Qt之流式布局QFlowLayout

╰+攻爆jí腚メ 2022-12-26 08:17 160阅读 0赞

Qt没有像网页那种能根据窗口大小改变的布局，但是我们可以利用继承QLayout 自己编写！！！

# 环境： #

QtCreator 5.14.2

# 代码： #

qflowlayout.h：

#ifndef QFLOWLAYOUT_H
    #define QFLOWLAYOUT_H
    
    #include <QWidget>
    #include <QLayout>
    #include <QRect>
    #include <QStyle>
    
    #include <QLayout>
    #include <QRect>
    #include <QStyle>
    class QFlowLayout : public QLayout
    {
    public:
        explicit QFlowLayout(QWidget *parent, int margin = -1, int hSpacing = -1, int vSpacing = -1);
        explicit QFlowLayout(int margin = -1, int hSpacing = -1, int vSpacing = -1);
        ~QFlowLayout();
    
        void addItem(QLayoutItem *item) Q_DECL_OVERRIDE;
        int horizontalSpacing() const;
        int verticalSpacing() const;
        Qt::Orientations expandingDirections() const Q_DECL_OVERRIDE;
        bool hasHeightForWidth() const Q_DECL_OVERRIDE;
        int heightForWidth(int) const Q_DECL_OVERRIDE;
        int count() const Q_DECL_OVERRIDE;
        QLayoutItem *itemAt(int index) const Q_DECL_OVERRIDE;
        QSize minimumSize() const Q_DECL_OVERRIDE;
        void setGeometry(const QRect &rect) Q_DECL_OVERRIDE;
        QSize sizeHint() const Q_DECL_OVERRIDE;
        QLayoutItem *takeAt(int index) Q_DECL_OVERRIDE;
    
    private:
        int doLayout(const QRect &rect, bool testOnly) const;
        int smartSpacing(QStyle::PixelMetric pm) const;
    
    private:
        QList<QLayoutItem *> x_itemList;
        int x_hSpace;
        int x_vSpace;
    };
    
    #endif // QFLOWLAYOUT_H

**qflowlayout.cpp：**

#include "qflowlayout.h"
    
    #include <algorithm>
    #include <QWidget>
    
    QFlowLayout::QFlowLayout(QWidget *parent, int margin, int hSpacing, int vSpacing)
        : QLayout(parent),
        x_hSpace(hSpacing),
        x_vSpace(vSpacing)
    {
        setContentsMargins(margin, margin, margin, margin);
    }
    
    QFlowLayout::QFlowLayout(int margin, int hSpacing, int vSpacing)
        : x_hSpace(hSpacing),
        x_vSpace(vSpacing)
    {
        setContentsMargins(margin, margin, margin, margin);
    }
    
    QFlowLayout::~QFlowLayout()
    {
        QLayoutItem *item;
        while ((item = takeAt(0)))
            delete item;
    }
    
    void QFlowLayout::addItem(QLayoutItem *item)
    {
        x_itemList.append(item);
    }
    
    int QFlowLayout::horizontalSpacing() const
    {
        if (x_hSpace >= 0)
        {
            return x_hSpace;
        }
        else
        {
            return smartSpacing(QStyle::PM_LayoutHorizontalSpacing);
        }
    }
    
    int QFlowLayout::verticalSpacing() const
    {
        if (x_vSpace >= 0) {
            return x_vSpace;
        }
        else {
            return smartSpacing(QStyle::PM_LayoutVerticalSpacing);
        }
    }
    
    int QFlowLayout::count() const
    {
        return x_itemList.size();
    }
    
    QLayoutItem *QFlowLayout::itemAt(int index) const
    {
        return x_itemList.value(index);
    }
    
    QLayoutItem *QFlowLayout::takeAt(int index)
    {
        if (index >= 0 && index < x_itemList.size())
            return x_itemList.takeAt(index);
        else
            return 0;
    }
    
