Question

我正在尝试使用SDL2制作一个简单的滚动射击游戏。我在屏幕上有一个移动的玩家，我试图让玩家使用阵列射击子弹（所以他们可以射击多个子弹）然而，当我按空格键时，没有任何反应，而是子弹图像的类型闪烁在左上角。

#include <SDL.h>
#include <stdio.h> //use for things like printf, same as cout
#include <iostream>
#include <string>
#include <time.h>
using namespace std;

//screend dimensions& sprtie dimensions
const int SCREEN_HEIGHT = 600;
const int SCREEN_WIDTH = 400;
const int SPRITE_WIDTH = 60;
const int SPRITE_HEIGHT = 80;

const int MAX_BULLETS = 50;

SDL_Window* Window = NULL;//the window rendering to
SDL_Surface* ScreenSurface = NULL;//surface contained by window
SDL_Surface* Background = NULL;
SDL_Surface* Player = NULL;
SDL_Surface* Enemy = NULL;
SDL_Surface* Bullet = NULL;
SDL_Surface* newBullet = NULL;

SDL_Rect posPlayer, posEnemy, posBullet, posnewBullet;

const Uint8* keystate = SDL_GetKeyboardState(NULL);
SDL_Event event;


class thePlayer
{
public:
thePlayer();

void player_movement();
void show_player();

private:


};

class theBullet
{
public:
theBullet();

bool isActive;
int x_position;
int y_position;

void bullet_movement();
void add_new_bullet();
void show_bullet();


private:

};
theBullet arrayofBullets[MAX_BULLETS];

class theEnemy
{
public:
theEnemy();

void enemy_movement();
void show_enemy();


private:
};


thePlayer::thePlayer()
{
posPlayer.x = 170;
posPlayer.y = SCREEN_HEIGHT;
posPlayer.w = 20;
posPlayer.h = 30;

}

void thePlayer::player_movement()
{
if(keystate[SDL_SCANCODE_LEFT])
    {
        posPlayer.x -= 2;
    }
if(keystate[SDL_SCANCODE_RIGHT])
    {
        posPlayer.x += 2;
    }
if(keystate[SDL_SCANCODE_UP])
    {
        posPlayer.y -= 2;
    }
if(keystate[SDL_SCANCODE_DOWN])
    {
        posPlayer.y += 2;
    }
if ((posPlayer.x + SPRITE_WIDTH) > SCREEN_WIDTH)
    {
        posPlayer.x = (SCREEN_WIDTH - SPRITE_WIDTH);
    }
if ((posPlayer.y + SPRITE_HEIGHT) > SCREEN_HEIGHT)
    {
        posPlayer.y = (SCREEN_HEIGHT - SPRITE_HEIGHT);
    }

}

void thePlayer::show_player()
{
SDL_BlitSurface(Player, NULL, ScreenSurface, &posPlayer);
SDL_SetColorKey(Player, SDL_TRUE, SDL_MapRGB(Player->format, 255, 255, 255));

}


theBullet::theBullet()
{
/*posBullet.x;
posBullet.y;
posBullet.w = 10;
posBullet.h = 15;*/
}

void theBullet::bullet_movement()
{
/*if(keystate[SDL_SCANCODE_SPACE])
{
    posBullet.x = posPlayer.x + 25;
    posBullet.y = posPlayer.y + 10;
}

posBullet.y -= 2;

if(posBullet.y < 0)
{
    posBullet.y = -50;

}*/
}

void theBullet::show_bullet()
{
//SDL_BlitSurface(Bullet, NULL, ScreenSurface, &posBullet);
//SDL_SetColorKey(Bullet, SDL_TRUE, SDL_MapRGB(Player->format, 255, 255,     255));//removes white background
}


theEnemy::theEnemy()
{
srand (time(NULL));

posEnemy.x = rand() % 300 + 50;
posEnemy.y =0;
posEnemy.w = 35;
posEnemy.h = 60;

}

void theEnemy::enemy_movement()
{
posEnemy.y += 1;

if(posEnemy.y > SCREEN_HEIGHT)
{
    posEnemy.y = SCREEN_HEIGHT +50;

