner. At this time my main form will be hidden as well, sometimes.
Your main form doesn't get hidden, it disappears behind another window. The flaw in your code is that for a brief moment none of your windows can get the focus. Your main window can't get the focus, it got disabled by your dialog and won't get re-enabled until the dialog is fully closed. Your dialog can't get the focus, you hide it. So Windows goes looking for another window to give the focus to and can only pick a window owned by another application. Like Visual Studio, nice and big so your main window is well covered by it.
Not sure what you are trying to do, it doesn't make sense to call Hide() since the dialog will close a couple of microseconds later. Just delete the statement.
I am not sure if I am right but maybe you forgot to add e.Cancel = true; to your closing event.
Second, I think using a modal form is only usefull when you expect an action like OK or CANCEL from user, that is where DialogResults comes handy. It sounds strange if this happens time to time not all the time! maybe you can try like this:
//Main form's 'newForm' button
//Define form in your mainform
private Form2 f;
private void btn_newForm_Click(object sender, EventArgs e)
{
if(f != null) { f.Show(); return; }
f = new Form2()
f.FormClosing += delegate { f.Hide(); };
f.Show();
}
I know the topic is quite old, but I recently had to look for answers for this precise question.
Why hiding the (child modal) form instead of closing it ?
I may be wrong, but I think that in some cases, hidding the modal child form instead of closing it is sometimes useful.
For example, I'm using a class that is a custom tree of grids. Think of something like an Excel Document with multiples tables (sheets) and each table can have child tables. A very powerful manner to store datas that can be used by multiple objects and multiple forms at a time.
Now, this "TreeTable_Class" object has an inbuilt custom form that actually shows the content of one of its tables at a time in a GridView, and you can select which table to show by selecting it in a Treeview. You can see here that the "Database Editor" is actually and MDI Form that can load the Form from any TreeTable_Class.
And this is the Form I use to edit the content of a Cell for a given (selected) Table (I've chosen another cell with long text content from another table in this database)
Now, when you choose to close the custom form instead of hiding it, that form will be unaccessible, you can't show it anymore, and you get an exception (no instance of the object) Somewhat, it isn't disposed yet (so the check If MyForm Is Nothing Then... is useless) I know I have to implement the GarbageCollector and dispose the Child Form manually, but it's outside the scope of this topic.
Anyway, my class could use a large amount of memory, of datas, and if I had to rebuilt ALL the contents each time I want to show a new instance of that form, that would be a large amount of workload in my application. That's why I have chosen to hide the form instead of closing it until the main application exits or when a specific CloseFormAndDispose() method is explicitly called, either by the program, or if I make this option available for the user via an user interface.
Workaround try :
This is the workaround I've found to override the "form replaced by another because none of the parent/child ones could be retrieved" :
Sorry, I'm in VB.. but you can use a tool to convert this to C#, or do it manually, it's pretty simple..
// This is the child, a Cell Editor that can edit the content of a Cell.
Protected WithEvents _CellEditor As CellEditor_Form = Nothing
This Editor form is a member of TreeTable_Form, a form that can actually show and edit the content of the whole Database File (a single file)
And this TreeTable_Form class contains a routine that handles CellEditor closing event
Public Partial Class TreeTable_Form
// Sorry. The "WithEvents" in C# is a litte bit complex to me... So, in VB :
Protected WithEvents _CellEditor As CellEditor_Form = Nothing
// ...
// CellEditor handling method (I used a Code converter...) :
// The original VB declaration is :
// Protected Sub RecallFormAfterCellEditorHidden() Handles _CellEditor.Closed
// You'll have to write specific Event handler for _CellEditor object declared above...
protected void RecallFocusAfterCellEditorHidden()
{
Application.DoEvents();
this.Focus();
}
End Class
This tiny protected void RecallFormAfterCellEditorHidden() method in your Class (if you are using a class that contains Forms) or in your Main From, assuming that your main form contains the child forms (dialogs) will try to force the focus on your Application or MainForm...
By the way, TreeTable_Form is actually a component of TreeTable_Class. The later is an object that can be used anywhere you want. In a Main Form Application, in another Class, in a dialog, anywhere... and could be passed by reference to share its contents between several items. And this TreeTable_Class contains a RecallFocusAfterTreeViewerHidden() method that handles the closing of that form. That means, the Form or Application that actually uses the class will get the focus each time you close the its child Form. I've made it that way to get an object that could be used anywhere
We still get problems !
However, this method will make your application flicker a bit each time you close your child dialog, and doesn't succeed at 100% ! Sometimes, my parent form still disappear from screen and gets struck behind another window. Alt+TAB wont helt either. But this happens less than without this method trick. I don't have any better answer at this time, still searching... I'll come back here if I find out how. I'm using this custom made application in my work to write memos during meetings for example, and produce PV (procès verbal - french sorry) in PDF or DOCx on the fly...
And I'm sorry, I'm in VB, not C#. Hope this helps a little, until we find a better workaround for this...
I was wondering if there are any gotchas for making a form completely transparent (as opposed to hiding it). For instance, I know that these are things that got my by surprise when hiding a form:
If a form is hidden, you cannot interact with its controls (can't add HTML to a webbrowser control, can't push a button, etc.)
Changing the WindowState (minimized, maximized, etc) of a window while it is hidden will cause the window to appear outside the scope of your work area when the form is shown again.
Has anybody run into similar problems (or completely different ones!) while using a form with opacity set to 0 (completely transparent)?
If you don't need the form anymore, hide it.
But if you still have a task or timers running in the form you want to keep, or you want to keep the user's input, then you'd do good to set the opacity to 0%.
This is what I do when I want a form to be hidden, but still active:
frmMain.Opacity = 0; // To make it invisible.
frmMain.VisibleInTaskbar = false; // To make the taskbar entry of the form disappear, and to make sure that the WindowState isn't changed.
frmMain.Enabled = false; // To make sure the user doesn't type something in the form, or presses a button (by pressing enter) by accident.
From the up votes for my comment, I guess I'll submit it as an answer. I would discourage using Form.Opacity = 0. Even though you can disable the form to prevent accidental interaction, I would think the transparent form would overlay other windows and confuse the user as to why he can't interact with windows behind your transparent one.
As for the gotcha's for Form.Hide(), I typically queue form responses so that when the form returns into view (or visibility), it goes through the queue to process actions (i.e. changing FormState). Changing the form while it's hidden can also really confuse the user.
Thinking about this for an About dialog but I'm sure it's applicable in other places (say a find box)
Sorry if this is a dupe, but I couldn't find this or how to articulate the last part about it only being on top of the parent. How do you make a form that is always on top of the parent form, but is non-modal, but doesn't cover up other apps?
Try this to open your dialog:
FindDialog fd = new FindDialog();
fd.Show(this);
The key is to assign dialog's owner.
Not sure exactly what you mean; Form.ShowDialog is only modal with respect to the parent, not the application, unless the application is single threaded.
For example, I made an app to test this which was organized like the following:
mainform:
2 buttons, each of which begins a thread that creates a frmDialog1 and calls ShowDialog
frmDialog1:
single button which creates a frmDialog2 and calls ShowDialog on it.
frmDialog2:
does nothing (ie. blank)
when they were all running I could access/drag mainform. I could also do the same with frmDialog1 (both versions) only if I hadn't clicked the button that shows dialog 2.