Qt 官方demo Basic Drawing 详解

其他 2020-04-18 10:58:52 阅读次数: 0

前言:

来看一个 qt 自己的demo ，然后细细的看下他们的代码 能学到一些新知识
比如 tr("&S") 加这个& 代表什么意思
setBuddy() 函数的作用 等等

入口:

在这里插入图片描述

效果图:

在这里插入图片描述

#####1. 先看下 整个的项目结构:
在这里插入图片描述

两个 类
renderarea
window
2个资源图片

还是很简单的一个小demo

2.看main 函数

在这里插入图片描述

很简单 上来先 初始化 资源

然后 实例化 window 类
在这里插入图片描述

在这里插入图片描述

window 类结构

window.h

#ifndef WINDOW_H
#define WINDOW_H

#include <QWidget>

QT_BEGIN_NAMESPACE
class QCheckBox;
class QComboBox;
class QLabel;
class QSpinBox;
QT_END_NAMESPACE
class RenderArea;

//! [0]
class Window : public QWidget
{
    Q_OBJECT

public:
    Window();

private slots:
    void shapeChanged();
    void penChanged();
    void brushChanged();

private:
    RenderArea *renderArea;
    QLabel *shapeLabel;
    QLabel *penWidthLabel;
    QLabel *penStyleLabel;
    QLabel *penCapLabel;
    QLabel *penJoinLabel;
    QLabel *brushStyleLabel;
    QLabel *otherOptionsLabel;
    QComboBox *shapeComboBox;
    QSpinBox *penWidthSpinBox;
    QComboBox *penStyleComboBox;
    QComboBox *penCapComboBox;
    QComboBox *penJoinComboBox;
    QComboBox *brushStyleComboBox;
    QCheckBox *antialiasingCheckBox;
    QCheckBox *transformationsCheckBox;
};
//! [0]

#endif // WINDOW_H

window.cpp

#include "renderarea.h"
#include "window.h"

#include <QtWidgets>

//! [0]
const int IdRole = Qt::UserRole;
//! [0]

//! [1]
Window::Window()
{
    renderArea = new RenderArea;

    shapeComboBox = new QComboBox;
    shapeComboBox->addItem(tr("Polygon"), RenderArea::Polygon);
    shapeComboBox->addItem(tr("Rectangle"), RenderArea::Rect);
    shapeComboBox->addItem(tr("Rounded Rectangle"), RenderArea::RoundedRect);
    shapeComboBox->addItem(tr("Ellipse"), RenderArea::Ellipse);
    shapeComboBox->addItem(tr("Pie"), RenderArea::Pie);
    shapeComboBox->addItem(tr("Chord"), RenderArea::Chord);
    shapeComboBox->addItem(tr("Path"), RenderArea::Path);
    shapeComboBox->addItem(tr("Line"), RenderArea::Line);
    shapeComboBox->addItem(tr("Polyline"), RenderArea::Polyline);
    shapeComboBox->addItem(tr("Arc"), RenderArea::Arc);
    shapeComboBox->addItem(tr("Points"), RenderArea::Points);
    shapeComboBox->addItem(tr("Text"), RenderArea::Text);
    shapeComboBox->addItem(tr("Pixmap"), RenderArea::Pixmap);

    shapeLabel = new QLabel(tr("&Shape:"));
    shapeLabel->setBuddy(shapeComboBox);
//! [1]

//! [2]
    penWidthSpinBox = new QSpinBox;
    penWidthSpinBox->setRange(0, 20);
    penWidthSpinBox->setSpecialValueText(tr("0 (cosmetic pen)"));

    penWidthLabel = new QLabel(tr("&Pen Width:"));
    penWidthLabel->setBuddy(penWidthSpinBox);
//! [2]

