所以我看了here提供的涂鸦示例，我想我想在QML中实现类似的东西。考虑一下之后，我认为使用自定义qquickPaintedItem将是最好的工具。所以我想出了一个超级简约的例子：

#include "drawingcanvas.h"

#include <QPainter>

DrawingCanvas::DrawingCanvas(qquickItem *parent) : qquickPaintedItem(parent)
{
    lastPoint = QPointF(0,0);
}

void DrawingCanvas::mouseMoved(const QPointF &pos)
{
    points.append(pos); // points is a QVector<QPointF>
    currentPoint = pos;

    this->update(QRect(lastPoint.toPoint(),currentPoint.toPoint()));
}

void DrawingCanvas::paint(QPainter *painter)
{
    painter->setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform);
    painter->setPen(QPen(QColor("blue"),5,Qt::SolidLine,Qt::RoundCap,Qt::RoundJoin));
    for(int j = 1; j < points.length(); ++j){
        painter->drawLine( points.at(j - 1),points.at(j));
    }
    lastPoint = currentPoint;
}

在QML中，我写了一个简单的MouseArea和自定义类，如下所示：

import QtQuick 2.12
import QtQuick.Window 2.12
import Drawing 1.0

Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")
    DrawingCanvas {
        id: drawingCanvas
        anchors.fill: parent
    }

    MouseArea {
        anchors.fill: parent
        onPositionChanged: drawingCanvas.mouseMoved(Qt.point(mouseX,mouseY))
    }
}