Question

我正在设计一个键盘类，只能检测键盘按键一次，但我仍然无法弄清楚这样做的方法。我的目标只是在同一个按键持续按下或保持按住时检查并执行一次操作，并且当同时按下2个操作键时不执行任何操作。例如，当我一直按住或按住键A时，动作1仅执行一次。然后我一直按下或按住另一个键B，动作2也执行一次。如果我同时按下A和B键，我就无法执行任何操作。

KeyboardClass标头和cpp文件中有两个类，即KeyboardClientClass和KeyboardServerClass。

////////////////////////////////////////////////////////////////////////////////
// Filename: KeyboardClass.h
////////////////////////////////////////////////////////////////////////////////
#ifndef _KEYBOARDCLASS_H_
#define _KEYBOARDCLASS_H_

////////////////////////////////////////////////////////////////////////////////
// Class prototype
////////////////////////////////////////////////////////////////////////////////
class KeyboardServerClass;


////////////////////////////////////////////////////////////////////////////////
// Class name: KeyboardClientClass
////////////////////////////////////////////////////////////////////////////////
class KeyboardClientClass
{
public:
    KeyboardClientClass( const KeyboardServerClass& KeyboardServer );
    ~KeyboardClientClass();
    bool KeyIsPressed( unsigned char keycode ) const;
    bool KeyIsPressedOnce( unsigned char keycode );

private:
    unsigned char tempKeyCode;
    const KeyboardServerClass& server;
};

class KeyboardServerClass
{
    friend KeyboardClientClass;

public:
    KeyboardServerClass();
    ~KeyboardServerClass();
    void OnKeyPressed( unsigned char keycode );
    void OnKeyReleased( unsigned char keycode );

   private:
        static const int nKeys = 256;
        bool keystates[ nKeys ];
        bool isKeyDown;
    };

    #endif


////////////////////////////////////////////////////////////////////////////////
// Filename: KeyboardClass.cpp
////////////////////////////////////////////////////////////////////////////////
#include "KeyboardClass.h"

KeyboardClientClass::KeyboardClientClass( const KeyboardServerClass& KeyboardServer ) 
: server ( KeyboardServer )
{
    tempKeyCode = 257;
}


KeyboardClientClass::~KeyboardClientClass()
{}


bool KeyboardClientClass::KeyIsPressed( unsigned char keycode ) const
{
    return server.keystates[ keycode ];
}



bool KeyboardClientClass::KeyIsPressedOnce( unsigned char keycode )
{
    if ( tempKeyCode != keycode )
    {
        tempKeyCode = keycode;
        return server.keystates[ keycode ];
    }
    else
    {
        return false;
    }
}


KeyboardServerClass::KeyboardServerClass()
{
    for ( int x = 0; x < nKeys; x++ )
    {
        keystates[ x ] = false;
    }
}


KeyboardServerClass::~KeyboardServerClass()
{
    isKeyDown = true;
}


void KeyboardServerClass::OnKeyPressed( unsigned char keycode )
{
    keystates [ keycode ] = true;
    isKeyDown = false;
}


void KeyboardServerClass::OnKeyReleased( unsigned char keycode )
{
    keystates [ keycode ] = false;
    isKeyDown = true;
}

首先，我创建一个KeyboardServer对象来跟踪Windows Procedure中的键盘乱码。

LRESULT CALLBACK SystemClass::MessageHandler( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam )
{
    switch ( msg )
    {
        //************ KEYBOARD MESSAGES ************ //

        // Check if a key has been pressed on the keyboard
        case WM_KEYDOWN:
        {
            if ( wParam == VK_ESCAPE )
                PostQuitMessage( 0 );

            // If a key is pressed send it to the KeyboardServer object so it can record the state
            m_KeyboardServer.OnKeyPressed( wParam );
            break;
        }

        // Check if a key has been released on the keyboard
        case WM_KEYUP:
        {
            // If a key is released then send it to the KeyboardServer object so it can unset the state for that key
            m_KeyboardServer.OnKeyReleased( wParam );
            break;
        }

        // ************ END KEYBOARD MESSAGES ************ //
}

然后，我在Game类中创建一个KeyboardClient对象来检查是否按下了某个键，并根据按下的键执行操作。

if ( m_Keyboard.KeyIsPressed( KEY_B ) )
    // Do action A
else if ( m_Keyboard.KeyIsPressed( KEY_N ) )
    // Do action B

Answer 1

WM_KEYDOWN消息的lParam值的位30表示在生成消息时密钥是否先前已关闭。您可以使用它来区分实际的按键和任何后续的键重复。

case WM_KEYDOWN:
    if (lParam & (1 << 30))
    {
        // this is a repeat
    }
    else
    {
        // first press
    }
    break;

但是，如果您正在尝试实时检查哪些密钥已关闭，则可以使用GetAsyncKeyState()功能执行此操作，而不是依靠通过消息循环跟踪keystate。

如何检测相同的键盘按键只按一次

1 个答案: