qt将对象传递给不同的类

Question

修改

我在 dialog.cpp 中启动程序时最初创建所有对象，并将所有QPixmaps存储在一个数组中，然后从中挑选一个随机的。那个随机的QPixmap我想传递给我的maintargets类并在场景中绘制（也是在dialog.cpp中创建的）。

// dialog.cpp

#include "dialog.h"
#include "scene.h"
#include "ui_dialog.h"
#include "instructions.h"
#include "settings.h"
#include "highscore.h"
#include "maintargets.h"
#include <stdlib.h>

Dialog::Dialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::Dialog)
{
    ui->setupUi(this);

    // Create and configure scene
     scene = new Scene;
     scene->setBackgroundBrush(Qt::black);
     scene->setItemIndexMethod(QGraphicsScene::NoIndex);
     ui->graphicsView->setScene(scene);
     scene->setSceneRect(-200, -150, 400, 300);
     ui->graphicsView->setMouseTracking(true);

     QPixmap tankbase1(":/images/tankbase.jpg");
     ui->tankbaseplay1->setPixmap(tankbase1);

     //Store targets in array and random generator
     index = 0;
     main_targets[0] = QPixmap(":images/darkbluelogo.jpg)");
     main_targets[1] = QPixmap(":images/graylogo.jpg");
     main_targets[2] = QPixmap(":images/lightbluelogo.jpg");
     main_targets[3] = QPixmap(":images/limE.jpg");
     main_targets[4] = QPixmap(":images/pink.jpg");
     main_targets[5] = QPixmap(":images/purple.jpg");
     main_targets[6] = QPixmap(":images/redlogo.jpg");
     main_targets[7] = QPixmap(":images/yellow.jpg");
     main_targets[8] = QPixmap(":images/brown.jpg");

     index = qrand((index % 9) + 1);

     //scene->addItem(main_targets[index]);


     //Timer for scene advancement
     QTimer *timer = new QTimer();
     QObject::connect(timer, SIGNAL(timeout()), scene, SLOT(advance()));
     timer->start(100);

}

Dialog::~Dialog()
{
    delete ui;
}

// maintargets.h

#ifndef MAINTARGETS_H
#define MAINTARGETS_H
#include "dialog.h"
#include <QGraphicsItem>
#include <QGraphicsScene>
#include <QPainter>
#include <QRect>

class MainTargets : public QGraphicsScene
{
public:
    MainTargets();
    QRectF boundingRect() const;
    QPainterPath shape() const;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);

protected:
    void advance(int step);

private:  
    qreal dx, dy;
    qreal x, y;
    qreal w, h;

};


#endif // MAINTARGETS_H

// maintargets.cpp

#include "maintargets.h"

MainTargets::MainTargets()
{
    dx = -0.005;
    dy = 0.0;
    x = 1.5;
    y = 0.0;
    w = 100.0;
    h = 70.0;

}

QRectF MainTargets::boundingRect() const
{
    qreal shift = 1;
        return QRectF(-w/2 -shift, - h/2
                      - shift, w + shift, h + shift);
}

QPainterPath MainTargets::shape() const
{
    QPainterPath path;
    path.addRect(boundingRect());
    return path;
}

void MainTargets::paint(QPainter *painter,
                        const QStyleOptionGraphicsItem *option,
                        QWidget *widget)
{        
    painter->drawPixmap(-w/2, -h/2, main_targets[index]);
}

void MainTargets::advance(int step)
{
    if(step == 0) return;
    x = x + dx;
    y = y + dy;
    setPos(mapToParent(x, y));
}

绘制后，它向x方向移动。

Answer 1

遗憾的是，您的问题非常广泛，具体解决方案取决于您的使用案例。我将为您的问题提一些不同的解决方案，然后您可以看看，但请阅读有关如何在Stack Overflow上提问的文档，因为您的问题目前质量非常低。