//! [3]
    penStyleComboBox = new QComboBox;
    penStyleComboBox->addItem(tr("Solid"), static_cast<int>(Qt::SolidLine));
    penStyleComboBox->addItem(tr("Dash"), static_cast<int>(Qt::DashLine));
    penStyleComboBox->addItem(tr("Dot"), static_cast<int>(Qt::DotLine));
    penStyleComboBox->addItem(tr("Dash Dot"), static_cast<int>(Qt::DashDotLine));
    penStyleComboBox->addItem(tr("Dash Dot Dot"), static_cast<int>(Qt::DashDotDotLine));
    penStyleComboBox->addItem(tr("None"), static_cast<int>(Qt::NoPen));

    penStyleLabel = new QLabel(tr("&Pen Style:"));
    penStyleLabel->setBuddy(penStyleComboBox);

    penCapComboBox = new QComboBox;
    penCapComboBox->addItem(tr("Flat"), Qt::FlatCap);
    penCapComboBox->addItem(tr("Square"), Qt::SquareCap);
    penCapComboBox->addItem(tr("Round"), Qt::RoundCap);

    penCapLabel = new QLabel(tr("Pen &Cap:"));
    penCapLabel->setBuddy(penCapComboBox);

    penJoinComboBox = new QComboBox;
    penJoinComboBox->addItem(tr("Miter"), Qt::MiterJoin);
    penJoinComboBox->addItem(tr("Bevel"), Qt::BevelJoin);
    penJoinComboBox->addItem(tr("Round"), Qt::RoundJoin);

    penJoinLabel = new QLabel(tr("Pen &Join:"));
    penJoinLabel->setBuddy(penJoinComboBox);
//! [3]

//! [4]
    brushStyleComboBox = new QComboBox;
    brushStyleComboBox->addItem(tr("Linear Gradient"),
            static_cast<int>(Qt::LinearGradientPattern));
    brushStyleComboBox->addItem(tr("Radial Gradient"),
            static_cast<int>(Qt::RadialGradientPattern));
    brushStyleComboBox->addItem(tr("Conical Gradient"),
            static_cast<int>(Qt::ConicalGradientPattern));
    brushStyleComboBox->addItem(tr("Texture"), static_cast<int>(Qt::TexturePattern));
    brushStyleComboBox->addItem(tr("Solid"), static_cast<int>(Qt::SolidPattern));
    brushStyleComboBox->addItem(tr("Horizontal"), static_cast<int>(Qt::HorPattern));
    brushStyleComboBox->addItem(tr("Vertical"), static_cast<int>(Qt::VerPattern));
    brushStyleComboBox->addItem(tr("Cross"), static_cast<int>(Qt::CrossPattern));
    brushStyleComboBox->addItem(tr("Backward Diagonal"), static_cast<int>(Qt::BDiagPattern));
    brushStyleComboBox->addItem(tr("Forward Diagonal"), static_cast<int>(Qt::FDiagPattern));
    brushStyleComboBox->addItem(tr("Diagonal Cross"), static_cast<int>(Qt::DiagCrossPattern));
    brushStyleComboBox->addItem(tr("Dense 1"), static_cast<int>(Qt::Dense1Pattern));
    brushStyleComboBox->addItem(tr("Dense 2"), static_cast<int>(Qt::Dense2Pattern));
    brushStyleComboBox->addItem(tr("Dense 3"), static_cast<int>(Qt::Dense3Pattern));
    brushStyleComboBox->addItem(tr("Dense 4"), static_cast<int>(Qt::Dense4Pattern));
    brushStyleComboBox->addItem(tr("Dense 5"), static_cast<int>(Qt::Dense5Pattern));
    brushStyleComboBox->addItem(tr("Dense 6"), static_cast<int>(Qt::Dense6Pattern));
    brushStyleComboBox->addItem(tr("Dense 7"), static_cast<int>(Qt::Dense7Pattern));
    brushStyleComboBox->addItem(tr("None"), static_cast<int>(Qt::NoBrush));

    brushStyleLabel = new QLabel(tr("&Brush:"));
    brushStyleLabel->setBuddy(brushStyleComboBox);
//! [4]

//! [5]
    otherOptionsLabel = new QLabel(tr("Options:"));
//! [5] //! [6]
    antialiasingCheckBox = new QCheckBox(tr("&Antialiasing"));
//! [6] //! [7]
    transformationsCheckBox = new QCheckBox(tr("&Transformations"));
//! [7]

//! [8]
    connect(shapeComboBox, SIGNAL(activated(int)),
            this, SLOT(shapeChanged()));
    connect(penWidthSpinBox, SIGNAL(valueChanged(int)),
            this, SLOT(penChanged()));
    connect(penStyleComboBox, SIGNAL(activated(int)),
            this, SLOT(penChanged()));
    connect(penCapComboBox, SIGNAL(activated(int)),
            this, SLOT(penChanged()));
    connect(penJoinComboBox, SIGNAL(activated(int)),
            this, SLOT(penChanged()));
    connect(brushStyleComboBox, SIGNAL(activated(int)),
            this, SLOT(brushChanged()));
    connect(antialiasingCheckBox, SIGNAL(toggled(bool)),
            renderArea, SLOT(setAntialiased(bool)));
    connect(transformationsCheckBox, SIGNAL(toggled(bool)),
            renderArea, SLOT(setTransformed(bool)));
//! [8]

//! [9]
    QGridLayout *mainLayout = new QGridLayout;
//! [9] //! [10]
    mainLayout->setColumnStretch(0, 1);
    mainLayout->setColumnStretch(3, 1);
    mainLayout->addWidget(renderArea, 0, 0, 1, 4);
    mainLayout->addWidget(shapeLabel, 2, 0, Qt::AlignRight);
    mainLayout->addWidget(shapeComboBox, 2, 1);
    mainLayout->addWidget(penWidthLabel, 3, 0, Qt::AlignRight);
    mainLayout->addWidget(penWidthSpinBox, 3, 1);
    mainLayout->addWidget(penStyleLabel, 4, 0, Qt::AlignRight);
    mainLayout->addWidget(penStyleComboBox, 4, 1);
    mainLayout->addWidget(penCapLabel, 3, 2, Qt::AlignRight);
    mainLayout->addWidget(penCapComboBox, 3, 3);
    mainLayout->addWidget(penJoinLabel, 2, 2, Qt::AlignRight);
    mainLayout->addWidget(penJoinComboBox, 2, 3);
    mainLayout->addWidget(brushStyleLabel, 4, 2, Qt::AlignRight);
    mainLayout->addWidget(brushStyleComboBox, 4, 3);
    mainLayout->addWidget(otherOptionsLabel, 5, 0, Qt::AlignRight);
    mainLayout->addWidget(antialiasingCheckBox, 5, 1, 1, 1, Qt::AlignRight);
    mainLayout->addWidget(transformationsCheckBox, 5, 2, 1, 2, Qt::AlignRight);
    setLayout(mainLayout);

    shapeChanged();
    penChanged();
    brushChanged();
    antialiasingCheckBox->setChecked(true);

    setWindowTitle(tr("Basic Drawing"));
}
//! [10]

//! [11]
void Window::shapeChanged()
{
    RenderArea::Shape shape = RenderArea::Shape(shapeComboBox->itemData(
            shapeComboBox->currentIndex(), IdRole).toInt());
    renderArea->setShape(shape);
}
//! [11]

//! [12]
void Window::penChanged()
{
    int width = penWidthSpinBox->value();
    Qt::PenStyle style = Qt::PenStyle(penStyleComboBox->itemData(
            penStyleComboBox->currentIndex(), IdRole).toInt());
    Qt::PenCapStyle cap = Qt::PenCapStyle(penCapComboBox->itemData(
            penCapComboBox->currentIndex(), IdRole).toInt());
    Qt::PenJoinStyle join = Qt::PenJoinStyle(penJoinComboBox->itemData(
            penJoinComboBox->currentIndex(), IdRole).toInt());

    renderArea->setPen(QPen(Qt::blue, width, style, cap, join));
}
//! [12]

