有人可以帮我修改此代码。 我正在尝试显示棋盘格C ++ QT

Question

I'm new to Qt and C++. I'm trying to create a checker/chess board where each square is an object. What I'm trying to figure out is how to have each square object be a part of the board object I'm declaring and display that on the screen. I can display a widget on the screen by using MyWidget.show() in the main class. But I want to do something like Board.show() and have all of the square objects that are members of that class(that have a height, width, and color) show up. With the code I tried nothing showed up, although I was able to get a square to show up that was NOT in the board class.

main.cpp

#include <qtgui>
#include "square.h"
#include "board.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    //Square square;
    //square.show();
    Board board;
    board.show();
    return app.exec();
}

board.h and board.cpp

#ifndef BOARD_H
#define BOARD_H

#include <QWidget>

class Board : public QWidget
{
public:
    Board();
};

#endif // BOARD_H

#include "board.h"
#include "square.h"

Board::Board()
{
    Square square;
    //square.show();
}

square.h and square.cpp* strong text *

#ifndef SQUARE_H
#define SQUARE_H

#include <QWidget>

class Square : public QWidget
{
public:
    Square();

protected:
    void paintEvent(QPaintEvent *);
};

#endif // SQUARE_H

#include "square.h"
#include <QtGui>

Square::Square()
{
    QPalette palette(Square::palette());
    palette.setColor(backgroundRole(), Qt::white);
    setPalette(palette);
}

void Square::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing);
    painter.setBrush(QBrush("#c56c00"));
    painter.drawRect(10, 15, 90, 60);
}

Answer 1

Your Square is created as an automatic variable (ie, its lifetime is the scope of the constructor of Board ). show() will make a widget visible, as long as the event loop can handle the widget, which is not the case here ( square will be deleted before the event loop).

Also, you should add the Q_OBJECT macro in every class derived from QObject . Board is derived from QWidget , which is derived from QObject .

So, change your class Board :

class Square;
class Board : public QWidget
{
Q_OBJECT
public:
    Board();
private:
    Square* square;
};

the constructor:

Board::Board()
{
    square = new Square();
    square->show();
}

and the destructor:

Board::~ Board()
{
    delete square;
}

Note: for me, having a Square class is useless. You can paint a grid in the paintEvent of Board , it will be faster, consume less memory, and be easier to maintain.

EDIT : here is a better method:

void Board::paintEvent(QPaintEvent* pe)
{
    // Initialization
    unsigned int numCellX = 8, numCellY = 8;
    QRect wRect = rect();
    unsigned int cellSizeX = wRect.width() / numCellX;
    unsigned int cellSizeY = wRect.height() / numCellY;
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing);

    // Draw the background. The whole widget is drawed.
    painter.setBrush(QColor(0,0,0)); //black
    painter.drawRect(wRect);

    // Draw the cells which are of the other color
    // Note: the grid may not fit in the whole rect, because the size of the widget
    // should be a multiple of the size of the cells. If not, a black line at the right
    // and at the bottom may appear.
    painter.setBrush(QColor(255,255,255)); //white
    for(unsigned int j = 0; j < numCellY; j++)
        for(unsigned int i = j % 2; i < numCellX; i+=2)
            painter.drawRect(i * cellSizeX, j * cellSizeY, cellSizeX, cellSizeY);
}