Simple keyboard wrapper for games
Article Metadata
This article presents a simple class to handle keyboard input in a game-like way.
Class declaration
// INCLUDES
#include <e32keys.h>
#include <e32std.h>
// CLASSES
/**
* A simple keyboard wrapper.
*/
class TKeyboardWrapper
{
public:
// key codes not found in header files
enum TKeys {
EKey0 = 48,
EKey1,
EKey2,
EKey3,
EKey4,
EKey5,
EKey6,
EKey7,
EKey8,
EKey9,
EKeyShift = 127,
EKeyStar = 133
};
public:
/**
* Default constructor.
*/
TKeyboardWrapper ()
{ Clear (); }
/**
* Clears key state.
*/
void Clear ()
{ Mem::FillZ (iKeys, 256); }
/**
* Asks if some key is down.
*/
TBool IsKeyDown (TInt aKey) const
{ ASSERT (aKey >= 0 && aKey < 256); return iKeys [aKey]; }
/**
* Sets a key as down.
*/
void SetKey (TInt aKey)
{ ASSERT (aKey >= 0 && aKey < 256); iKeys [aKey] = ETrue; }
/**
* Sets a key as up.
*/
void ClearKey (TInt aKey)
{ ASSERT (aKey >= 0 && aKey < 256); iKeys [aKey] = EFalse; }
/**
* Check if any key is down.
*/
TBool AnyKeyDown () const
{
for (TInt16 i = 0; i < 256; ++i)
{
if (iKeys [i])
return true;
}
return false;
}
private:
TBool iKeys [256];
};
Usage
It is necessary to collect the keyboard data in some of the methods that receive keyboard input. For example, using the HandleKeyEventL() of the Application UI class:
TKeyResponse CMyAppUi::HandleKeyEventL (const TKeyEvent& aKeyEvent, TEventCode aType)
{
if (aType == EEventKeyDown)
iKeyboard.SetKey (aKeyEvent.iScanCode);
else
if (aType == EEventKeyUp)
iKeyboard.ClearKey (aKeyEvent.iScanCode);
return EKeyWasConsumed;
}
In the example, iKeyboard is a TKeyboardWrapper instance. Later, to get the key state it is necessary to use the constants defined in the TStdScanCode enum (e32keys.h). Example:
void CMyAppUi::ProcessInput ()
{
if (iKeyboard [EStdKeyLeftArrow] )
// left arrow is down
if (iKeyboard [TKeyboardWrapper::EKey0] )
// 0 key is down
}
It is important not to use the constants defined in the TKeyCode enum, because their use leads to incorrect behavior and possibly to an invalid array access.
