QQuickPaintedItem鼠标精准拾取（pick/select）研究

QT C++在2D图形方面已经做的很完善了，在PC端（Windows、Linux和MaC）上都有很好的表现。

QT中的QML特别适合于移动端应用的开发，QML中的一些基本形状类型并不是一一地与Qt C++相对应，但是通过C++可以来扩展QML。

QQuickPaintedItem继承自QQuickItem，提供了使用QPainter API的方法来扩展QML中的2D图形项。

QQuickPaintedItem没有像QGraphicsItem那样提供shape()方法来获取图形项的具体实际形状，但是其包含contains()方法，我们可以间接地结合鼠标操作点来判断是否包含在实际形状范围内。

废话不多说，直接上测试代码：

CustomItem.h
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#ifndef CUSTOMITEM_H
#define CUSTOMITEM_H

#include <QQuickPaintedItem>
#include <QQuickItem>
#include <QMouseEvent>
#include <QPainter>

class CustomItem : public QQuickPaintedItem
{
    Q_OBJECT
    Q_PROPERTY(QString name READ name WRITE setName)
    Q_PROPERTY(QColor color READ color WRITE setColor)

public:
    CustomItem(QQuickItem *parent = nullptr);

    QString name() const;
    void setName(const QString &name);

    QColor color() const;
    void setColor(const QColor &color);

    // override paint() for actual painting.
    virtual void paint(QPainter *painter);
    // override contans() for shape mask, Q_INVOKABLE for QML use.
    Q_INVOKABLE virtual bool contains(const QPointF &point) const;

    virtual void mousePressEvent(QMouseEvent *event);
    virtual void mouseMoveEvent(QMouseEvent *event);
    virtual void mouseReleaseEvent(QMouseEvent *event);

private:
    QString m_name;
    QColor m_color;
};

#endif // CUSTOMITEM_H
 CustomItem.cpp
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#include "CustomItem.h"
#include <QPainter>
#include <QPainterPathStroker>
#include <QDebug>

CustomItem::CustomItem(QQuickItem *parent)
    : QQuickPaintedItem(parent)
{
    setAcceptedMouseButtons(Qt::LeftButton
                            | Qt::RightButton
                            | Qt::MiddleButton);
    setFlag(QQuickItem::ItemHasContents);
}

QString CustomItem::name() const
{
    return m_name;
}

void CustomItem::setName(const QString &name)
{
    m_name = name;
}

QColor CustomItem::color() const
{
    return m_color;
}

void CustomItem::setColor(const QColor &color)
{
    m_color = color;
}

void CustomItem::paint(QPainter *painter)
{
    // pen & brush
    QPen pen(m_color, 10);
    QLinearGradient gradient;
    gradient.setStart(0, 50);
    gradient.setFinalStop(200, 50);
    gradient.setColorAt(0, Qt::blue);
    gradient.setColorAt(0.2, Qt::green);
    gradient.setColorAt(0.4, Qt::red);
    gradient.setColorAt(0.6, Qt::yellow);
    gradient.setColorAt(1, Qt::cyan);
    painter->setPen(pen);
    painter->setBrush(gradient);
    painter->setRenderHints(QPainter::Antialiasing, true);

    // Unclosed shape
    static const QPointF points[3] =
    {
        QPointF(10.0, 100.0),
        QPointF(20.0, 10.0),
        QPointF(200.0, 50.0),
    };

    painter->save();
    pen.setJoinStyle(Qt::MiterJoin);    // MiterJoin, BevelJoin, RoundJoin
    pen.setCapStyle(Qt::RoundCap);      // FlatCap, SquareCap, RoundCap
    pen.setStyle(Qt::DashLine);
    painter->drawPolyline(points, 3);
    painter->restore();

    // Closed shape
    QPainterPath path;
    path.addEllipse(QRectF(10.0, 10.0, width() - 10.0, height() - 10.0));
    painter->drawPath(path);

    /* 三角形
    QPainterPath path;
    path.moveTo(width() / 2, 0);
    path.lineTo(width(), height());
    path.lineTo(0, height());
    path.lineTo(width() / 2, 0);
    painter->fillPath(path, m_color);
    */
}

bool CustomItem::contains(const QPointF &point) const
{
    // Unclosed shape
    static const QPointF points[3] =
    {
        QPointF(10.0, 100.0),
        QPointF(20.0, 10.0),
        QPointF(200.0, 50.0),
    };
    QPainterPath path;
    path.moveTo(points[0]);
    path.lineTo(points[1]);
    path.lineTo(points[2]);
    QPainterPathStroker stroker;
    stroker.setWidth(10);
    stroker.setJoinStyle(Qt::MiterJoin);
    stroker.setCapStyle(Qt::RoundCap);
    stroker.setDashPattern(Qt::SolidLine);
    return stroker.createStroke(path).contains(point);

    // Close shape
    QPainterPath path;
    path.addEllipse(QRectF(10.0, 10.0, width() - 10.0, height() - 10.0));
    QPainterPathStroker stroker;
    stroker.setWidth(10);
    return path.contains(point) || stroker.createStroke(path).contains(point);