    Qt::Orientations QFlowLayout::expandingDirections() const
    {
        return 0;
    }
    
    bool QFlowLayout::hasHeightForWidth() const
    {
        return true;
    }
    
    int QFlowLayout::heightForWidth(int width) const
    {
        int height = doLayout(QRect(0, 0, width, 0), true);
        return height;
    }
    
    void QFlowLayout::setGeometry(const QRect &rect)
    {
        QLayout::setGeometry(rect);
        doLayout(rect, false);
    }
    
    QSize QFlowLayout::sizeHint() const
    {
        return minimumSize();
    }
    
    QSize QFlowLayout::minimumSize() const
    {
        QSize size;
        QLayoutItem *item;
        foreach(item, x_itemList)
            size = size.expandedTo(item->minimumSize());
    
        size += QSize(2 * margin(), 2 * margin());
        return size;
    }
    
    int QFlowLayout::doLayout(const QRect &rect, bool testOnly) const
    {
        int left, top, right, bottom;
        getContentsMargins(&left, &top, &right, &bottom);
        QRect effectiveRect = rect.adjusted(+left, +top, -right, -bottom);
        int x = effectiveRect.x();
        int y = effectiveRect.y();
        int lineHeight = 0;
    
        QLayoutItem *item;
        foreach(item, x_itemList) {
            QWidget *wid = item->widget();
            int spaceX = horizontalSpacing();
            if (spaceX == -1)
                spaceX = wid->style()->layoutSpacing(
                QSizePolicy::PushButton, QSizePolicy::PushButton, Qt::Horizontal);
            int spaceY = verticalSpacing();
            if (spaceY == -1)
                spaceY = wid->style()->layoutSpacing(
                QSizePolicy::PushButton, QSizePolicy::PushButton, Qt::Vertical);
    
            int nextX = x + item->sizeHint().width() + spaceX;
            if (nextX - spaceX > effectiveRect.right() && lineHeight > 0) {
                x = effectiveRect.x();
                y = y + lineHeight + spaceY;
                nextX = x + item->sizeHint().width() + spaceX;
                lineHeight = 0;
            }
    
            if (!testOnly)
                item->setGeometry(QRect(QPoint(x, y), item->sizeHint()));
    
            x = nextX;
            lineHeight = qMax(lineHeight, item->sizeHint().height());
        }
        return y + lineHeight - rect.y() + bottom;
    }
    
    int QFlowLayout::smartSpacing(QStyle::PixelMetric pm) const
    {
        QObject *parent = this->parent();
        if (!parent) {
            return -1;
        }
        else if (parent->isWidgetType()) {
            QWidget *pw = static_cast<QWidget *>(parent);
            return pw->style()->pixelMetric(pm, 0, pw);
        }
        else {
            return static_cast<QLayout *>(parent)->spacing();
        }
    }

**widget.cpp：**

#include "widget.h"
    
    Widget::Widget(QWidget *parent)
        : QWidget(parent)
    {
        setMaximumSize(600,500);
    
       QFlowLayout * flowLayout = new QFlowLayout(this);
    
       flowLayout->addWidget(new QPushButton("1"));
       flowLayout ->addWidget(new QPushButton("2"));
       flowLayout ->addWidget(new QPushButton("3"));
       flowLayout ->addWidget(new QPushButton("4444444444444444"));
       flowLayout ->addWidget(new QPushButton("55"));
       flowLayout ->addWidget(new QPushButton("6"));
    
    }
    
    Widget::~Widget()
    {
    }
    
    void Widget::dealClick(bool flag){
        qDebug() << flag;
        if (!flag){
            lineEdit->undo();
        }
    }
    
    void Widget::listChildrens(QWidget * widget){
        QObjectList objectList = widget->children();
    
        for (int i=0;i<objectList.size();i++){
            qDebug() << objectList[i]->objectName();
            qDebug() << objectList[i]->metaObject()->className();
    
            listChildrens(qobject_cast<QWidget *>(objectList[i]));
        }
    }

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