Question

我有一个7 x 7的探针矩阵，可以传递一个信号，表示在调查区域内测量的水平。我可以在SDL中绘制一个7 x 7矩形的矩形，但我无法更新颜色我上课了类探针 { 上市：探测（）; 〜探针（）; void SetColor（int x）; void Set_id（int x，int y，int z）;
void Level_id（void）;

private: 
    int OldColor; 
    int Xcord; 
    int Ycord; 
    SDL_Rect rect; //This does not keep the rect that I create?
};
//outside all curly brackets {} I have 
Probe Level[7][7];
//I initialize each instance of my class 
Level[x][y].Set_id(x, y, z); and I use x and y to create and position the rectangle
//  Defininlg rectangles
    SDL_Rect rect = {BLOCK_W * Xcord, BLOCK_H * Ycord, BLOCK_W, BLOCK_H};
/*I get what I expected, by the way z sets the color and it is incremented so each rectangle has a      different color. */

//I used function SetColor, it failed untill I regenerated rect
//in the SetColor function.  I have
private:
SDL_Rect rect;
//It is private why do I need to re-create the SDL_Rect rect?
//Why is it not stored like 
private:
int Xcord; // !!?  Regards Ian.

Answer 1

如果我理解正确，你的班级看起来像这样：

class Probe {
public:
   Probe();
   ~Probe();

   void SetColor(int x);
   void Set_id(int x, int y, int z) {
      SDL_Rect rect = {BLOCK_W * Xcord, BLOCK_H * Ycord, BLOCK_W, BLOCK_H};
   }
private:
   int OldColor; 
   int Xcord; 
   int Ycord; 
   SDL_Rect rect;
};

你想知道为什么＆＃34; rect＆＃34;变量不会保存为私有变量，以及在绘制SDL_Rect时如何更改颜色？

首先，你的＆＃34; rect＆＃34;没有得到保存，因为你正在定义一个新的＆＃34; rect＆＃34;函数中的变量。你应该做的是：

rect = {BLOCK_W * Xcord, BLOCK_H * Ycord, BLOCK_W, BLOCK_H};

或

rect.x = BLOCK_W * Xcord;
rect.y = BLOCK_H * Ycord;
rect.w = BLOCK_W;
rect.h = BLOCK_H;

要更改渲染的颜色（假设您正在使用SDL_RenderDrawRect函数，因为这是我所知道的唯一可以绘制SDL_Rects的函数），您只需调用：

SDL_SetRenderDrawColor(int r, int g, int b, int a);

在调用SDL_RenderDrawRect函数之前（每次）。如果你不这样做，并在其他地方调用SetRenderDrawColor函数，你的颜色将变为该颜色。

cpp私有数据成员SDL_Rect不活动

1 个答案: