【Qt流式布局改造支持任意位置插入和删除】
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文章目录
- 前言
- 一、源代码
- 二、删除代码
- 三、扩展
- 总结
前言
最近在做一个需求需要流式布局，虽然官方example里有一个流式布局范例，但是不能满足我的需求，我需要支持插入的流式布局，所以就改造了下。
一、源代码
由于我是基于官方改造的，所以就不去大张旗鼓解释了，总体就是增加一个方法：void insertWidget(int index, QWidget *widget);这里给出源代码大家可以自行研究。
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;
void insertWidget(int index, QWidget *widget);
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;
};
FlowLayout .cpp
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#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);
}
void FlowLayout::insertWidget(int index, QWidget *widget)
{
if (index < 0 || index > itemList.size()) {
index = itemList.size();
}
QLayoutItem *item = new QWidgetItem(widget);
itemList.insert(index, item);
addChildWidget(widget);
update();
}
//! [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();
}
}
//! [12]
测试代码：
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")));
flowLayout->insertWidget(flowLayout->count()-1,new QPushButton(tr("Insert")));
二、删除代码
顺便提一嘴，正常可能没有删除需求，但是如果你想删除控件的话单靠QLayout自带的removeWidget就不行了。下面就介绍删除方法，
假设你插入的QWidget叫w，这里要将w彻底回收掉才行，单纯从布局中删除是不够的，所以你插入或加入的控件指针要提前保留下来，等到从流式布局删除的时候需要用到它。
flowLayout->removeWidget(w);
w->deleteLater();
三、扩展
我最近做了一个类似于Ant的Select效果的控件,主要基于流式布局。
思路就是流式布局里插入一个输入框，当输入框获取焦点的时候弹出下拉框，下拉框可以多选。然后输入框可以搜索过滤。
可以通过点击控件外部让下拉框消失。
可以通过重复点击下拉框选项或选项流式布局里面的X按钮清除选项解决内容被篡改的问题。
总结
1、总体难度还行
2、代码从官方示例中改进而来，基本能满足我的需求。