如何删除QGraphicsView＆Scene

Question

我正在使用Qt Creator创建一个简单的程序。

QPushButton已插入QGraphicsView和QGraphicsScene中。 但是，插入的PushButton周围有一条灰色边界线，如下图所示。

我尝试使用StyleSheet作为“边框：无”或“轮廓：无”将其删除，但无法删除。

如果再次按下“绘制按钮”或将此对话框窗口移至双屏的另一个屏幕，则灰色边框消失。但是，当我将鼠标移到按钮上时，灰色边界线再次出现。 我需要帮助才能摆脱它。

下面是我的代码。

main.cpp

#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QGraphicsScene>

#include "drawscene.h"

namespace Ui { class MainWindow; }

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private slots:
    void on_pushButton_clicked();
    void on_pushButton_2_clicked();

private:
    Ui::MainWindow *ui;
    QGraphicsScene *mainScene;

    bool is_drawed;

    drawScene *mDrawScene;
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    mainScene = new QGraphicsScene(this);
    ui->graphicsView->setScene(mainScene);

    is_drawed = false;
    mDrawScene = new drawScene(mainScene, this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_pushButton_clicked()
{
    ui->graphicsView->setBackgroundBrush(QBrush("#e7e7e7"));

    if (!is_drawed) {
        mDrawScene->drawBttnView();
        is_drawed = true;
    }
}

void MainWindow::on_pushButton_2_clicked()
{
    ui->graphicsView->setBackgroundBrush(QBrush("white"));

    if (is_drawed) {
        mDrawScene->clearBttnView();
        is_drawed = false;
    }
}

mroundrect.h

#ifndef MROUNDRECT_H
#define MROUNDRECT_H

#include <QGraphicsItem>
#include <QPainter>
#include <QRectF>

class mRoundRect : public QGraphicsItem
{
public:
    mRoundRect();

    void setRndRectPos(QRect rect);

private:
    QRect rndRect;

protected:
    QRectF boundingRect() const;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
};

#endif // MROUNDRECT_H

mroundrect.cpp

#include "mroundrect.h"

mRoundRect::mRoundRect() { }

void mRoundRect::setRndRectPos(QRect rect) { rndRect = rect; }

QRectF mRoundRect::boundingRect() const { return QRectF(0, 0, 0, 0); }

void mRoundRect::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    Q_UNUSED(option);
    Q_UNUSED(widget);

    painter->setBrush(QBrush(Qt::white));
    painter->setPen(QPen(Qt::gray));
    painter->drawRoundedRect(rndRect, 15.0, 15.0);
}

drawscene.h

#ifndef DRAWSCENE_H
#define DRAWSCENE_H

#include <QGraphicsProxyWidget>
#include <QGraphicsScene>
#include <QGraphicsItem>
#include <QPushButton>
#include <QStringList>
#include <QRect>
#include <QList>

#include "mroundrect.h"

class drawScene
{
public:
    drawScene(QGraphicsScene *parentScene, QWidget *parent = 0);

    void drawBttnView();
    void clearBttnView();

private:
    QGraphicsScene *mScene;
    QPushButton *bttn1, *bttn2, *bttn3, *bttn4;
    mRoundRect  *rndRect;

    void setBttnItem(QPushButton *bttn, QStringList info, QRect rect);
    void freeWidget(QPushButton *bttn);
};

#endif // DRAWSCENE_H

drawscene.cpp

#include "drawscene.h"

drawScene::drawScene(QGraphicsScene *parentScene, QWidget *parent)
{
    mScene = parentScene;
    bttn1 = new QPushButton();
    bttn2 = new QPushButton();
    bttn3 = new QPushButton();
    bttn4 = new QPushButton();
    rndRect = new mRoundRect();
}

void drawScene::setBttnItem(QPushButton *bttn, QStringList info, QRect rect)
{
    QString name  = info[0],
            text  = info[1];

    QFont bttnfnt("Calibri", 12);

    bttn->setObjectName(name);
    bttn->setGeometry(rect);
    bttn->setText(text);
    bttn->setFont(bttnfnt);
    mScene->addWidget(bttn);
}

void drawScene::drawBttnView()
{
    QStringList bttnInfo;

    QRect bttnPos;

    rndRect->setRndRectPos(QRect(30, 30, 400, 300));
    mScene->addItem(rndRect);

    bttnInfo.clear();
    bttnInfo << "bttn1" << "TEST1";
    bttnPos = QRect(100, 100, 100, 30);
    setBttnItem(bttn1, bttnInfo, bttnPos);

    bttnInfo.clear();
    bttnInfo << "bttn2" << "TEST2";
    bttnPos = QRect(250, 100, 100, 30);
    setBttnItem(bttn2, bttnInfo, bttnPos);

    bttnInfo.clear();
    bttnInfo << "bttn3" << "TEST3";
    bttnPos = QRect(100, 200, 100, 30);
    setBttnItem(bttn3, bttnInfo, bttnPos);

    bttnInfo.clear();
    bttnInfo << "bttn4" << "TEST4";
    bttnPos = QRect(250, 200, 100, 30);
    setBttnItem(bttn4, bttnInfo, bttnPos);
}

void drawScene::freeWidget(QPushButton *bttn)
{
    QGraphicsProxyWidget *proxy;
    proxy = bttn->graphicsProxyWidget();
    mScene->removeItem(proxy);
    proxy->setWidget(NULL);
    //bttn->setParent(NULL);
    delete proxy;
}

void drawScene::clearBttnView()
{
    freeWidget(bttn1);
    freeWidget(bttn2);
    freeWidget(bttn3);
    freeWidget(bttn4);

    QList<QGraphicsItem *> allItems = mScene->items();
    foreach (QGraphicsItem *item, allItems) {
        mScene->removeItem(item);
        mScene->update();
    }
}

Answer 1

原因

如documentation中所述， QGraphicsView 使用QGraphicsItem::boundingRect()来确定该项目是否需要重绘。

您对boundingRect的实现返回了错误的值，从而使 QGraphicsView 愚弄了场景的哪一部分应该（重新）绘制为白色。

解决方案

在 mroundrect.cpp 中替换：

QRectF mRoundRect::boundingRect() const { return QRectF(0, 0, 0, 0); }

具有：

QRectF mRoundRect::boundingRect() const { return rndRect; }

结果