C ++和SDL问题

Question

I want to blit surfaces that I've created in two classes. One is called Map , that holds the relevant map vector as well as some other stuff. The other is a Tile class. There is a problem when I run the program.

I get no errors, and the program runs as it should. Any ideas? It's probably a stupid mistake somewhere.

Map populate

    void map::Populate(map M)
    for(int x=0;x<=19;x++)
    {
        for(int y=0;y<=15;y++)
        {
            int y2 = (y*32);
            int x2 = (y*32);
            Tile T(x2,y2);
            M.AddToMap(&T);
            printf("Added Tile");

Render

    void map::Render(SDL_Surface* screen)
    {
    for(int x=0;x<grid.size();x++)
    {
            printf("test");
            Tile* T = grid[x];
            SDL_Surface* k = T->GetIcon();
            SDL_Rect dstrect;
            dstrect.x = (screen->w - k->w) / 2;
            dstrect.y = (screen->h - k->h) / 2;
            SDL_BlitSurface(k, 0, screen, &dstrect);

Answer 1

You're not stating what the problem actually is, just that the program "runs as it should".

Problems in your code:

int x2 = (y*32); should likely be x*32.

void map::Populate(map M) takes a map by value - this copies the map you pass, and any changes will not be visible in the passed map. map & M passes a reference, so changes will be seen in the map you pass.

M.AddToMap(&T) adds a pointer to the local Tile variable, which gets invalidated each iteration of the inner loop. More likely you want new Tile(T) there, or better yet a smart pointer such as boost's shared_ptr . Remember that you also need to delete those Tiles if you don't use a smart pointer.

New code:

void map::Populate(map & M)
for(int x=0; x<20; x++)
{
    for(int y=0; y<16; y++)
    {
        int y2 = (y*32);
        int x2 = (x*32);
        M.AddToMap(new Tile(x2,y2));
        printf("Added Tile");

Answer 2

You are adding a reference to a local variable to your map in Populate. If the method doesn't make a copy of the input, this is most likely wrong. Make a copy (pass by value) or store a smart pointer to your Tile. Of course you can store a plain old pointer, but make sure to delete those Tiles in the end!

Answer 3

假设您的问题是图像没有显示，您可能需要发布屏幕和表面的设置代码，以便我们查看是否是问题所在。