Ch02: Game Class and Loop

《SDL Game Development》中有这样一个游戏的流程图

这个game loop 在游戏开发里面用到的每每是下面一种

《Game Programming Patterns》 http://gameprogrammingpatterns.com/game-loop.html

下面是一个game loop实现的示例代码

void init(){}
void render(){}
void update(){}
void handleEvents(){}
void clean(){}
bool g_bRunning = true;
int main()
{
init();
while(g_bRunning)
{
handleEvents();
update();
render();
}
clean();
}

一般游戏循环会按照帧率刷新，因此实现代码以下：

double lastTime = getCurrentTime();
while (true)
{
  double current = getCurrentTime();
  double elapsed = current - lastTime;
  processInput();
  update(elapsed);
  render();
  lastTime = current;
}```

如下实现一个简单的game class

**GameApp.h**

#pragma once #include <SDL.h> class GameApp { public: GameApp(); ~GameApp();

bool Init( );
void OnEvent(SDL_Event* event);
void GameLoop();
void Render();
void Cleanup();
int OnExecute();

private: bool m_bRunning; SDL_Window* m_pWindow; SDL_Renderer* m_pRenderer; };

**GameApp.cpp**

#include "GameApp.h" #include <iostream> GameApp::GameApp() { if (!Init()) throw std::runtime_error("Init SDL error"); }

GameApp::~GameApp() { } bool GameApp::Init( ) { m_bRunning = true; if (SDL_Init(SDL_INIT_EVERYTHING) < 0) { std::cerr << "can not init SDL" << std::endl; return false; } if (SDL_CreateWindowAndRenderer(640, 480, SDL_WINDOW_SHOWN, &m_pWindow, &m_pRenderer) < 0) { std::cerr << "can not create render" << std::endl; return false; } SDL_SetWindowTitle(m_pWindow, "Game App");

return true;

} void GameApp::OnEvent(SDL_Event* event) { if (event->type == SDL_QUIT) { m_bRunning = false; } } void GameApp::GameLoop() {

} void GameApp::Render() { SDL_RenderClear(m_pRenderer); SDL_RenderPresent(m_pRenderer);

} void GameApp::Cleanup() { SDL_DestroyRenderer(m_pRenderer); SDL_DestroyWindow(m_pWindow); } int GameApp::OnExecute() {

SDL_Event event;
while (m_bRunning)
{
	while (SDL_PollEvent(&event))
	{
		OnEvent(&event);
	}
	Render();
}
Cleanup();
return 0;

}

**main.cpp**

#include "GameApp.h"

int main(int argc, char** argv) { GameApp app; return app.OnExecute(); }

代码放在如下路径了
SDL game class.zip
> http://pan.baidu.com/s/1nvwjmm1