Question

我正在尝试一些看起来很容易的东西，但我正在努力解决它。我希望能够在GUI中绘制矩形。我现在在做的是：

我使用Qt Designer创建了一个GUI，其中包含了一个QGraphicsView。
在我的主窗口中，我创建了一个myGraphicsScene（从QGraphicsScene派生的类，但是通过鼠标按下，移动和释放事件被覆盖），我将场景设置为在UI中创建的QGraphicsView。
问题是我在更改场景时无法正确控制视图的刷新和更新。

以下是代码的相关部分：

MainGUIWindow构造函数和初始化：

MainGUIWindow::MainGUIWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainGUIWindow)
{

    ui->setupUi(this);
    _init();
}

void MainGUIWindow::_init()
{

    scene = new myGraphicsScene(ui->frame_drawing);
    scene->setSceneRect(QRectF(QPointF(-100, 100), QSizeF(200, 200)));

    ui->graphicsView->setScene(scene);
    QRect rect(10, 20, 80, 60);
    scene->addText("Hello world!");
    scene->addRect(rect, QPen(Qt::black), QBrush(Qt::blue));
}

我可以很好地看到HelloWorld文本和这个矩形。但是，当我开始点击事件时，我不再正确地获得更新。

myGraphicsScene类标题：

#ifndef MYGRAPHICSSCENE_H
#define MYGRAPHICSSCENE_H

#include <QGraphicsScene>

class QGraphicsSceneMouseEvent;
class QPointF;
class QColor;

class myGraphicsScene : public QGraphicsScene
{
    Q_OBJECT

public:
    explicit myGraphicsScene(QObject *parent = 0);

public slots:

signals:

protected:
    void mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent) override;
    void mouseMoveEvent(QGraphicsSceneMouseEvent *mouseEvent) override;
    void mouseReleaseEvent(QGraphicsSceneMouseEvent *mouseEvent) override;

private:
    QPen* pen;
    QBrush* brush;
    QRect* rect;
    QPoint* p1;
    QPoint* p2;

    bool firstClick;

    // bool startedRect;
};

#endif

myGraphicsScene类实现：

#include "myGraphicsScene.h"

#include <QGraphicsSceneMouseEvent>
#include <QRect>

myGraphicsScene::myGraphicsScene(QObject *parent)
    : QGraphicsScene(parent)
{
    pen = new QPen(Qt::black);
    brush = new QBrush(Qt::blue);
    rect = 0;
    // startedRect = false;
    firstClick = true;
}


void myGraphicsScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
    if (mouseEvent->button() != Qt::LeftButton)
        return;


    // rect = new QRect((mouseEvent->scenePos()).toPoint(), (mouseEvent->scenePos()).toPoint());
    // addRect(*rect, *pen, *brush);
    // startedRect = true;

    if(firstClick)
    {
        p1 = new QPoint((mouseEvent->scenePos()).toPoint());
        QRect tmp_rect(*p1, *p1);
        addRect(tmp_rect, *pen, *brush);
    }
    else
    {
        p2 = new QPoint((mouseEvent->scenePos()).toPoint());
        QRect tmp_rect(*p2, *p2);
        addRect(tmp_rect, *pen, *brush);
    }
    QGraphicsScene::mousePressEvent(mouseEvent);
}

void myGraphicsScene::mouseMoveEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
    // if(startedRect)
    // {
    //     rect->moveBottomRight((mouseEvent->scenePos()).toPoint());
    //     qDebug("Mouse Position: %d, %d", (mouseEvent->scenePos()).toPoint().x(), (mouseEvent->scenePos()).toPoint().y());
    //     qDebug("Rectangle BottomRight Position: %d, %d", rect->bottomRight().x(), rect->bottomRight().y());
    // }
    QGraphicsScene::mouseMoveEvent(mouseEvent);
}

void myGraphicsScene::mouseReleaseEvent(QGraphicsSceneMouseEvent *mouseEvent)
{

    if (mouseEvent->button() != Qt::LeftButton)
        return;
    // rect = 0;
    // startedRect = false;
    if(firstClick)
    {
        firstClick = false;
    }
    else
    {
        rect = new QRect(*p1, *p2);
        addRect(*rect, *pen, *brush);
        p1 = 0;
        p2 = 0;
        rect = 0;
        firstClick = true;
    }
    QGraphicsScene::mouseReleaseEvent(mouseEvent);
}

