Creating a handler application for a MIME type using Symbian C++
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Overview
It is sometimes necessary to launch a handler application (such as a viewer) for files selected, for example, through the File manager. This code snippet demonstrates how to write a handler for TeX files (MIME type: application/x-tex).
Note: If the MIME type of the file is not known, the handler application cannot be launched. In this case, you need to write a data recognizer that identifies the MIME type of the file. For more information about implementing a data recognizer, see Creating a recognizer plug-in for a MIME type on Symbian.
Resource file: CTeXHandler_reg.rss
The data handler is registered to handle that particular MIME type by adding a datatype_list section to the application's reg.rss file. The section lists the MIME types that the application is able to handle, and the priority of support for each MIME type. The priority can be one of the following four values:
- EDataTypePriorityHigh
- EDataTypePriorityNormal
- EDataTypePriorityLow
- EDataTypePriorityLastResort
Symbian OS launches the application that has the highest priority support for the data type in question.
Here is the relevant part of the reg.rss file:
RESOURCE APP_REGISTRATION_INFO
{
app_file = "CTeXHandler";
localisable_resource_file = qtn_loc_resource_file;
localisable_resource_id = R_LOCALISABLE_APP_INFO;
embeddability = KAppEmbeddable;
datatype_list =
{
DATATYPE
{
priority = EDataTypePriorityHigh;
type = "application/x-tex";
}
};
}
Header file: CTeXHandlerDocument.h
#include <akndoc.h> // CAknDocument
class CTeXHandlerDocument : public CAknDocument
{
// ...
public: // Functions from base classes
/**
* From CAknDocument.
* Create a CTeXHandlerAppUI object and return a pointer to it.
* The object returned is owned by the Uikon framework.
* @return a pointer to the created instance of AppUI.
*/
CEikAppUi* CreateAppUiL();
/**
* From CAknDocument.
* Opens a file.
*/
void OpenFileL(CFileStore*& aFileStore, RFile& aFile);
private: // Data
CEikAppUi* iAppUI;
};
Source file: CTeXHandlerDocument.cpp
CEikAppUi* CTeXHandlerDocument::CreateAppUiL()
{
// Create the application user interface, and return a pointer to it;
// the framework takes ownership of this object
iAppUI = new (ELeave) CTeXHandlerAppUI();
return iAppUI;
}
void CTeXHandlerDocument::OpenFileL(CFileStore*& aFileStore, RFile& aFile)
{
// Store the filename in a local variable
TFileName filename;
aFile.Name(filename);
// Store the first few characters of the file contents in a local variable
const TInt KCharsToRead = 20;
TBuf8<KCharsToRead> contents;
User::LeaveIfError(aFile.Read(contents, KCharsToRead));
// Delegate file handling to the application UI
CTeXHandlerAppUI *appUI = static_cast<CTeXHandlerAppUI*>(iAppUI);
appUI->SetFileData(filename, contents);
}
Header file: CTeXHandlerAppUI.h
#include <aknappui.h>
class CTeXHandlerAppUI : public CAknAppUi
{
// ...
public: // New functions
/**
* Handles the file.
*/
void SetFileData(TDes& aFileName, TDes8& aData);
private: // Data
/**
* The application view.
* Owned by CTeXHandlerAppUI.
*/
CTeXHandlerAppView* iAppView;
};
Source file: CTeXHandlerAppUI.cpp
void CTeXHandlerAppUI::SetFileData(TDes& aFileName, TDes8& aData)
{
if (iAppView)
{
iAppView->SetFileData(aFileName, aData);
}
}
Header file: CTeXHandlerAppView.h
#include <coecntrl.h>
class CTeXHandlerAppView : public CCoeControl
{
// ...
public: // New functions
/**
* Handles the file.
*/
void SetFileData(TDes& aFileName, TDes8& aData);
// ...
};
Source file: CTeXHandlerAppView.cpp
void CTeXHandlerAppView::SetFileData(TDes& aFileName, TDes8& aData)
{
// Handle the TeX file: Draw its contents onto the screen etc.
}
Postconditions
A handler for TeX files is implemented. If the file of type application/x-tex is opened for example from the File manager, the CTeXHandlerDocument::OpenFileL() method is called. It delegates file handling to the view object: CTeXHandlerAppView::SetFileData().
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