In the project source, I detect a previous instance of my app, and open it then terminate the new instance.
Remember, I do this in the project source.
The application has a main form that can open a second modal form. If the second, modal, form is not open when the app is minimized (or the user switches to another application) it works fine.
The old main form is opened and the new instance is terminated. However, if the second modal form is minimized, its parent main form is also minimized. That's good UI behavior.
The problem exists when attempting to restore the modal form by a new instance. I can't seem to get the modal form to restore.
I can restore the main form, however the modal form still has focus, but is hidden.
This prevents any user action on the now visible main form. From the user's point of view, the app is hung.
The modal form's caption does not change, so it's easy to get its handle.
The app has a DataModule, which is created first. I do all the duplicate app testing in the project source after the DM is created, but before any other forms are, and well before Application.Run.
That assures that the handles I acquire come from the existing app.
I've tried:
PreviousHandle := FindWindow(nil, PAnsiChar('Form Editor'))
ShowWindow(PreviousHandle,SW_RESTORE);
ShowWindow(PreviousHandle,SW_NORMAL);
BringWindowToTop(PreviousHandle);
The best I've gotten out of variations of this is restoring the main form.
When the handle is for the modal form, it sometimes shows in the lower left as a minimized form.
I say sometimes because I've tried so many variations of the above that I don't remember exactly how this code sample behaved.
All I know is, whatever I've tried from the project source did not restore the modal form, so I tried sending a custom Windows Message to the modal form.
I know the message arrived and the message handler caught it. Example:
if not PostMessage(PreviousHandle,WM_RESTORE_FORM,PreviousHandle,0) then
ShowMessage('Can''t automatically show the Form program. '+
'Please click the taskbar icon.');
Here's what the message handler looks like. It is in the Modal Form. As you can see, I pass the form's handle as a Message param. I've verified that it arrives.
Here's the code in a TApplicationEvents OnMessage event:
procedure TfrmDisplayForm.ApplicationEvents1Message(var Msg: tagMSG;
var Handled: Boolean);
var
oldHwnd : THandle;
begin
if Msg.message = WM_RESTORE_ACORD then
begin
oldHwnd := Msg.lParam;
if ForceForegroundWindow(OldHwnd) then ShowMessage('true') else ShowMessage('False');
Handled := True;
end;
end;
Here's the function that is called. However, I've tried various ShowWindows(...) combinations with no luck. Actually, this function didn't do the trick either.
function TfrmDisplayForm.ForceForegroundWindow(hWnd: THandle): BOOL;
var
hCurWnd: THandle;
begin
{credit Peter Below}
hCurWnd := GetForegroundWindow;
AttachThreadInput(GetWindowThreadProcessId(hCurWnd, nil),
GetCurrentThreadId, True);
Result := SetForegroundWindow(hWnd);
AttachThreadInput(GetWindowThreadProcessId(hCurWnd, nil),
GetCurrentThreadId, False);
end;
I've been working on this for a couple of days, and don't know what I'm doing wrong.
Question: How can I restore the modal form? It must be possible because it restores perfectly when the taskbar icon is clicked.
Don't try to restore individual forms instead use TApplication.Restore
Calling TApplication.Restore will restore all of the application windows to the state before the whole application was minimized same as clicking on TaskBar icon of the application.
PS: I also hope you are not allowing users to minimize individual Modal forms. Or you may also run into a problem where application seems to be stuck.
Related
Update: Manually losing the form and re-opening it also causes editing to be allowed, please see Step 4 below and "Additional Notes" section below. Thanks!
An MS-Access 2007 database that I have simplified a great deal during troubleshooting still has the same problem:
Restart Access and open the database
The autoexec calls a vba function that initializes some TempVars, then opens a form with: `DoCmd.OpenForm FormName:="MainEditor"
All Bound and Un-Bound Text Boxes and Combo Boxes display their data
correctly, but NONE of them can be edited. Keystrokes are ignored, pull-downs on Combo Boxes display lists of choices correctly but no choice can be selected.
Change the form's view to Design View, then immediately change it back to Form View. Alternatively, manually close the Form and then re-open it.
All the controls continue to display their data correctly, but now ALL of
them can be edited normally.
After changing to Design View and back to Form View, the Form is editable normally until Access is shut down and restarted.
Additional Notes:
I tried adding a DoCmd.Close and a DoCmd.FormOpen immediately after the original DoCmd.FormOpen in the startup function called by the Autoexec macro, but the Form remained unable to accept edits. Manually closing the form, and then manually re-opening it, seems to work every time. Is there any chance that Access needs a delay to process before opening the form, and manually doing the close/open cycle provides that time window?
Here's some background:
The Table has a primary index, 4 other indexes, and one-to-many relations to 7 other tables.
The Form's Record Source is the Table, and Allow Edits = Yes.
All the controls on the Form are set: Enabled = Yes, and Locked = No.
There are no sub-forms, only the one Form.
This isn't much to go on. If you ask for further specifics I'd be glad to provide them.
Thank you. Dave
Instead of using an Autoexec macro, specify a startup form.
I have two delphi forms; frmHome and frmStats. There is a button on the main form (frmHome) and when you click on it it takes you to frmStats.