}
}

void theEnemy::show_enemy()
{
SDL_BlitSurface(Enemy, NULL, ScreenSurface, &posEnemy);
SDL_SetColorKey(Enemy, SDL_TRUE, SDL_MapRGB(Player->format, 255, 255, 255));
}



bool initialise()
{
bool success = true;

if (SDL_Init(SDL_INIT_EVERYTHING) !=0)
{
    cout<<"SDL_Init Error."<<SDL_GetError()<<endl;
    success = false;
}
else
{
    //create the window for game
    Window = SDL_CreateWindow("Scrolling Shooter Game", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN);
    if (Window == NULL)
    {
        cout<<"Window Error"<<SDL_GetError()<<endl;
        success = false;
    }
    else
    {
        //get window surface
        ScreenSurface = SDL_GetWindowSurface(Window);
    }
}
return success;
}

bool LoadingMedia()
{
bool success = true;

Background = SDL_LoadBMP("background.bmp");
if (Background == NULL)
{
    cout<<"Error in loading background."<<SDL_GetError()<<endl;
    success = false;
}

Player = SDL_LoadBMP("spaceship.bmp");
if (Player == NULL)
{
    cout<<"Error in loading player."<<SDL_GetError()<<endl;
    success = false;
}

Enemy = SDL_LoadBMP("enemy.bmp");
if (Enemy == NULL)
{
    cout<<"Error in loading enemy."<<SDL_GetError()<<endl;
    success = false;
}

Bullet = SDL_LoadBMP("bullet.bmp");
if (Bullet == NULL)
{
    cout<<"Error in loading bullet."<<SDL_GetError()<<endl;
    success = false;
}

return success;
}

void closedown()
{
SDL_FreeSurface(Background);
Background = NULL;
SDL_FreeSurface(Player);
Player = NULL;
SDL_FreeSurface(Enemy);
Enemy = NULL;

SDL_DestroyWindow(Window);
Window = NULL;

SDL_Quit();
}

int main(int argc, char** argv)
{
bool quit = false;
thePlayer myPlayer;
theEnemy myEnemy;
theBullet myBullet;

if (!initialise())
{
    cout<<"Failed to initialise"<<SDL_GetError()<<endl;
}
else
{
    if (!LoadingMedia())
    {
        cout<<"Error loading media"<<SDL_GetError()<<endl;
    }
}

//makes all bullets false
for (int i=0; i<MAX_BULLETS; i++)
{
    arrayofBullets[i].isActive = false;
}

//GAME LOOP
while (quit == false)
{
    SDL_BlitSurface(Background, NULL, ScreenSurface, NULL);
    myPlayer.show_player();
    myPlayer.player_movement();

    while (SDL_PollEvent(&event))
    {
        if( event.type == SDL_QUIT )
        {
            quit = true;
            break;
        }

    if(keystate[SDL_SCANCODE_SPACE])
    {
        for (int i=0; i<MAX_BULLETS; i++)
        {
            if (arrayofBullets[i].isActive == false)
            {
                arrayofBullets[i].x_position = posPlayer.x + 25;
                arrayofBullets[i].y_position = posPlayer.y + 10;
                arrayofBullets[i].isActive = true;
                break;
            }
        }
    }
    //update game objects
    for (int i=0; i<MAX_BULLETS; i++)
    {
        if (arrayofBullets[i].isActive == true)
        {
            arrayofBullets[i].y_position -= 2;

            if (arrayofBullets[i].y_position < 0)
            {
                arrayofBullets[i].isActive = false;
            }
        }
    }

    for (int i=0; i<MAX_BULLETS; i++)
    {
        if (arrayofBullets[i].isActive == true)
        {
            SDL_BlitSurface(Bullet, NULL, ScreenSurface, NULL);
        }
    }

    }
    //myPlayer.show_player();
    //myBullet.show_bullet();
    //myEnemy.show_enemy();
    //myPlayer.player_movement();
    //myBullet.bullet_movement();
    //myEnemy.enemy_movement();

    SDL_UpdateWindowSurface(Window); //updates screen
}

closedown();

return 0;

}

Answer 1

SDL_BlitSurface(Bullet, NULL, ScreenSurface, NULL);

您还没有指定目标矩形，因此它会在左上角显示。

应该是

SDL_Rect dstrect;
dstrect.x = arrayofBullets[i].x_position;
dstrect.y = arrayofBullets[i].y_position;
dstrect.w = Bullet->w;
dstrect.h = Bullet->h;
SDL_BlitSurface(Bullet, NULL, ScreenSurface, &dstrect);

SDL2＆＃39;子弹＆＃39;运动不起作用？

1 个答案: