QListWidget在点击并在多个项目之间拖动时导致细分错误

时间：2018-12-08 15:14:29

标签： c++ qt widget

我有一个QListWidget，其中包含多个项目，每个项目的行为都像一个单击按钮时响应的按钮。我遇到了一个问题，如果您单击一个项目并将鼠标拖到屏幕上除您单击的项目之外的任何其他位置，则该程序将导致分段错误并崩溃。有谁知道我该怎么解决？

我已经包含了下面编写的所有代码，尽管该代码还依赖于我认为无法在此处发布的专有代码

window.cc 

#include "globals.h"

#include <QLabel>
#include <QBoxLayout>
#include <QScrollArea>
#include <QListWidget>
#include <QListWidgetItem>
#include <QPushButton>
#include <QMessageBox>

#include "windowheader.h"

namespace{

class statisticsTab : public QWidget {
public:
    statisticsTab();
private:
    QGridLayout * layout;
    QLabel * title;
    QLabel * userListTitle;
    QLabel * branchListTitle;
    UserListWidget * userList;
    BranchListWidget * branchList;
    QListWidget * statsPage;
};

inline statisticsTab::statisticsTab() : QWidget() {
    layout = new QGridLayout();
    cur_repo = new GITPP::REPO();

    title = new QLabel("Repository Statistics");
    title->setStyleSheet("QLabel {font-weight: bold;}");
    layout->addWidget(title, 0, 0, 1, 2);

    userListTitle = new QLabel("Contributors");
    layout->addWidget(userListTitle, 1, 0, 1, 1);

    branchListTitle = new QLabel("Branches");
    layout->addWidget(branchListTitle, 1, 1, 1, 1);

    statsPage = new QListWidget();
    layout->addWidget(statsPage, 3, 0, 1, 2, Qt::AlignTop);
    QListWidgetItem * statsPageDefault = new QListWidgetItem(QString("Click on a contributor or branch to get started!"), 0, 0);
    statsPage->addItem(statsPageDefault);

    userList = new UserListWidget(statsPage);
    layout->addWidget(userList, 2, 0, 1, 1);

    branchList = new BranchListWidget(statsPage);
    layout->addWidget(branchList, 2, 1, 1, 1);

    if(cur_repo != nullptr) {
        GITPP::COMMITS commits = cur_repo->commits();
        std::vector <std::string> contributors;

        for(auto commit : commits) {
            contributors.push_back(commit.author());
        }

        std::sort(contributors.begin(), contributors.end());
        contributors.erase(unique(contributors.begin(), contributors.end()), contributors.end());

        for(auto contributor : contributors) {
            QString contributorName = QString::fromStdString(contributor);
            QListWidgetItem * contributorNameItem = new QListWidgetItem(contributorName);
            userList->addItem(contributorNameItem);
        }

        GITPP::BRANCHES branches = cur_repo->branches();

        for(auto branch : branches) {
            QListWidgetItem * branchName = new QListWidgetItem(QString::fromStdString(branch.name()), 0, 0);
            branchList->addItem(branchName);
        }
    } else {
        QListWidgetItem * branchListDefault = new QListWidgetItem(QString("No branches found"), 0, 0);
        branchList->addItem(branchListDefault);

        QListWidgetItem * userListDefault = new QListWidgetItem(QString("No users found"), 0, 0);
        userList->addItem(userListDefault);
    }

    setLayout(layout);
}

INSTALL_TAB(statisticsTab, "Statistics");

}

windowheader.h 

#ifndef WINDOWHEADER_H
#define WINDWOHEADER_H

#include <QListWidget>
#include <string>
#include <limits.h>
#include <unistd.h>
#include <QPushButton>
#include <QFileDialog>
#include <QMessageBox>

#include "globals.h"

class UserListWidget : public QListWidget {
    Q_OBJECT
public:
    UserListWidget(QListWidget * statsPage);

private slots:
    void updateStatsPage();
private:
    QListWidget * statsPage;
};

inline UserListWidget::UserListWidget(QListWidget * statsPageArg) : QListWidget() {
    connect(this, SIGNAL(itemSelectionChanged()), this, SLOT(updateStatsPage()));
    statsPage = statsPageArg;
}

inline void UserListWidget::updateStatsPage() {
    GITPP::CONFIG config = cur_repo->config();
    GITPP::COMMITS commits = cur_repo->commits();


    QString statsTitle = QString("Here are some stats about the user ") + this->currentItem()->text();
    QListWidgetItem * statsTitleItem = new QListWidgetItem(statsTitle);
    statsPage->clear();
    statsPage->addItem(statsTitleItem);

    for(auto thing : config) {
        QString statsInfo = QString::fromStdString(thing.name());
        QListWidgetItem * statsInfoItem = new QListWidgetItem(statsInfo);
        statsPage->addItem(statsInfoItem);
    }

    selectionModel()->clear();
}

class BranchListWidget : public QListWidget {
    Q_OBJECT
public:
    BranchListWidget(QListWidget * statsPage);

private slots:
    void updateStatsPage();
private:
    QListWidget * statsPage;
};

inline BranchListWidget::BranchListWidget(QListWidget * statsPageArg) : QListWidget() {
    connect(this, SIGNAL(itemSelectionChanged()), this, SLOT(updateStatsPage()));
    statsPage = statsPageArg;
}

inline void BranchListWidget::updateStatsPage() {
    GITPP::CONFIG config = cur_repo->config();
    GITPP::COMMITS commits = cur_repo->commits();

