Capturing all keys in Non-GUI applications
CKeyCapturer2 illustrates how to capture all keys inside an application that doesn't implement the standard application frameworks and thus can't use the normal means on getting key events. If you want to capture keys in an application that implements the normal application framework, you can utilize the standard OfferKeyEventL() method implemented in your CCoeControl derived class.
This example implementation makes a window that takes focus and thus gets all key events as any other application taking focus would. Also since it is taking focus, other applications are not receiving any key input. If you just want to capture a few HW keys and let other applications still receive key events you might be better off using the CKeyCapturer implementation.
Article Metadata
Platform Security
Article
Header required:
#include <w32std.h>Library Required:
LIBRARY ws32.libCapability Required:
capability SwEvent
CapturingKeys2.cpp
CKeyCapturer2* CKeyCapturer2::NewL(MKeyCallBack& aObserver)
{
CKeyCapturer2* self = CKeyCapturer2::NewLC(aObserver);
CleanupStack::Pop(self);
return self;
}
CKeyCapturer2* CKeyCapturer2::NewLC(MKeyCallBack& aObserver)
{
CKeyCapturer2* self = new (ELeave) CKeyCapturer2(aObserver);
CleanupStack::PushL(self);
self->ConstructL();
return self;
}
CKeyCapturer2::CKeyCapturer2(MKeyCallBack& aObserver)
:CActive(EPriorityHigh),iObserver(aObserver)
{
}
CKeyCapturer2::~CKeyCapturer2()
{
Cancel();
iWg.Close();
iWsSession.Close();
}
void CKeyCapturer2::ConstructL()
{
User::LeaveIfError(iWsSession.Connect());
CActiveScheduler::Add(this);
iWg=RWindowGroup(iWsSession);
User::LeaveIfError(iWg.Construct((TUint32)&iWg, EFalse));
iWg.SetOrdinalPosition(1, ECoeWinPriorityAlwaysAtFront+2);
iWg.EnableReceiptOfFocus(ETrue);
CApaWindowGroupName* wn=CApaWindowGroupName::NewLC(iWsSession);
wn->SetHidden(EFalse);
wn->SetWindowGroupName(iWg);
CleanupStack::PopAndDestroy();
Listen();
}
void CKeyCapturer2::RunL()
{
if (iStatus == KErrNone)
{
TWsEvent e;
iWsSession.GetEvent(e);
TInt type = e.Type();
switch (type)
{
case EEventKey:
if(iObserver.KeyCapturedL(e))
{
TInt wgId = iWsSession.GetFocusWindowGroup();
iWsSession.SendEventToWindowGroup(wgId, e);
}
break;
case EEventKeyUp:
case EEventKeyDown:
break;
};
}
if (iStatus != KErrCancel)
{
Listen();
}
}
void CKeyCapturer2::DoCancel()
{
iWsSession.EventReadyCancel();
}
void CKeyCapturer2::Listen()
{
iWsSession.EventReady(&iStatus);
SetActive();
}
CapturingKeys2.h
class MKeyCallBack
{
public:
virtual TBool KeyCapturedL(TWsEvent aEvent) = 0;
};
class CKeyCapturer2 : public CActive
{
public:
static CKeyCapturer2* NewL(MKeyCallBack& aObserver);
static CKeyCapturer2* NewLC(MKeyCallBack& aObserver);
virtual ~CKeyCapturer2();
private:
CKeyCapturer2(MKeyCallBack& aObserver);
void ConstructL();
void RunL();
void DoCancel();
void Listen();
private:
MKeyCallBack& iObserver;
RWsSession iWsSession;
RWindowGroup iWg;
};
04 Sep
2009
Some time application need to listen key events in background exe (console exe), to perform some background task, for example capturing long press *. Basically the application that has focus will receive keyevents and other applications will receiving any key input. This article demonstrates the basic step for capturing keyevents using custom class CKeyCapturer2. The code example will helps the developer to implement keylistener.