使用代码实现QT自定义布局

```cpp
// customlayout.h
#ifndef CUSTOMLAYOUT_H
#define CUSTOMLAYOUT_H
 
#include <QLayout>
 
class CustomLayout : public QLayout
{
public:
    CustomLayout(QWidget *parent, int margin = 0, int spacing = -1);
    ~CustomLayout();
 
    void addItem(QLayoutItem *item) override;
    int count() const override;
    QLayoutItem *itemAt(int index) const override;
    QLayoutItem *takeAt(int index) override;
    QSize sizeHint() const override;
    void setGeometry(const QRect &rect) override;
 
private:
    QList<QLayoutItem *> itemList;
};
 
#endif // CUSTOMLAYOUT_H
```
 
```cpp
// customlayout.cpp
#include "customlayout.h"
 
CustomLayout::CustomLayout(QWidget *parent, int margin, int spacing)
    : QLayout(parent)
{
    setContentsMargins(margin, margin, margin, margin);
    setSpacing(spacing);
}
 
CustomLayout::~CustomLayout()
{
    QLayoutItem *item;
    while ((item = takeAt(0)))
        delete item;
}
 
void CustomLayout::addItem(QLayoutItem *item)
{
    itemList.append(item);
}
 
int CustomLayout::count() const
{
    return itemList.size();
}
 
QLayoutItem *CustomLayout::itemAt(int index) const
{
    if (index >= 0 && index < itemList.size())
        return itemList.at(index);
    return nullptr;
}
 
QLayoutItem *CustomLayout::takeAt(int index)
{
    if (index >= 0 && index < itemList.size())
        return itemList.takeAt(index);
    return nullptr;
}
 
QSize CustomLayout::sizeHint() const
{
    return QSize(200, 200);
}
 
void CustomLayout::setGeometry(const QRect &rect)
{
    QLayout::setGeometry(rect);
 
    int x = rect.x();
    int y = rect.y();
    int w = rect.width();
    int h = rect.height();
 
    for (QLayoutItem *item : itemList) {
        item->widget()->setGeometry(QRect(x, y, w, h));
    }
}
```
 
在您的Qt应用程序中，您可以使用这个自定义布局管理器来管理部件的布局。例如，在您的主窗口类中：
 
```cpp
#include "customlayout.h"
 
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    QWidget *centralWidget = new QWidget(this);
    setCentralWidget(centralWidget);
 
    CustomLayout *layout = new CustomLayout(centralWidget);
    centralWidget->setLayout(layout);
 
    QPushButton *button1 = new QPushButton("Button 1", centralWidget);
    layout->addWidget(button1);
 
    QPushButton *button2 = new QPushButton("Button 2", centralWidget);
    layout->addWidget(button2);
}
```