SDL x和y运动

Question

为什么这段代码不能让我向上或向左移动？

while( quit == false )
    { 


    apply_surface( 0,0, back,screen );
    apply_surface( playerx,playery,player, screen );


    SDL_Flip( screen );

        //While there's an event to handle
        while( SDL_PollEvent( &event ) )
        {
            if(event.type == SDL_KEYDOWN)
            {
                switch(event.key.keysym.sym)
                {
                case SDLK_UP:playery=playery-10;
                case SDLK_DOWN:playery=playery+10;
                case SDLK_LEFT:playerx=playerx-10;
                case SDLK_RIGHT:playerx=playerx+10;
                }
            }       

Answer 1

您需要在每种case在switch之后使用一个break ，否则执行会“下降”到下一行，从而有可能取消您的操作（实际上SDLK_UP和SDLK_LEFT是取消操作）