MCFContextInterface provides possibility to use CF services related to context manipulation:

• Define contexts

• Publish contexts

• Subscribe contexts

• Unsubscribe contexts

• Request contexts Every context source plug-in has a reference to MCFContextInterface by default.

Define context: Before any context can be used in any way it must be defined. Context is defined by a source, type and security policy:

  _LIT( KSource, "Source" );
  _LIT( KType, "Type" );
  _LIT_SECURITY_POLICY_PASS( KPassSec );
  TInt err = iCF.DefineContext( KSource, KType, KPassSec );
  if( err != KErrNone )
    {
    // Handle error...
    }

Publish context: To publish a context the context being publish needs to be defined. To publish a context a new context object must be configured. Context object is configured by setting a source, type and a new value for the context:

  _LIT( KSource, "Source" );
  _LIT( KType, "Type" );
  _LIT( KValue, "NewValue" );
  CCFContextObject* context = CCFContextObject::NewLC();
  context->SetSourceL( KSource );
  context->SetTypeL( KType );
  context->SetValueL( KValue );
  RThread thread;
  CleanupClosePushL( thread );
  TInt err = iCF.PublishContext( *context, thread );
  if( err != KErrNone )
    {
    // Handle error...
    }
  CleanupStack::PopAndDestroy( &thread );
  CleanupStack::PopAndDestroy( context );

It is suggested that only one CCFContextObject* instance is kept as a member variable to save memory.

Subscribe context: To subscribe a context the context being subscribed needs to be defined. A context subscription will not lead to an error even a context which has not been defined is subscribed. Context indications will be received only after the context subscribed is defined. To subscribe a context a new context subscription is made and passed it to Context Framework:

  _LIT( KSource, "Source" );
  _LIT( KType, "Type" );
  CCFContextSubscription* subscription = CCFContextSubscription::NewLC();
  subscription->SetContextSourceL( KSource );
  subscription->SetContextTypeL( KType );
  RThread thread;
  CleanupClosePushL( thread );
  TInt err = iCF.SubscribeContext( *subscription, this, thread );
  if( err != KErrNone )
    {
    // Handle error...
    }
  CleanupStack::PopAndDestroy( &thread );
  CleanupStack::PopAndDestroy( subscription );

It is assumed that 'this' is derived directly from MCFContextSubscriptionListener interface. Context subscription can also be configured more to give more precise indications.

Request context: To request a context the context being requested needs to be defined. Context is requested by defining a context query and passing it to Context Framework:

  _LIT( KSource, "Source" );
  _LIT( KType, "Type" );
  CCFContextQuery* query = CCFContextQuery::NewLC( KSource, KType );
  RThread thread;
  CleanupClosePushL( thread );
  RContextObjectArray results;
  TInt err = iCF.RequestContext( results, *query, thread );
  if( err == KErrNone && results.Count() )
    {
    // Handle request results...
    }
  else
    {
    // Handle error...
    }
  results.ResetAndDestroy();
  CleanupStack::PopAndDestroy( &thread );
  CleanupStack::PopAndDestroy( query );

Remove subscriptions: If a context source plug-in has subscribed contexts it is necessary that also all the contexts will be unsubscribed. Unsubscription can be done by defining a single subscription or to remove all the subscriptions from the particular subscriber:

  _LIT( KSource, "Source" );
  _LIT( KType, "Type" );
  CCFContextSubscription* subscription = CCFContextSubscription::NewLC();
  subscription->SetContextSourceL( KSource );
  subscription->SetContextTypeL( KType );
  iCF.UnsubscribeContext( *subscription, *this );
  CleanupStack::PopAndDestroy( subscription );

 iCF.UnsubscribeContexts( *this );

It is assumed that 'this' is derived directly from MCFContextSubscriptionListener interface.

Since

S60 5.0 -