    QString statsTitle = QString("Here are some stats about the branch ") + this->currentItem()->text();
    QListWidgetItem * statsTitleItem = new QListWidgetItem(statsTitle);
    statsPage->clear();
    statsPage->addItem(statsTitleItem);

    for(auto thing : config) {
        QString statsInfo = QString::fromStdString(thing.name());
        QListWidgetItem * statsInfoItem = new QListWidgetItem(statsInfo);
        statsPage->addItem(statsInfoItem);
    }

    selectionModel()->clear();
}

#endif

Valgrind输出：

==9475== Invalid read of size 8
==9475==    at 0x1158B5: UserListWidget::updateStatsPage() (in /home/alexis/Desktop/programming/uni_work/comp_2811/cw2/ui_cw3/2811_gui)
==9475==    by 0x5F5D5E8: QMetaObject::activate(QObject*, int, int, void**) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.7.1)
==9475==    by 0x5F5D5E8: QMetaObject::activate(QObject*, int, int, void**) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.7.1)
==9475==    by 0x5EE0BE6: QItemSelectionModel::selectionChanged(QItemSelection const&, QItemSelection const&) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.7.1)
==9475==    by 0x5EE544A: QItemSelectionModel::emitSelectionChanged(QItemSelection const&, QItemSelection const&) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.7.1)
==9475==    by 0x5EE8F91: QItemSelectionModel::select(QItemSelection const&, QFlags<QItemSelectionModel::SelectionFlag>) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.7.1)
==9475==    by 0x54DF9B4: QListView::setSelection(QRect const&, QFlags<QItemSelectionModel::SelectionFlag>) (in /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5.7.1)
==9475==    by 0x54C6B3E: QAbstractItemView::mouseMoveEvent(QMouseEvent*) (in /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5.7.1)
==9475==    by 0x54E6386: QListView::mouseMoveEvent(QMouseEvent*) (in /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5.7.1)
==9475==    by 0x52B8277: QWidget::event(QEvent*) (in /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5.7.1)
==9475==    by 0x53A0A0D: QFrame::event(QEvent*) (in /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5.7.1)
==9475==    by 0x54C7502: QAbstractItemView::viewportEvent(QEvent*) (in /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5.7.1)
==9475==  Address 0x0 is not stack'd, malloc'd or (recently) free'd
==9475== 
==9475== 
==9475== Process terminating with default action of signal 11 (SIGSEGV)
==9475==  Access not within mapped region at address 0x0
==9475==    at 0x1158B5: UserListWidget::updateStatsPage() (in /home/alexis/Desktop/programming/uni_work/comp_2811/cw2/ui_cw3/2811_gui)
==9475==    by 0x5F5D5E8: QMetaObject::activate(QObject*, int, int, void**) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.7.1)
==9475==    by 0x5F5D5E8: QMetaObject::activate(QObject*, int, int, void**) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.7.1)
==9475==    by 0x5EE0BE6: QItemSelectionModel::selectionChanged(QItemSelection const&, QItemSelection const&) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.7.1)
==9475==    by 0x5EE544A: QItemSelectionModel::emitSelectionChanged(QItemSelection const&, QItemSelection const&) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.7.1)
==9475==    by 0x5EE8F91: QItemSelectionModel::select(QItemSelection const&, QFlags<QItemSelectionModel::SelectionFlag>) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.7.1)
==9475==    by 0x54DF9B4: QListView::setSelection(QRect const&, QFlags<QItemSelectionModel::SelectionFlag>) (in /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5.7.1)
==9475==    by 0x54C6B3E: QAbstractItemView::mouseMoveEvent(QMouseEvent*) (in /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5.7.1)
==9475==    by 0x54E6386: QListView::mouseMoveEvent(QMouseEvent*) (in /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5.7.1)
==9475==    by 0x52B8277: QWidget::event(QEvent*) (in /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5.7.1)
==9475==    by 0x53A0A0D: QFrame::event(QEvent*) (in /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5.7.1)
==9475==    by 0x54C7502: QAbstractItemView::viewportEvent(QEvent*) (in /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5.7.1)

1 个答案:

答案 0 :(得分：1)

似乎在UserListWidget::updateStatsPage()方法内发生了分段错误。

鉴于可用的信息有限，并且您说过将鼠标从最初单击的项目上移开时会发生此问题，我怀疑，this->currentItem()在其中返回空指针该方法调用this->currentItem()->text()的代码行。当您第一次单击窗口小部件列表项时，我猜测UserListWidget::updateStatsPage()方法是用从this->currentItem()返回的非空指针来调用的。但是随后您拖动鼠标，如果将其拖离当前项目，则会生成另一个itemSelectionChanged()信号。如果您完全将鼠标从QListWidget上移开，我想如果this->currentItem()返回一个空指针表示没有选择任何内容时，将调用该信号。

尝试检查this->currentItem()是否为空，并且仅在不为空时取消引用。

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