用Qt写一个预览多张图片的程序，及窗口放大缩小的程序

以下是一个使用Qt编写的预览多张图片的程序和窗口放大缩小的程序示例：

预览多张图片的程序：

#include <QApplication>
#include <QMainWindow>
#include <QScrollArea>
#include <QGridLayout>
#include <QLabel>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QMainWindow *window = new QMainWindow;
    QWidget *centralWidget = new QWidget(window);
    QGridLayout *gridLayout = new QGridLayout(centralWidget);

    QScrollArea *scrollArea = new QScrollArea(centralWidget);
    scrollArea->setWidgetResizable(true);
    QWidget *scrollWidget = new QWidget(scrollArea);
    QGridLayout *scrollLayout = new QGridLayout(scrollWidget);
    scrollArea->setWidget(scrollWidget);

    for (int i = 1; i <= 10; ++i) {
        QLabel *label = new QLabel(scrollWidget);
        label->setPixmap(QPixmap(QString(":/images/image%1.png").arg(i)));
        scrollLayout->addWidget(label, (i - 1) / 3, (i - 1) % 3);
    }

    gridLayout->addWidget(scrollArea);

    window->setCentralWidget(centralWidget);
    window->show();

    return a.exec();
}

窗口放大缩小的程序：

#include <QApplication>
#include <QMainWindow>
#include <QHBoxLayout>
#include <QVBoxLayout>
#include <QPushButton>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QMainWindow *window = new QMainWindow;
    QWidget *centralWidget = new QWidget(window);
    QHBoxLayout *hLayout = new QHBoxLayout(centralWidget);
    QVBoxLayout *vLayout = new QVBoxLayout;
    QPushButton *button1 = new QPushButton("Button 1", centralWidget);
    QPushButton *button2 = new QPushButton("Button 2", centralWidget);

    vLayout->addWidget(button1);
    vLayout->addWidget(button2);

    hLayout->addLayout(vLayout);

    QWidget *stretchWidget = new QWidget(centralWidget);
    stretchWidget->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    hLayout->addWidget(stretchWidget);

    window->setCentralWidget(centralWidget);
    window->setMinimumSize(300, 200);
    window->show();

    return a.exec();
}

在这个示例中，我们创建了一个水平布局，其中包含两个垂直布局，每个垂直布局包含一个按钮。我们还添加了一个占位符小部件，它具有可扩展的大小策略，以便在调整窗口大小时保持两个按钮的大小不变。