Archived:Storing application settings in Symbian C++
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Contents |
Overview
The following example shows how to handle application settings. Settings are stored into the private folder of the application.
MMP file
The following capabilities and libraries are required:
CAPABILITY NONE
LIBRARY efsrv.lib
LIBRARY estor.lib
Header file, CSettingsData.h
Settings data class for storing/reading settings data from the stream.
#include <e32base.h>
class CSettingsData : public CBase
{
public:
static CSettingsData* NewL();
static CSettingsData* NewLC();
virtual ~CSettingsData();
// Loads itself from stream.
void LoadL(RReadStream& aStream);
// Saves itself to stream.
void SaveL(RWriteStream& aStream) const;
// Using default values (e.g. in first time)
void SetDefaultValues();
inline TBuf<100>& Text() { return iText; }
inline TInt& Enumeration() { return iEnumeration; }
private:
CSettingsData();
void ConstructL();
public:
TBuf<100> iText; //Data for text field
TInt iEnumeration; // Data for enumerated text field
Source file, CSettingsData.cpp
CSettingsData *CSettingsData::NewL()
{
CSettingsData *self = CSettingsData::NewLC();
CleanupStack::Pop(self);
return self;
}
CSettingsData *CSettingsData::NewLC()
{
CSettingsData *self = new (ELeave) CSettingsData();
CleanupStack::PushL(self);
self->ConstructL();
return self;
}
CSettingsData::~CSettingsData()
{
}
CSettingsData::CSettingsData()
{
}
void CSettingsData::SetDefaultValues()
{
// TODO: Set default values of your setting
iEnumeration = 1000;
}
void CSettingsData::ConstructL()
{
}
// Reading setting data from stream
void CSettingsData::LoadL(RReadStream& aStream)
{
aStream >> iText;
iEnumeration = aStream.ReadInt32L();
}
// Storing setting data into stream
void CSettingsData::SaveL(RWriteStream& aStream) const
{
aStream << iText;
aStream.WriteInt32L(iEnumeration);
}
Header file, CMyAppUi.h
Application class that reads settings on construction and stores them on exit.
#include <aknviewappui.h>
#include "CSettingsData.h"
class CMyAppUi : public CAknViewAppUi
{
public:
void ConstructL();
CSettingExampleAppUi();
~CSettingExampleAppUi();
public: // from CEikAppUi
void HandleCommandL(TInt aCommand);
private:
void InternalizeSettingsDataL();
void ExternalizeSettingsDataL() const;
private:
CSettingsData* iData; // Pointer to settings data
TFileName iSettingsFile;
};
Source file, CMyAppUi.cpp
void CMyAppUi::ConstructL()
{
BaseConstructL(EAknEnableSkin);
// Create private path
RFs& fsSession = iEikonEnv->FsSession();
User::LeaveIfError(fsSession.CreatePrivatePath( EDriveC ) );
User::LeaveIfError(fsSession.PrivatePath(iSettingsFile));
iSettingsFile += KSettingsFile;
// Construct the data object the settings list will use
iData = CSettingsData::NewL();
// Read settings from stream
InternalizeSettingsDataL();
// TODO: Construct and activate the app view as well
}
// Handle menu commands
void CMyAppUi::HandleCommandL(TInt aCommand)
{
switch(aCommand)
{
case EEikCmdExit:
case EAknSoftkeyExit:
{
// Store setting data on application exit
ExternalizeSettingsDataL();
Exit();
break;
}
default:
break;
}
}
// Load settings
void CMyAppUi::InternalizeSettingsDataL()
{
RFs& fs = iEikonEnv->FsSession();
RFileReadStream readStream;
TInt error = readStream.Open(fs, iSettingsFile, EFileRead);
TInt internalizationError = KErrNone;
// If file existed, try to read settings.
if (error == KErrNone)
{
TRAP(internalizationError, iData->LoadL(readStream);)
}
else
{
// Use default values in first time when no
// setting file exists
iData->SetDefaultValues();
}
readStream.Release();
// Reading failed, settings file might be corrupted.
if (internalizationError != KErrNone)
{
User::LeaveIfError(fs.Delete(iSettingsFile));
}
}
// Save settings
void CMyAppUi::ExternalizeSettingsDataL() const
{
RFs& fs = iEikonEnv->FsSession();
RFileWriteStream writeStream;
TInt error = writeStream.Open(fs, iSettingsFile, EFileWrite);
// Setting file did not exist, create one.
if (error != KErrNone)
{
User::LeaveIfError(writeStream.Create(fs, iSettingsFile, EFileWrite));
}
writeStream.PushL();
iData->SaveL(writeStream);
writeStream.CommitL();
writeStream.Pop();
writeStream.Release();
}
Streaming
Some examples of data streaming (reading):
// String
TBuf<100> iText;
aStream >> iText;
// Integer
TInt iVolume;
iVolume = aStream.ReadInt32L();
// Boolean
TBool iBinary;
iBinary = aStream.ReadInt16L();
// Ip address
TInetAddr iIpAddress;
iIpAddress.SetAddress(aStream.ReadUint32L());
// Time
TTime iTime;
TInt64 time;
aStream >> time;
iTime = TTime(time);
Postconditions
Application loads settings on startup and stores them on exit.
I was able to make this example work. Here are the bugs I found that need to be removed.
1. the closing bracket of the .h file is missing.
2. usually you have this line in your ConstructL function in CMyAppUi.cpp "BaseConstructL(EAknEnableSkin);"
it is also present in the code given here as example. Comment out any one of the two so that the program does not crash.
3. the poster forgot to add this line "_LIT(KSettingsFile, "settings.dat");"
this should be added in CMyAppUi.cpp where the other _LIT's have been defined. To be more precise, do not add this line inside a function. Add it inside the.cpp like you would include a .h file
Note: without this declaration, KSettingsFile will not exist and hence the program will give an error when the file is called.
Abdul