我最初的想法是以拖放方式绘制矩形，但最终最终尝试了两次点击方法，这种方法效果更好但仍然没有完全更新视图。< / p>

我是Qt的新手，所以我不太熟悉它应该如何完成。任何帮助将不胜感激，因为我已经有一段时间在这里停留了一段时间。

谢谢！

Answer 1

在您的每个mouse*Event()重载中，请调用QGraphicsScene::update()方法。它将在视图上安排重绘。

http://doc.qt.io/qt-5/qgraphicsscene.html#update

Answer 2

我刚刚找到解决方案：我必须实际更改添加到场景中的项目，而不是矩形。所以，现在，我的代码看起来像：

#include "myGraphicsScene.h"

#include <QGraphicsSceneMouseEvent>
#include <QRect>
#include <QGraphicsRectItem>

myGraphicsScene::myGraphicsScene(QObject *parent)
    : QGraphicsScene(parent)
{
    pen = new QPen(Qt::black);
    brush = new QBrush(Qt::blue);

    tmp_rect = 0;
    startedRect = false;
    // firstClick = true;
}


void myGraphicsScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
    if (mouseEvent->button() != Qt::LeftButton)
        return;


    // Drag and drop approach

    startedRect = true;
    p1 = new QPointF(mouseEvent->scenePos());
    tmp_rect = new QRectF(*p1, *p1);
    // addRect(*tmp_rect, *pen, *brush);
    tmp_rect_item = new QGraphicsRectItem(*tmp_rect);
    rectangles.push_back(tmp_rect_item);
    addItem(rectangles.back());

    // Two-clicks approach
    // if(firstClick)
    // {
    //     p1 = new QPointF(mouseEvent->scenePos());
    //     tmp_rect_item = addRect(QRect(p1->toPoint(), p1->toPoint()), *pen, *brush); //save it to remove it after
    // }
    // else
    // {
    //     p2 = new QPointF(mouseEvent->scenePos());
    //     // QRect tmp_rect(*p2, *p2);
    //     // addRect(tmp_rect, *pen, *brush);
    // }


    update();
    QGraphicsScene::mousePressEvent(mouseEvent);
}

void myGraphicsScene::mouseMoveEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
    if(startedRect)
    {
        tmp_rect_item->setRect(QRectF(*p1, mouseEvent->scenePos()));
        qDebug("Mouse Position: %d, %d", (mouseEvent->scenePos()).toPoint().x(), (mouseEvent->scenePos()).toPoint().y());
        qDebug("Rectangle BottomRight Position: %d, %d", tmp_rect->bottomRight().x(), tmp_rect->bottomRight().y());
        update();
    }
    QGraphicsScene::mouseMoveEvent(mouseEvent);
}

void myGraphicsScene::mouseReleaseEvent(QGraphicsSceneMouseEvent *mouseEvent)
{

    if (mouseEvent->button() != Qt::LeftButton)
        return;

    // Drag and drop approach:

    tmp_rect = 0;
    startedRect = false;


    // Two-clicks approach

    // if(firstClick)
    // {
    //     firstClick = false;
    // }
    // else
    // {
    //     removeItem(tmp_rect_item);
    //     tmp_rect_item = new QGraphicsRectItem(QRectF(*p1, *p2));
    //     //            *tmp_rect, *pen, *brush);
    //     rectangles.push_back(tmp_rect_item);

    //     addItem(rectangles.back());
    //     p1 = 0;
    //     p2 = 0;
    //     tmp_rect = 0;
    //     firstClick = true;
    // }

    update();
    QGraphicsScene::mouseReleaseEvent(mouseEvent);
}

Answer 3

我发现另一个有用的提示是，当我扩展视图时，我将鼠标事件处理程序置于＆＃34; public＆＃34;而不是＆＃34;受保护＆＃34;。我做了改变，呼叫是一致的。

Qt - QGraphicsScene和QGraphicsView没有更新更改？

3 个答案: