Publish及Subscribe：使用RProperty进行subscribe操作
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详细描述
下列代码片段演示了如何使用RProperty来订阅用户使用Symbian IPC发布及订阅机制定义的属性。下列步骤用来订阅并接收属性更新状态。
- 使用RProperty::Attach()标注需要的属性，然后调用RProperty::Subscribe()订阅
- 通过TRequestStatus信号通知RProperty::Subscribe()完成。
- 调用RProperty::Get()获得更新后的属性值
- 通过RProperty::Subscribe重新提交请求来监听属性变化
- 最终调用RProperty::Cancel来取消订阅，以及通过RProperty::Close
Archived:Using RProperty for publishing中的代码片段演示了用户定义属性如何被发布，这些属性定义将通过ExampleProperties.h在发布者和订阅者之间共享。
#ifndef EXAMPLEPROPERTIES_H_
#define EXAMPLEPROPERTIES_H_
const TInt KMaxStrLen = 10;
const TUid KExampleProperty = {0xED1917A8};
enum TExamplePropertyKeys { EIntProperty, EStrProperty };
#endif /*EXAMPLEPROPERTIES_H_*/
This snippet can be self-signed.
MMP文件
需要下列链接库
LIBRARY euser.lib
前言
发布者或订阅者线程都可以调用RProperty::Define()来定义属性。用户定义的属性将一直保存到操作系统重启或被删除。
TInt ret=RProperty::Define(KExampleProperty,EIntProperty,RProperty::EInt);
if (ret != KErrAlreadyExists)
{
User::LeaveIfError(ret);
}
ret= RProperty::Define(KExampleProperty,EStrProperty,RProperty::EByteArray,KMaxStrLen);
if (ret != KErrAlreadyExists)
{
User::LeaveIfError(ret);
}
头文件
#ifndef EXAMPLESUBSCRIBER_H_
#define EXAMPLESUBSCRIBER_H_
// INCLUDES
#include <e32base.h>
#include <e32property.h>
#include "exampleproperties.h"
class MExampleSubscriberObserver
{
public:
virtual void IntPropertyUpdatedL(TInt aValue) = 0;
virtual void StrPropertyUpdatedL(TDes& aValue) = 0;
};
class CExampleSubscriber : public CActive
{
enum {EPriority=0};
public:
static CExampleSubscriber* NewL( const TUid aUid,
const TUint32 aKey,
MExampleSubscriberObserver& aNotifier );
virtual ~CExampleSubscriber();
private:
CExampleSubscriber( const TUid aUid, const TUint32 aKey,
MExampleSubscriberObserver& aNotifier );
void ConstructL();
void RunL();
void DoCancel();
private:
RProperty iProperty;
const TUid iUid;
const TUint32 iKey;
MExampleSubscriberObserver& iObserver;
};
#endif /*EXAMPLESUBSCRIBER_H_*/
源文件
#include "ExampleSubscriber.h"
CExampleSubscriber::CExampleSubscriber(
const TUid aUid, const TUint32 aKey,
MExampleSubscriberObserver& aObserver )
: CActive(EPriority), iUid( aUid ),
iKey( aKey ), iObserver( aObserver)
{
}
CExampleSubscriber* CExampleSubscriber::NewL( const TUid aUid, const TUint32 aKey,
MExampleSubscriberObserver& aObserver )
{
CExampleSubscriber* self=
new(ELeave) CExampleSubscriber( aUid, aKey, aObserver );
CleanupStack::PushL(self);
self->ConstructL();
CleanupStack::Pop(self);
return self;
}
void CExampleSubscriber::ConstructL()
{
User::LeaveIfError( iProperty.Attach( iUid, iKey ) );
CActiveScheduler::Add(this);
// initial subscription and process current property value
RunL();
}
CExampleSubscriber::~CExampleSubscriber()
{
Cancel();
iProperty.Close();
}
void CExampleSubscriber::DoCancel()
{
iProperty.Cancel();
}
void CExampleSubscriber::RunL()
{
// resubscribe before processing new value to prevent missing updates
iProperty.Subscribe( iStatus );
SetActive();
TInt intValue;
TBuf<KMaxStrLen> strValue;
switch( iKey )
{
case EIntProperty:
// Int property updated, get new value
//see also: RProperty::Get(KExampleProperty,EIntProperty,intValue);
if( iProperty.Get( intValue ) == KErrNotFound )
{
// Int property deleted, do necessary actions here...
}
else
{
// use new value ...
iObserver.IntPropertyUpdatedL(intValue);
}
break;
case EStrProperty:
// Int property updated, get new value
//see also: RProperty::Get(KExampleProperty,EStrProperty,strValue);
if( iProperty.Get( strValue ) == KErrNotFound )
{
// Str property deleted, do necessary actions here...
}
else
{
// use new value ...
iObserver.StrPropertyUpdatedL(strValue);
}
break;
default:
break;
}
}
// End of File
使用CExampleSubscriber类
- 在头文件里:
#include "examplesubscriber.h"
class CPropertyExampleAppUi : public CAknAppUi, MExampleSubscriberObserver
{
//...
public:
void IntPropertyUpdatedL(TInt aValue);
void StrPropertyUpdatedL(TDes& aValue);
//...
CExampleSubscriber* iIntSubscriber;
CExampleSubscriber* iStrSubscriber;
};
- In the source file:
void CPropertyExampleAppUi::ConstructL()
{
//...
iIntSubscriber = CExampleSubscriber::NewL(KExampleProperty,EIntProperty,*this);
iStrSubscriber = CExampleSubscriber::NewL(KExampleProperty,EStrProperty,*this);
}
CPropertyExampleAppUi::~CPropertyExampleAppUi()
{
//...
delete iIntSubscriber;
delete iStrSubscriber;
}
void CPropertyExampleAppUi::IntPropertyUpdatedL(TInt aValue)
{
//do something with the updated property
}
void CPropertyExampleAppUi::StrPropertyUpdatedL(TDes& aValue)
{
//do something with the updated property
}
后记
使用RProperty来订阅两个示例属性
如果订阅线程定义了属性，那么也可以使用RProperty::Delete()来删除掉。
TInt err(KErrNone);
err = RProperty::Delete(KExampleProperty,EIntProperty);
if (err != KErrNotFound)
{
User::LeaveIfError(err);
}
err = RProperty::Delete(KExampleProperty,EStrProperty);
if (err != KErrNotFound)
{
User::LeaveIfError(err);
}
当属性都被删除掉后，任何未完成的订阅将被告知KErrNotFound完成
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