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Subject Author Date
single instance application Tim Wallace 03-22-2006
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Posted by Tim Wallace on March 22, 2006, 11:43 pm
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 I have an application written in C# for Smartphone. I was (obviously)
mistaken in thinking that if my app is running and I press the Home key and
then click the icon to start my app again, that the OS would switch to the
already-running application. How does one accomplish this singleton on a
Smartphone (mutex, something else)? This is unknown territory to me on
Smartphone.

Tim



Posted by riki on March 22, 2006, 11:52 pm
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 Tim Wallace wrote:
> I have an application written in C# for Smartphone. I was (obviously)
> mistaken in thinking that if my app is running and I press the Home key and
> then click the icon to start my app again, that the OS would switch to the
> already-running application. How does one accomplish this singleton on a
> Smartphone (mutex, something else)? This is unknown territory to me on
> Smartphone.

the c++ wizard uses a names mutex to detect previous instances, then
switches to the old instance using SetForegroundWindow();

riki

----
The history of liberty is a history of the limitation of governmental
power, not the increase of it.-- Woodrow Wilson, 1912
By Night:
ThemeChanger for Smartphone : http://homepages.inspire.net.nz/~gambit/
AbstractStart for Smartphone :
http://homepages.inspire.net.nz/~gambit/AbstractStart/
Latest Betas have WM5 layout and speed dial support

Posted by Tim Wallace on March 23, 2006, 12:23 am
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Riki:

Thanks for your reply, but I've coded this app in C#. I don't see how the
C++ wizard applies. Could you explain further?

Tim

> Tim Wallace wrote:
>> I have an application written in C# for Smartphone. I was (obviously)
>> mistaken in thinking that if my app is running and I press the Home key
>> and then click the icon to start my app again, that the OS would switch
>> to the already-running application. How does one accomplish this
>> singleton on a Smartphone (mutex, something else)? This is unknown
>> territory to me on Smartphone.
>
> the c++ wizard uses a names mutex to detect previous instances, then
> switches to the old instance using SetForegroundWindow();
>
> riki
>
> ----
> The history of liberty is a history of the limitation of governmental
> power, not the increase of it.-- Woodrow Wilson, 1912
> By Night:
> ThemeChanger for Smartphone : http://homepages.inspire.net.nz/~gambit/
> AbstractStart for Smartphone :
> http://homepages.inspire.net.nz/~gambit/AbstractStart/
> Latest Betas have WM5 layout and speed dial support



Posted by riki on March 23, 2006, 12:29 am
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Tim Wallace wrote:
> Riki:
>
> Thanks for your reply, but I've coded this app in C#. I don't see how the
> C++ wizard applies. Could you explain further?

it doesn't directly apply, but you can use the same method. I'm not a c#
guru, but you should be able to create a named mutex to detect previous
instances, and you should be able to do something similar to a
SetForegroundWindow(FindWindow(L"apptitle"))

riki


----
To know the road ahead, ask those coming back.-- Chinese proverb
By Night:
ThemeChanger for Smartphone : http://homepages.inspire.net.nz/~gambit/
AbstractStart for Smartphone :
http://homepages.inspire.net.nz/~gambit/AbstractStart/
Latest Betas have WM5 layout and speed dial support

Posted by Tom Moon on April 7, 2006, 4:21 pm
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Here's the C++ implementation. I'm sure it's easy to re-interpret this
in C#
The C++ Wizard adds a few more bells and whistles to make the Previous
App Instance check more robust. This method works well enough.

// TRUE means we found a previous instance of this program running
// FALSE means we are the only instance running on the system
BOOL IsPrevInstance(void)
{
HWND hwnd;
BOOL fIsPrevInstance = FALSE;

// Create a named event
g_hSingleEvent = CreateEvent(NULL, TRUE, FALSE, g_szClassName);
DWORD err = GetLastError();
if(g_hSingleEvent == NULL)
{
// bad ERROR; we should quit!
return TRUE;
}
// If the event already existed, that means there's
// another copy of our app already running
if(err == ERROR_ALREADY_EXISTS)
{
// We found the named event; now try to find the
// other application window by that name
hwnd = FindWindow(g_szClassName, NULL);
if(NULL != hwnd)
SetForegroundWindow((HWND)((UINT_PTR)hwnd | 0x01));
CloseHandle(g_hSingleEvent);
// we should quit; another instance found!
fIsPrevInstance = TRUE;
}//end if(ALREADY_EXISTS)

return fIsPrevInstance;
}// end IsPrevInstance

-J Tom Moon


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