//! [13]
void Window::brushChanged()
{
    Qt::BrushStyle style = Qt::BrushStyle(brushStyleComboBox->itemData(
//! [13]
            brushStyleComboBox->currentIndex(), IdRole).toInt());

//! [14]
    if (style == Qt::LinearGradientPattern) {
        QLinearGradient linearGradient(0, 0, 100, 100);
        linearGradient.setColorAt(0.0, Qt::white);
        linearGradient.setColorAt(0.2, Qt::green);
        linearGradient.setColorAt(1.0, Qt::black);
        renderArea->setBrush(linearGradient);
//! [14] //! [15]
    } else if (style == Qt::RadialGradientPattern) {
        QRadialGradient radialGradient(50, 50, 50, 70, 70);
        radialGradient.setColorAt(0.0, Qt::white);
        radialGradient.setColorAt(0.2, Qt::green);
        radialGradient.setColorAt(1.0, Qt::black);
        renderArea->setBrush(radialGradient);
    } else if (style == Qt::ConicalGradientPattern) {
        QConicalGradient conicalGradient(50, 50, 150);
        conicalGradient.setColorAt(0.0, Qt::white);
        conicalGradient.setColorAt(0.2, Qt::green);
        conicalGradient.setColorAt(1.0, Qt::black);
        renderArea->setBrush(conicalGradient);
//! [15] //! [16]
    } else if (style == Qt::TexturePattern) {
        renderArea->setBrush(QBrush(QPixmap(":/images/brick.png")));
//! [16] //! [17]
    } else {
        renderArea->setBrush(QBrush(Qt::green, style));
    }
}
//! [17]

他的界面是代码写的 然后 都是一些基本的控件 除了 类RenderArea 这个暂时不管 先看构造函数

window 构造函数

在这里插入图片描述
shape 的combox additem 用的重载的 可以写QVariant 类型的 这里是枚举
在这里插入图片描述

    shapeLabel = new QLabel(tr("&Shape:"));
  shapeLabel->setBuddy(shapeComboBox);

tr("&") 和 setBuddy（） 干啥的 ？

我也没见过啊 我去查了一下 这俩是配合使用的

shapeLabel 的快捷键是 “ALT+w”，按下快捷键时，输入焦点自动跳到label的buddy shapeComboBox上。
个人理解：这段代码shapeLabel->setBuddy(shapeComboBox);是设置行编辑器作为label 的伙伴，所谓伙伴（buddy）就是就是一个窗口部件，按上面英文就是当你按下快捷键的时候，这个快捷键是在label上标明的，然后焦点就会移动到label的小伙伴身上

QLabel(tr("&Shape:")); 就不是 ALT + W 了 是ALT + &后面的第一个字母
也就是 ALT + S 就把焦点 跳到 Combox 上面

效果图:

在这里插入图片描述

在这里插入图片描述
这里 还是和上面一样 重载的 把类型转为了 int

是为了配合下面的信号槽使用
在这里插入图片描述
在这里插入图片描述

在这里插入图片描述

这样写起来方便,不需要在根据所选择的条目不同 发送不同的信号

这点也学到了 以后

基本上这个类 就结束了 就是些控件 初始化 然后 布局了，
咱们开始看 下一个 绘图类

Renderarea 类结构

renderarea.h

#ifndef RENDERAREA_H
#define RENDERAREA_H

#include <QBrush>
#include <QPen>
#include <QPixmap>
#include <QWidget>

//! [0]
class RenderArea : public QWidget
{
    Q_OBJECT

public:
    enum Shape { Line, Points, Polyline, Polygon, Rect, RoundedRect, Ellipse, Arc,
                 Chord, Pie, Path, Text, Pixmap };

    RenderArea(QWidget *parent = 0);