On btn click in frmHome:
frmStats.ShowModal;
Hide;
This works fine but on frmStats there is also a button that I would like to take the user back to the main form when clicked on. The problem is I get error messages.
If I make reference to the form like this I get the error message "cannot make visable window modal"
implementation
uses frmHome_u;
However if I make reference like this, then i get the message "circular unit reference"
interface
uses {a bunch of uses} , frmHome_u;
On btn click in frmStats:
frmHome.ShowModal;
Hide;
How do I do this?
Modal forms have owners. These owning forms are disabled when the modal form is shown. A form is always shown above its owner.
You are trying to make form1 be the owner of form2 and then in turn have form2 own form1. That circular ownership is not allowed. It would imply that both windows would be disabled, and each window on top of the other.
What you need to do is to close the modal form. Replace
frmHome.ShowModal;
Hide;
with
ModalResult := mrOK;
If you want both forms to be visible and enabled at the same time, then you must not show them modally.
If I understand what you are trying to do then this should work just fine.
frmStats.Enabled := True;
frmStats.Show;
Enabled := False;
Hide;
And you have the reciprocal code in the other form.
Because the other form is disabled, it can not be brought into focus until you enable it.
EDIT
If the users closes FrmStats and FrmHome is the mainform then you must enable it in the onclose event.
Is there some method of detecting if there is a modal form showing in my VB6 application.
I want to show another form modally if there is a modal form showing and modeless if there isn't a modal form showing.
I know I can do some error handling to detect this and show modally if the error occurs:
Public Sub ShowFormModeless(frm As Form, Optional ownerForm As Form = Nothing)
On Error GoTo ShowModal
Call frm.Show(, ownerForm)
Exit Sub
ShowModal:
Call frm.Show(vbModal, ownerForm)
End Sub
But I want to be able to detect this without the error being thrown.
Try checking App.NonModalAllowed. Note that this property does not detect modal forms being shown from other (than current module) projects, i.e. if your application consists of main executable and several ActiveX dlls each of these projects will have a separate App object and Forms collection.
The result is that if a dll is showing a modal form only its own project's App.NonModalAllowed is flagged. So once again, App.NonModalAllowed is not a process-wide flag but a per project one.
Note that this flag tracks VB6 only forms, so if you are using API dialogs (open/save file, color picker, etc) this does not enter VB6 runtime's modal loop, so nothing is flagged.
If you application is a single exe then using this flag works as expected.
Is there a property that tells if a form is deactivated by other form ShowModal procedure ?
EDIT :
My program has a tray icon that brings to front the main form when it's clicked. I want to disable this when another window is shown in modal state. Because not doing so the main form (which is disable) will cover the modal form and completly block my program.
This behaviour is to be expected. When a modal form is shown, the other forms are disabled. You don't need to disable anything at all, the framework already handles it all for you. The beep is sounding because you are attempting to interact with a disabled form.
If you want to be notified when your window has been disabled, for any reason, not just because a modal form has been shown, listen to the WM_ENABLE message. To test whether or not your main form has been disabled. Do that by calling the IsWindowEnabled Win32 function.
Having said that I feel that it is likely you've not diagnosed the issue correctly. It sounds like you might be suffering from window ownership problems, which are common in Delphi 6. Or perhaps you are attempting to restore the application incorrectly from your notification icon code. Use Application.BringToFront for that.
The VCL's handling of modal dialogs seem very mixed up. When you show a system provided modal dialog, e.g. MessageBox, windows are disabled whether or not they are visible. However, the VCL only disables visible windows when ShowModal is called. What's more, you cannot use Enabled to test whether or not the window is disabled, you must use the IsWindowEnabled Win32 function.
You can test Application.ModalLevel at any point in time to find out if there's a modal form. E.g.:
if Application.ModalLevel = 0 then
MainForm.Visible := True;
Note that non-TCustomForm descendants will not set modal level, API dialogs like a file open dialog or MessageBox for instance. If there's a possibility of such a thing, you might surround code that runs those dialogs with ModalStarted and ModalFinished.
It doesn't seem necessary in your case, but if you somehow need to be notified that a form/dialog is going modal, you can attach a handler to Application.OnModalBegin and Application.OnModalEnd events. You can use an TApplicationEvents component for that.
Going "back" from a form doesn't take me to the previous form but back to the main form. What am I doing wrong? Here's more detail:
I have a Command that takes you from the main form of my app to a "human setup" form. From that form if you click on a certain multibutton I go to another form (MaintenanceLevel) like this:
protected void onHumanSetup_MultiButtonMaintenanceAction(Component c, ActionEvent event) {
// Invoke the next level of form
showForm("MaintenanceLevel", null);
}
In the "MaintenanceLevel" form I have an Action set to Back, but when I click the menu bar to go back I end up back on the main-form and not the "human setup" where I want to be.
Edit:
Things have got a little worse!! Now when I go back in to view the Commands for my MaintenanceLevel form it's empty: it's forgetting the command I've entered :(
Here is my command setting for MaintenanceLevel form:
You don't need to define a back command. Remove it. Codename One automatically creates back commands for you.
The usage for this option is when you create a Button and place it within the form, then you want it to behave as a back button effectively (e.g. cancel button).