    /* 三角形
    QPainterPath path;
    path.moveTo(width() / 2, 0);
    path.lineTo(width(), height());
    path.lineTo(0, height());
    path.lineTo(width() / 2, 0);
    QPainterPathStroker stroker;
    stroker.setWidth(10);
    return return path.contains(point) || stroker.createStroke(path).contains(point);
    */
}

void CustomItem::mousePressEvent(QMouseEvent *event)
{
    qDebug() << "CustomItem::mousePressEvent";
    QQuickPaintedItem::mousePressEvent(event);
}

void CustomItem::mouseMoveEvent(QMouseEvent *event)
{
    qDebug() << "CustomItem::mouseMoveEvent";
    QQuickPaintedItem::mouseMoveEvent(event);
}

void CustomItem::mouseReleaseEvent(QMouseEvent *event)
{
    qDebug() << "CustomItem::mouseReleaseEvent";
    QQuickPaintedItem::mouseReleaseEvent(event);
}

在main.cpp中注册CustomItem类型：qmlRegisterType<CustomItem>("CustomItem", 1, 0, "CustomItem");

 

 

 main.cpp
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#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include "CustomItem.h"

int main(int argc, char *argv[])
{
    qputenv("QT_IM_MODULE", QByteArray("qtvirtualkeyboard"));

    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);

    QGuiApplication app(argc, argv);

    qmlRegisterType<CustomItem>("CustomItem", 1, 0, "CustomItem");

    QQmlApplicationEngine engine;
    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                     &app, [url](QObject * obj, const QUrl & objUrl)
    {
        if (!obj && url == objUrl)
            QCoreApplication::exit(-1);
    }, Qt::QueuedConnection);
    engine.load(url);

    return app.exec();
}

在qml文件中使用：

 main.qml
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import QtQuick 2.12
import QtQuick.Window 2.12
import QtQuick.Controls 2.5
import CustomItem 1.0


Window {
    id: window
    visible: true
    width: 640
    height: 480
    title: qsTr("qml-2d-viewer")

    Button {
        id: btn
        anchors.right: parent.right
        anchors.bottom: parent.bottom
        text: "Populate"
        onClicked: {
            var object = Qt.createQmlObject(
                        'import QtQuick 2.12;
                         import CustomItem 1.0;
                         CustomItem {
                            width: 100
                            height: 50
                            x: window.width * Math.random()
                            y: window.height * Math.random()
                            name: "A simple Rectangle Item"
                            color: Qt.rgba(Math.random(), Math.random(), Math.random(), 1)

                            MouseArea {
                                anchors.fill: parent
                                onPressed: {
                                    if (parent.contains(Qt.point(mouse.x, mouse.y))){
                                        drag.target = parent
                                        parent.color = Qt.rgba(Math.random(), Math.random(), Math.random(), 1);
                                        parent.update();
                                    }
                                    else{
                                        drag.target = null
                                    }
                                }
                                drag.axis: Drag.XAndYAxis
                                drag.minimumX: 0
                                drag.maximumX: window.width - parent.width
                                drag.minimumY: 0
                                drag.maximumY: window.height - parent.width
                                }
                            }',
                        parent,
                        "dynamicSnippet");
        }
    }

    // QML Rectangle Type
    Rectangle {
        id: blueSquare
        width: 120; height: 120
        x: window.width - width - 10; y: 10    // making this item draggable, so don't use anchors
        color: "blue"
        visible: false

        Text { text: "Drag"; font.pixelSize: 16; color: "white"; anchors.centerIn: parent }

        MouseArea {
            anchors.fill: parent
            //! [drag]
            drag.target: blueSquare
            drag.axis: Drag.XAndYAxis
            drag.minimumX: 0
            drag.maximumX: window.width - parent.width
            drag.minimumY: 0
            drag.maximumY: window.height - parent.width
            //! [drag]
        }
    }

    // CustomItem Type Inherited from QQuickPaintedItem
    CustomItem {
        id: aRectangle
        width: 200
        height: 100
        name: "A simple Rectangle Item"
        color: "red"

        MouseArea {
            anchors.fill: parent
            onPressed: {
                if (parent.contains(Qt.point(mouse.x, mouse.y))){
                    drag.target = parent
                    parent.color = Qt.rgba(Math.random(), Math.random(), Math.random(), 1);
                    parent.update();
                }
                else{
                    drag.target = null
                }
            }
            drag.axis: Drag.XAndYAxis
            drag.minimumX: 0
            drag.maximumX: window.width - parent.width
            drag.minimumY: 0
            drag.maximumY: window.height - parent.width
        }
    }
}

Q_INVOKABLE宏将contains()方法注册到元对象系统中，这样QML就可以调用该方法来判断鼠标指针点是否在图形项形状区域，从而实现精准拾取。

在QML中MouseArea为简单的鼠标交互提供了方便，比较容易使用，如果有了MouseArea，则C++中的鼠标响应事件就不再响应。

posted on 2019-07-24 15:40  我来乔23  阅读(2315)  评论(0)  编辑  收藏  举报

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