[TOC] ## 概述 <details> <summary> flowlayout.h</summary> ``` #ifndef FLOWLAYOUT_H #define FLOWLAYOUT_H #include <QLayout> #include <QRect> #include <QStyle> //! [0] class FlowLayout : public QLayout { public: explicit FlowLayout(QWidget *parent, int margin = -1, int hSpacing = -1, int vSpacing = -1); explicit FlowLayout(int margin = -1, int hSpacing = -1, int vSpacing = -1); ~FlowLayout(); void addItem(QLayoutItem *item) override; int horizontalSpacing() const; int verticalSpacing() const; Qt::Orientations expandingDirections() const override; bool hasHeightForWidth() const override; int heightForWidth(int) const override; int count() const override; QLayoutItem *itemAt(int index) const override; QSize minimumSize() const override; void setGeometry(const QRect &rect) override; QSize sizeHint() const override; QLayoutItem *takeAt(int index) override; private: int doLayout(const QRect &rect, bool testOnly) const; int smartSpacing(QStyle::PixelMetric pm) const; QList<QLayoutItem *> itemList; int m_hSpace; int m_vSpace; }; //! [0] #endif // FLOWLAYOUT_H ``` </details> <br /> <details> <summary> flowlayout.cpp</summary> ``` #include <QtWidgets> #include "flowlayout.h" //! [1] FlowLayout::FlowLayout(QWidget *parent, int margin, int hSpacing, int vSpacing) : QLayout(parent), m_hSpace(hSpacing), m_vSpace(vSpacing) { setContentsMargins(margin, margin, margin, margin); } FlowLayout::FlowLayout(int margin, int hSpacing, int vSpacing) : m_hSpace(hSpacing), m_vSpace(vSpacing) { setContentsMargins(margin, margin, margin, margin); } //! [1] //! [2] FlowLayout::~FlowLayout() { QLayoutItem *item; while ((item = takeAt(0))) delete item; } //! [2] //! [3] void FlowLayout::addItem(QLayoutItem *item) { itemList.append(item); } //! [3] //! [4] int FlowLayout::horizontalSpacing() const { if (m_hSpace >= 0) { return m_hSpace; } else { return smartSpacing(QStyle::PM_LayoutHorizontalSpacing); } } int FlowLayout::verticalSpacing() const { if (m_vSpace >= 0) { return m_vSpace; } else { return smartSpacing(QStyle::PM_LayoutVerticalSpacing); } } //! [4] //! [5] int FlowLayout::count() const { return itemList.size(); } QLayoutItem *FlowLayout::itemAt(int index) const { return itemList.value(index); } QLayoutItem *FlowLayout::takeAt(int index) { if (index >= 0 && index < itemList.size()) return itemList.takeAt(index); return nullptr; } //! [5] //! [6] Qt::Orientations FlowLayout::expandingDirections() const { return { }; } //! [6] //! [7] bool FlowLayout::hasHeightForWidth() const { return true; } int FlowLayout::heightForWidth(int width) const { int height = doLayout(QRect(0, 0, width, 0), true); return height; } //! [7] //! [8] void FlowLayout::setGeometry(const QRect &rect) { QLayout::setGeometry(rect); doLayout(rect, false); } QSize FlowLayout::sizeHint() const { return minimumSize(); } QSize FlowLayout::minimumSize() const { QSize size; for (const QLayoutItem *item : qAsConst(itemList)) size = size.expandedTo(item->minimumSize()); const QMargins margins = contentsMargins(); size += QSize(margins.left() + margins.right(), margins.top() + margins.bottom()); return size; } //! [8] //! [9] int FlowLayout::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; //! [9] //! [10] for (QLayoutItem *item : qAsConst(itemList)) { const 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); //! [10] //! [11] 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; } //! [11] //! [12] int FlowLayout::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, nullptr, pw); } else { return static_cast<QLayout *>(parent)->spacing(); } } ``` </details> <br /> 使用 ``` FlowLayout *flowLayout = new FlowLayout; flowLayout->addWidget(new QPushButton(tr("Short"))); flowLayout->addWidget(new QPushButton(tr("Longer"))); flowLayout->addWidget(new QPushButton(tr("Different text"))); flowLayout->addWidget(new QPushButton(tr("More text"))); flowLayout->addWidget(new QPushButton(tr("Even longer button text"))); // 如果嵌入到父组件中,调节父组件,不影响的组件,所以不会生效 //QWidget *w = new QWidget(this); QWidget *w = new QWidget(); w->setLayout(flowLayout); w->show(); ```