1）如果你的操作应该构建另一个类，你可以将它作为构造函数参数传递，如果它不是你的设计构造这个类。

2）如果可以通过这种方式扩展您的类，您可以使用void setPixmap(QPixmap); setter，并且您可以访问该方法中的对象实例。

3）你可以使用代理类处理所有这些，如果这是你在操作中获得随机索引的所有权限。

4）如果另一个类需要在同一个源文件中，则可以在同一个源文件中设置静态变量。这一般不是一个好主意，但我也看到了这种情况。

5）您可以设置其他类方法正在使用的全局变量。再次，这是一个非常糟糕的做法。

6）您可以直接将此QPixmap作为参数传递给另一个类中的绘图函数。

7）您可以将此传递给代理类对象，该代理类对象将其传递给另一个类的绘图方法。

8）如果另一个班级处于不同的过程中，你至少可以通过另外两种方式来传递它。

正如我所说，这实际上取决于您的情况，并且有很多方法可以做到这一点。话虽这么说，我稍后会删除这个答案，因为这个问题太宽泛了，但我希望告诉你你的要求有多宽。

Answer 2

简单的参考传递是我迷失的。这解释了在maintargets类中获取QPixmap变量所需的过程。

// dialog.h

private:
    Ui::Dialog *ui;
    //add a pointer
    MainTargets* pmap;

// dialog.cpp

#include "dialog.h"
#include "ui_dialog.h"
#include "maintargets.h"
#include <stdlib.h>

Dialog::Dialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::Dialog)
{
    ui->setupUi(this);

    // Create and configure scene
     scene = new Scene;
     scene->setBackgroundBrush(Qt::black);
     scene->setItemIndexMethod(QGraphicsScene::NoIndex);
     ui->graphicsView->setScene(scene);
     scene->setSceneRect(-200, -150, 400, 300);
     ui->graphicsView->setMouseTracking(true);

     QPixmap tankbase1(":/images/tankbase.jpg");
     ui->tankbaseplay1->setPixmap(tankbase1);

     //Store targets in array and random generator
     index = 1;
     main_targets[0] = QPixmap(":images/darkbluelogo.jpg)");
     main_targets[1] = QPixmap(":images/graylogo.jpg");
     main_targets[2] = QPixmap(":images/lightbluelogo.jpg");
     main_targets[3] = QPixmap(":images/lime.jpg");
     main_targets[4] = QPixmap(":images/pink.jpg");
     main_targets[5] = QPixmap(":images/purple.jpg");
     main_targets[6] = QPixmap(":images/redlogo.jpg");
     main_targets[7] = QPixmap(":images/yellow.jpg");
     main_targets[8] = QPixmap(":images/brown.jpg");



     //Timer for scene advancement
     QTimer *timer = new QTimer();
     QObject::connect(timer, SIGNAL(timeout()), scene, SLOT(advance()));
     timer->start(10);

}

Dialog::~Dialog()
{
    delete ui;
}


void Dialog::on_startButton_clicked()
{
    ui->settingsButton->hide();
    ui->titlescreen->hide();
    ui->highscoreButton->hide();
    ui->instructionButton->hide();
    ui->startButton->hide();

    QGraphicsTextItem *FirstP;
    QString P1 = "Player1";
    FirstP = scene->addText(P1);
    FirstP->setFont(QFont("Nimbus Mono L", 12,QFont::Bold));
    FirstP->setDefaultTextColor(Qt::white);
    FirstP->setPos(-300, -220);


    QGraphicsTextItem *SecondP;
    QString P2 = "Player2";
    SecondP = scene->addText(P2);
    SecondP->setFont(QFont("Nimbus Mono L", 12,QFont::Bold));
    SecondP->setDefaultTextColor(Qt::white);
    SecondP->setPos(230, -220);

    //Initializes function
    setPixmaps();
}

void Dialog::setPixmaps()
{
    index = (qrand() % (9));
    //Add a new MainTarget and set equal to new pointer created in header file
    pmap = new MainTargets(main_targets[index]);
    pmap->setPos(355,0);
    scene->addItem(pmap);

}

// maintargets.h

private:   
    //Add a new QPixmap to header
    QPixmap p;

// maintargets.cpp

在构造函数中的QPixmap变量中引用并设置为等于新创建的指针

#include "maintargets.h"

MainTargets::MainTargets(QPixmap& nomTargets)
{

    dx = -0.005;
    dy = 0.0;
    x = 0.0;
    y = 0.0;
    w = 100.0;
    h = 70.0;

    p = nomTargets;

}

QRectF MainTargets::boundingRect() const
{
    qreal shift = 1;
        return QRectF(-w/2 -shift, - h/2
                      - shift, w + shift, h + shift);
}

QPainterPath MainTargets::shape() const
{
    QPainterPath path;
    path.addRect(boundingRect());
    return path;
}

void MainTargets::paint(QPainter *painter,
                        const QStyleOptionGraphicsItem *option,
                        QWidget *widget)
{
    //Set that pointer variable as the source for the 
    //given drawPixmap memeber

    painter->drawPixmap(-w/2, -h/2, p);