c++ - 继承和指针数组

Question

如果我有一个继承自 2 个不同类的类，并且我想将新类放入一个数组中。该数组仅包含指向其中一个继承类的指针。该数组会溢出还是指针数组只会“包含”从创建数组的类继承的类的一部分？

例子:

我有一个名为“screens”的类，它有 3 个指针数组来保存对其他对象的引用。

        class Screens
{
        protected:

        //Edit these to fit the amount of elements used to save space :-) Then we don't need to use dynamic (8 bit MCU :-()
        #define NUMBER_OF_BUTTONS 10
        #define NUMBER_OF_GRAPHS 10
        #define NUMBER_OF_TXTS 10

        UTFT *scr;
        UTouch *touch;

        ButtonTft *buttons[NUMBER_OF_BUTTONS];
        GraphTft *graphs[NUMBER_OF_GRAPHS];
        TFT_printer *texts[NUMBER_OF_TXTS];

        uint8_t ellementsButtons;
        uint8_t ellementsGraphs;
        uint8_t ellementsTexts;

        uint8_t addButIndex;
        uint8_t addGrafIndex;
        uint8_t addTxtIndex;


        public:
        Screens(UTFT *_screen);
        void addButton(ButtonTft *but);
        void addGraphs(GraphTft *graf);
        void addText(TFT_printer *txt);
        void printScreen(uint8_t textToPrint = ALL_TXT, graphIDs_e graphToDraw = ALL_GRAPS);
        void printButton(uint8_t index,bool presed = false);
        void printButton(buttonIDs_e buttonID,bool presed = false);
        void printGraph(graphIDs_e graphMode = ALL_GRAPS,bool whatToClear = WHOLE_GRAPH);
        void printTxt(uint8_t txtMode = ALL_TXT);
        ButtonTft* getButton(buttonIDs_e buttonID);
        uint8_t getButtonIndex(buttonIDs_e buttonID);
        ButtonTft* getPressedButton(uint8_t x,uint8_t y);
        GraphTft* getGraph(graphIDs_e graphID);
        GraphTft* getPressedGraph(uint8_t x, uint8_t y);
    `};

然后我有另一个名为“按钮”的类，它是屏幕上的一个按钮。

#define PRESSED true

    class ButtonTft
    {
        public:
        ButtonTft(UTFT *TFTdisplay, int xTopL,int yTopL, int xButR, int yButR,buttonIDs_e buttonID);
        ~ButtonTft();
        void drawButton(bool pressed = false);
        void setPos(int x, int y);//This is never used... remove?
        void text(char *txt);
        bool isPressed(uint16_t x, uint16_t y);
        buttonIDs_e getButtonID();

        protected:

        buttonIDs_e _buttonID;
        uint16_t xTopLeft;
        uint16_t yTopLeft;
        uint16_t xButRight;
        uint16_t yBotRight;
        char    *butonText;
        uint16_t color;
        UTFT    *scr;
    };

按钮像这样添加到屏幕上:

/*==============================================================================
| Function Name: addButton
|   Description: Adds a button element to the screen.
|         Input: A pointer to the button element
|        Return: -
*=============================================================================*/
void Screens::addButton(ButtonTft *but)
{
    buttons[addButIndex++] = but;//Add the element to the array
    if (addButIndex == NUMBER_OF_BUTTONS+1) addButIndex = 0;//Should not do this. Avoid adding more than 10! But Safety first!
    if(ellementsButtons++ == NUMBER_OF_BUTTONS+1) ellementsButtons = NUMBER_OF_BUTTONS;//Safety first!
}

然后通过对按钮对象的引用调用该函数:

module5.addButton(&backButton);

现在我想创建一个名为“模块”的新类，它继承自“屏幕”和“按钮”。我的想法是，该模块是一个带有屏幕的按钮。

class Modules : public Screens , public ButtonTft
{
 public:
    Modules(UTFT *_display, int xTopL,int yTopL, int xButR, int yButR, buttonIDs_e buttonID);
    bool isConected;
 protected:
};

我像这样将构造函数参数传递给继承的类:

 Modules::Modules(UTFT *_display, int xTopL,int yTopL, int xButR, int yButR, buttonIDs_e buttonID) : Screens (_display) , ButtonTft (_display, xTopL, yTopL, xButR, yButR, buttonID)
{
    isConected = 0;
}

我想将所有模块收集到一个屏幕对象中，这意味着，我想将这些模块放入“屏幕”对象中的按钮指针数组中。 (因为模块继承自按钮。)我还想将其他按钮添加到“模块”对象，因为它也继承自屏幕类。

Modules module5(&display,10,75,100,100,MODULE_5);
module5.addButton(&backButton);
mainScreen.addButton(&module5);

如果我将新对象(如新按钮)添加到我的模块对象，然后将该对象添加到屏幕，屏幕类中的按钮引用数组是否会溢出？

感谢您的帮助。

Answer 1

我看不出 Modules 应该从 ButtonTft 继承的理由。这会给模块添加不必要的数据。如果您需要从模块访问 ButtonTft 的 protected 成员(这将是糟糕的编程)，请将其添加为好友。该数组不会溢出，除非您将太多元素放入其中。