如何在Qt中访问其他类的对象？

Question

在程序中，我想单击主窗口中的一个按钮并触发子窗口以显示图像。但是我无法在主窗口中访问uii> graphSview.cpp，我该怎么做？在main.cpp中。假定点击按钮功能可以执行此类操作。QgraphicsView放置在showpic类中。

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QFileSystemModel>
#include "showpic.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
private slots:
    void on_pushButton_clicked();
private:
    Ui::MainWindow *ui;
    QFileSystemModel *model;
    ShowPic *showpic;
    QString filesPath;
};
#endif // MAINWINDOW_H

showpic.h

#ifndef SHOWPIC_H
#define SHOWPIC_H
#include <QWidget>
namespace Ui {
class ShowPic;
}
class ShowPic : public QWidget
{
    Q_OBJECT
public:
    explicit ShowPic(QWidget *parent = 0);
    ~ShowPic();
private:
    Ui::ShowPic *ui;
};
#endif // SHOWPIC_H

main.cpp

#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include<QFileDialog>
#include<QFileSystemModel>
#include<QStringList>
#include <QTreeView>
#include <QGraphicsScene>
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}
MainWindow::~MainWindow()
{
    delete ui;
}
void MainWindow::on_pushButton_clicked()
{
    showpic = new ShowPic();
    showpic->show();
    QGraphicsScene scene;
    QPixmap pixmap("C:test\image.jpg");
    scene.addPixmap(pixmap);
    ui->graphicsView->setScene(&scene); ///????
}

showpic.cpp

#include "showpic.h"
#include "ui_showpic.h"
ShowPic::ShowPic(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::ShowPic)
{
    ui->setupUi(this);
}
ShowPic::~ShowPic()
{
    delete ui;
}

Answer 1

首先，您必须仅添加QGraphicsScene一次，并且在构造函数中有一个合适的位置：

ShowPic::ShowPic(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::ShowPic)
{
    ui->setupUi(this);
    ui->graphicsView->setScene(new QGraphicsScene);
}

然后，我们创建一种接收PixMap并将其添加到场景的方法：

showpic.h

[...]
explicit ShowPic(QWidget *parent = 0);
~ShowPic();
void addPixmap(const QPixmap &pixmap);
[...]

showpic.h

[...]
void ShowPic::addPixmap(const QPixmap &pixmap){
    ui->graphicsView->scene()->addPixmap(pixmap);
}
[...]

我们在插槽中使用该方法on_pushbutton_clicked：

void MainWindow::on_pushButton_clicked()
{
    showpic = new ShowPic();
    QPixmap pixmap("C:test\image.jpg");
    showpic->addPixmap(pixmap);
    showpic->show();
}