異常在0x71002A85（SDL2_ttf.dll）拋出

Question

所以我創建一個使用SDL2和C++（我完全新本！）一切都進行得很順利，直到我打這個錯誤2D乒乓球比賽：

Exception thrown at 0x71002A85 (SDL2_ttf.dll) in 2D Game.exe: 0xC0000005: Access violation reading location 0x00000000. 

代碼中斷：

SDL_Surface * surf = TTF_RenderText_Blended（font，message.c_str（），color）;

#include "utilities.h" 

#include <SDL.h> 
#include <SDL_ttf.h> 

void renderTexture(SDL_Texture* tex, 
     SDL_Renderer* ren, SDL_Rect dst, SDL_Rect *clip) { 
    SDL_RenderCopy(ren, tex, clip, &dst); 
} 

void renderTexture(SDL_Texture* tex, 
     SDL_Renderer* ren, int x, int y, SDL_Rect* clip) { 
    SDL_Rect dst; 
    dst.x = x; 
    dst.y = y; 
    if (clip != nullptr) { 
     dst.w = clip->w; 
     dst.h = clip->h; 
    } else { 
     SDL_QueryTexture(tex, nullptr, nullptr, &dst.w, &dst.h); 
    } 

    renderTexture(tex, ren, dst, clip); 
} 

SDL_Texture* renderText(const std::string &message, 
    const std::string &fontFile, SDL_Color color, 
    int fontSize, SDL_Renderer* renderer) { 

    TTF_Font* font = TTF_OpenFont(fontFile.c_str(), fontSize); 

SDL_Surface* surf = TTF_RenderText_Blended(font, message.c_str(), color); 

SDL_Texture* texture = SDL_CreateTextureFromSurface(renderer, surf); 

SDL_FreeSurface(surf); 
TTF_CloseFont(font); 

return texture; 

} 

Answer 1

您應該檢查font之前在行上返回的對象爲null。如果TTF_OpenFont無法打開給定的字體文件，它很有可能返回null。

TTF_Font* font = TTF_OpenFont(fontFile.c_str(), fontSize); 

if(!font) { 
    ... //some action here, perhaps throw exception 
} 
SDL_Surface* surf = TTF_RenderText_Blended(font, message.c_str(), color);