    QSize minimumSizeHint() const override;
    QSize sizeHint() const override;

public slots:
    void setShape(Shape shape);
    void setPen(const QPen &pen);
    void setBrush(const QBrush &brush);
    void setAntialiased(bool antialiased);
    void setTransformed(bool transformed);

protected:
    void paintEvent(QPaintEvent *event) override;

private:
    Shape shape;
    QPen pen;
    QBrush brush;
    bool antialiased;
    bool transformed;
    QPixmap pixmap;
};
//! [0]

#endif // RENDERAREA_H

renderarea.cpp

#include "renderarea.h"

#include <QPainter>

//! [0]
RenderArea::RenderArea(QWidget *parent)
    : QWidget(parent)
{
    shape = Polygon;
    antialiased = false;
    transformed = false;
    pixmap.load(":/images/qt-logo.png");

    setBackgroundRole(QPalette::Base);
    setAutoFillBackground(true);
}
//! [0]

//! [1]
QSize RenderArea::minimumSizeHint() const
{
    return QSize(100, 100);
}
//! [1]

//! [2]
QSize RenderArea::sizeHint() const
{
    return QSize(400, 200);
}
//! [2]

//! [3]
void RenderArea::setShape(Shape shape)
{
    this->shape = shape;
    update();
}
//! [3]

//! [4]
void RenderArea::setPen(const QPen &pen)
{
    this->pen = pen;
    update();
}
//! [4]

//! [5]
void RenderArea::setBrush(const QBrush &brush)
{
    this->brush = brush;
    update();
}
//! [5]

//! [6]
void RenderArea::setAntialiased(bool antialiased)
{
    this->antialiased = antialiased;
    update();
}
//! [6]

//! [7]
void RenderArea::setTransformed(bool transformed)
{
    this->transformed = transformed;
    update();
}
//! [7]

//! [8]
void RenderArea::paintEvent(QPaintEvent * /* event */)
{
    static const QPoint points[4] = {
        QPoint(10, 80),
        QPoint(20, 10),
        QPoint(80, 30),
        QPoint(90, 70)
    };

    QRect rect(10, 20, 80, 60);

    QPainterPath path;
    path.moveTo(20, 80);
    path.lineTo(20, 30);
    path.cubicTo(80, 0, 50, 50, 80, 80);

    int startAngle = 20 * 16;
    int arcLength = 120 * 16;
//! [8]

//! [9]
    QPainter painter(this);
    painter.setPen(pen);
    painter.setBrush(brush);
    if (antialiased)
        painter.setRenderHint(QPainter::Antialiasing, true);
//! [9]

//! [10]
    for (int x = 0; x < width(); x += 100) {
        for (int y = 0; y < height(); y += 100) {
            painter.save();
            painter.translate(x, y);
//! [10] //! [11]
            if (transformed) {
                painter.translate(50, 50);
                painter.rotate(60.0);
                painter.scale(0.6, 0.9);
                painter.translate(-50, -50);
            }
//! [11]

//! [12]
            switch (shape) {
            case Line:
                painter.drawLine(rect.bottomLeft(), rect.topRight());
                break;
            case Points:
                painter.drawPoints(points, 4);
                break;
            case Polyline:
                painter.drawPolyline(points, 4);
                break;
            case Polygon:
                painter.drawPolygon(points, 4);
                break;
            case Rect:
                painter.drawRect(rect);
                break;
            case RoundedRect:
                painter.drawRoundedRect(rect, 25, 25, Qt::RelativeSize);
                break;
            case Ellipse:
                painter.drawEllipse(rect);
                break;
            case Arc:
                painter.drawArc(rect, startAngle, arcLength);
                break;
            case Chord:
                painter.drawChord(rect, startAngle, arcLength);
                break;
            case Pie:
                painter.drawPie(rect, startAngle, arcLength);
                break;
            case Path:
                painter.drawPath(path);
                break;
            case Text:
                painter.drawText(rect,
                                 Qt::AlignCenter,
                                 tr("Qt by\nThe Qt Company"));
                break;
            case Pixmap:
                painter.drawPixmap(10, 10, pixmap);
            }
//! [12] //! [13]
            painter.restore();
        }
    }

    painter.setRenderHint(QPainter::Antialiasing, false);
    painter.setPen(palette().dark().color());
    painter.setBrush(Qt::NoBrush);
    painter.drawRect(QRect(0, 0, width() - 1, height() - 1));
}
//! [13]

