简述

QBorderLayout，顾名思义-边框布局，实现了排列子控件包围中央区域的布局。

具体实现要求不再赘述，请参考前几节内容。

实现

QBorderLayout主要采用QLayout和QWidgetItem实现，而窗口使用了QWidget，中央窗体使用QTextBrowser，四周以QLabel排列。

效果

源码

QBorderLayout.h

#ifndef QBORDERLAYOUT_H

#define QBORDERLAYOUT_H

#include <QLayout>

#include <QRect>

class QBorderLayout : public QLayout

{

public:

    enum Position {West, North, South, East, Center};

    explicit QBorderLayout(QWidget *parent, int margin = 0, int spacing = -1);

    QBorderLayout(int spacing = -1);

    ~QBorderLayout();

    void addItem(QLayoutItem *item) Q_DECL_OVERRIDE;

    void addWidget(QWidget *widget, Position position);

    Qt::Orientations expandingDirections() const Q_DECL_OVERRIDE;

    bool hasHeightForWidth() 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;

    void add(QLayoutItem *item, Position position);

private:

    struct ItemWrapper

    {

        ItemWrapper(QLayoutItem *i, Position p) {

            item = i;

            position = p;

        }

        QLayoutItem *item;

        Position position;

    };

    enum SizeType { MinimumSize, SizeHint };

    QSize calculateSize(SizeType sizeType) const;

    QList<ItemWrapper *> list;

};

#endif // QBORDERLAYOUT_H

QBorderLayout.cpp

#include "QBorderLayout.h"

QBorderLayout::QBorderLayout(QWidget *parent, int margin, int spacing)

    : QLayout(parent)

{

    setMargin(margin);

    setSpacing(spacing);

}

QBorderLayout::QBorderLayout(int spacing)

{

    setSpacing(spacing);

}

QBorderLayout::~QBorderLayout()

{

    QLayoutItem *l;

    while ((l = takeAt(0)))

        delete l;

}

void QBorderLayout::addItem(QLayoutItem *item)

{

    add(item, West);

}

void QBorderLayout::addWidget(QWidget *widget, Position position)

{

    add(new QWidgetItem(widget), position);

}

Qt::Orientations QBorderLayout::expandingDirections() const

{

    return Qt::Horizontal | Qt::Vertical;

}

bool QBorderLayout::hasHeightForWidth() const

{

    return false;

}

int QBorderLayout::count() const

{

    return list.size();

}

QLayoutItem *QBorderLayout::itemAt(int index) const

{

    ItemWrapper *wrapper = list.value(index);

    if (wrapper)

        return wrapper->item;

    else

        return 0;

}

QSize QBorderLayout::minimumSize() const

{

    return calculateSize(MinimumSize);

}

void QBorderLayout::setGeometry(const QRect &rect)

{

    ItemWrapper *center = 0;

    int eastWidth = 0;

    int westWidth = 0;

    int northHeight = 0;

    int southHeight = 0;

    int centerHeight = 0;

    int i;

    QLayout::setGeometry(rect);

    for (i = 0; i < list.size(); ++i) {

        ItemWrapper *wrapper = list.at(i);

        QLayoutItem *item = wrapper->item;

        Position position = wrapper->position;

        if (position == North) {

            item->setGeometry(QRect(rect.x(), northHeight, rect.width(),

                                    item->sizeHint().height()));

            northHeight += item->geometry().height() + spacing();

        } else if (position == South) {

            item->setGeometry(QRect(item->geometry().x(),

                                    item->geometry().y(), rect.width(),

                                    item->sizeHint().height()));

            southHeight += item->geometry().height() + spacing();

            item->setGeometry(QRect(rect.x(),

                              rect.y() + rect.height() - southHeight + spacing(),

                              item->geometry().width(),

                              item->geometry().height()));

        } else if (position == Center) {

            center = wrapper;

        }

    }

    centerHeight = rect.height() - northHeight - southHeight;

    for (i = 0; i < list.size(); ++i) {

        ItemWrapper *wrapper = list.at(i);

        QLayoutItem *item = wrapper->item;

        Position position = wrapper->position;

        if (position == West) {

            item->setGeometry(QRect(rect.x() + westWidth, northHeight,

                                    item->sizeHint().width(), centerHeight));

            westWidth += item->geometry().width() + spacing();

        } else if (position == East) {

            item->setGeometry(QRect(item->geometry().x(), item->geometry().y(),

                                    item->sizeHint().width(), centerHeight));

            eastWidth += item->geometry().width() + spacing();

            item->setGeometry(QRect(

                              rect.x() + rect.width() - eastWidth + spacing(),

                              northHeight, item->geometry().width(),

                              item->geometry().height()));

        }

    }

    if (center)

        center->item->setGeometry(QRect(westWidth, northHeight,

                                        rect.width() - eastWidth - westWidth,

                                        centerHeight));

}

QSize QBorderLayout::sizeHint() const

{

    return calculateSize(SizeHint);

}

QLayoutItem *QBorderLayout::takeAt(int index)

{

    if (index >= 0 && index < list.size()) {

        ItemWrapper *layoutStruct = list.takeAt(index);

        return layoutStruct->item;

    }

    return 0;

}

void QBorderLayout::add(QLayoutItem *item, Position position)

{

    list.append(new ItemWrapper(item, position));

}

QSize QBorderLayout::calculateSize(SizeType sizeType) const

{

    QSize totalSize;

    for (int i = 0; i < list.size(); ++i) {

        ItemWrapper *wrapper = list.at(i);

        Position position = wrapper->position;

        QSize itemSize;

        if (sizeType == MinimumSize)

            itemSize = wrapper->item->minimumSize();

        else // (sizeType == SizeHint)

            itemSize = wrapper->item->sizeHint();

        if (position == North || position == South || position == Center)

            totalSize.rheight() += itemSize.height();

        if (position == West || position == East || position == Center)

            totalSize.rwidth() += itemSize.width();

    }

    return totalSize;

}

使用

中央窗体使用QTextBrowser，四周以QLabel排列开来。

QTextBrowser *pCentralWidget = new QTextBrowser(this);

pCentralWidget->setPlainText(tr("Central Widget"));

QBorderLayout *pLayout = new QBorderLayout();

pLayout->addWidget(pCentralWidget, QBorderLayout::Center);

pLayout->addWidget(createLabel("North"), QBorderLayout::North);

pLayout->addWidget(createLabel("West"), QBorderLayout::West);

pLayout->addWidget(createLabel("East 1"), QBorderLayout::East);

pLayout->addWidget(createLabel("East 2") , QBorderLayout::East);

pLayout->addWidget(createLabel("South"), QBorderLayout::South);

setLayout(pLayout);

QLabel *MainWindow::createLabel(const QString &text)

{

    QLabel *pLabel = new QLabel(this);

    pLabel->setText(text);

    pLabel->setFrameStyle(QFrame::Box | QFrame::Raised);

    return pLabel;

}