chxavactivewatcher.cpp

来自「symbian 下的helix player源代码」· C++ 代码 · 共 143 行

/************************************************************************
 * chxavactivewatcher.cpp
 * ----------------------
 *
 * Synopsis:
 *
 * Implementation of base class for classes that request active object
 * event notification from system services.
 *
 *
 *
 * (c) 1995-2003 RealNetworks, Inc. Patents pending. All rights reserved.
 *
 ************************************************************************/ 

// Symbian includes...

// Helix includes...
#include "hxassert.h"

// Includes from this project...
#include "hxsym_debug.h"
#include "chxavmisc.h"
#include "chxavactivewatcher.h"

///////////////////////////////////
// ctor
CHXAvActiveWatcher::CHXAvActiveWatcher()
: m_bKeepWatching(false)
, m_msForwardEventDelay(0)
{
}

///////////////////////////////////
// dtor
CHXAvActiveWatcher::~CHXAvActiveWatcher()
{
    // derived classes must call StopWatching() (recall there is a this pointer adjustment during destruct)
    HX_ASSERT(!m_spWatchObject->IsActive());
}

///////////////////////////////////
//
void CHXAvActiveWatcher::BaseConstructL(TInt activePriority)
{
    // initialize active object for receiving system event notifications
    m_spWatchObject =  new CHXAvActiveDisp<CHXAvActiveWatcher>(this, &CHXAvActiveWatcher::OnEvent, &CHXAvActiveWatcher::OnCancelWatch);
    m_spWatchObject->SetPriority(activePriority);
    CActiveScheduler::Add(m_spWatchObject.raw_ptr());

    // see OnEvent()
    m_cbFowardEvent.ConstructL(MakeCommand(this, &CHXAvActiveWatcher::ForwardEvent));
}

///////////////////////////////////
// active object cancel
void CHXAvActiveWatcher::OnCancelWatch(TInt status)
{
    DPRINTF(SYMP_INFO, ("CHXAvActiveWatcher::OnCancelWatch(): status = %d\n", status));
    m_bKeepWatching = false;

    // derived: cancel request from system system service provider
    DoCancelRequest(m_spWatchObject);
}

////////////////////////////////////////////////////////
// foward event notification to event handler
void CHXAvActiveWatcher::ForwardEvent()
{
    // set watch before executing handler so events are not missed
    if(m_bKeepWatching)
    {
	WatchForNextEvent();
    }

    if(m_spEventHandler)
    {
	m_spEventHandler->Execute();
    }
}
////////////////////////////////////////////////////////
// event notication from system
void CHXAvActiveWatcher::OnEvent(TInt status)
{
    DPRINTF(SYMP_INFO, ("CHXAvActiveWatcher::OnEvent(): status = %d; keep watching = %s\n", status, dbg::Bool(m_bKeepWatching)));
    if(KErrNone == status)
    {
	if( m_msForwardEventDelay != 0 )
        {
            //
            // delay notification for this event to prevent execessive event
            // notifications; this is helpful for events such as filesystem 
            // events, where many events may be generated in rapid succession
            // (e.g.,a group of files are being created/deleted/moved)
            //
            m_cbFowardEvent.Set(m_msForwardEventDelay);
        }
        else
        {
            ForwardEvent();
        }
    }
}

////////////////////////////////////////////////////////
// watch all events from here on
void CHXAvActiveWatcher::StartWatching()
{
    m_bKeepWatching = true;

    // start watching if not watching already
    if (!m_spWatchObject->IsActive())
    {
	WatchForNextEvent();
    }
}


////////////////////////////////////////////////////////
//
void CHXAvActiveWatcher::WatchForNextEvent()
{
    HX_ASSERT(!m_spWatchObject->IsActive());

    // derived: request event notification from some system service
    DoIssueRequest(m_spWatchObject);

    m_spWatchObject->Activate();
}

////////////////////////////////////////////////////////
//
void CHXAvActiveWatcher::StopWatching()
{
    m_bKeepWatching = false;
    if( m_spWatchObject && m_spWatchObject->IsActive() )
    {
	m_spWatchObject->Cancel();
    }
}