继承了 qwidget

写了一个枚举 代表 某些形状

重载了 父类的一些函数
在这里插入图片描述

加 override 的好处就是 显示的代表重载 然后编译器会找父类的这个函数 如果找不到就报错
如果不加 override ,如果写错了个字母 就不是重载了 是实现了 自己的新函数

这类里没有啥 咱们只看 PaintEvent

PaintEvent

void RenderArea::paintEvent(QPaintEvent * /* event */)
{
    static const QPoint points[4] = {
        QPoint(10, 80),
        QPoint(20, 10),
        QPoint(80, 30),
        QPoint(90, 70)
    };

    QRect rect(10, 20, 80, 60);

    QPainterPath path;
    path.moveTo(20, 80);
    path.lineTo(20, 30);
    path.cubicTo(80, 0, 50, 50, 80, 80);

    int startAngle = 20 * 16;
    int arcLength = 120 * 16;
//! [8]

//! [9]
    QPainter painter(this);
    painter.setPen(pen);
    painter.setBrush(brush);
    if (antialiased)
        painter.setRenderHint(QPainter::Antialiasing, true);
//! [9]

//! [10]
    for (int x = 0; x < width(); x += 100) {
        for (int y = 0; y < height(); y += 100) {
            painter.save();
            painter.translate(x, y);
//! [10] //! [11]
            if (transformed) {
                painter.translate(50, 50);
                painter.rotate(60.0);
                painter.scale(0.6, 0.9);
                painter.translate(-50, -50);
            }
//! [11]

//! [12]
            switch (shape) {
            case Line:
                painter.drawLine(rect.bottomLeft(), rect.topRight());
                break;
            case Points:
                painter.drawPoints(points, 4);
                break;
            case Polyline:
                painter.drawPolyline(points, 4);
                break;
            case Polygon:
                painter.drawPolygon(points, 4);
                break;
            case Rect:
                painter.drawRect(rect);
                break;
            case RoundedRect:
                painter.drawRoundedRect(rect, 25, 25, Qt::RelativeSize);
                break;
            case Ellipse:
                painter.drawEllipse(rect);
                break;
            case Arc:
                painter.drawArc(rect, startAngle, arcLength);
                break;
            case Chord:
                painter.drawChord(rect, startAngle, arcLength);
                break;
            case Pie:
                painter.drawPie(rect, startAngle, arcLength);
                break;
            case Path:
                painter.drawPath(path);
                break;
            case Text:
                painter.drawText(rect,
                                 Qt::AlignCenter,
                                 tr("Qt by\nThe Qt Company"));
                break;
            case Pixmap:
                painter.drawPixmap(10, 10, pixmap);
            }
//! [12] //! [13]
            painter.restore();
        }
    }

    painter.setRenderHint(QPainter::Antialiasing, false);
    painter.setPen(palette().dark().color());
    painter.setBrush(Qt::NoBrush);
    painter.drawRect(QRect(0, 0, width() - 1, height() - 1));
}

绘制时间 会一直调用绘制

这里函数 也没有啥 就是根据 combox 选择不同 枚举就不同 就绘制 不同的形状

结尾:

我们看 官方的demo 就是学习 他的代码
代码,结构整体看下来 很清晰明了
还学到QCombox additem 重载里可以写QVariant 类型
tr("&") 和 setBuddy（）可学到了 快捷键直接让某个伙伴得到焦点

wildPointer_
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