c++ - 在 QLayout 中创建和删除自定义 QWidgets 时出现 RAM 问题

Question

我创建了一个自定义的QWidget(下面的代码)[里面有一个QHBoxLayout和两个QPushButtons]并将它添加到一个QVBoxLayout 在 GUI 中。这个自定义 QWidget 对象将被创建和删除几次(下面的代码)。

当我在控制台(在嵌入式 Linux 上)中键入 top 时，每次添加新的 QWidget 时，RAM 都会增加。没关系!但是我看不到删除时 RAM 的减少。

我的代码有什么问题？我希望 RAM 在删除自定义 QWidgets 时减少。

我的自定义控件.h

class QCustomPushButton_withinIcon_LeftAndRight : public QWidget {
    Q_OBJECT

public:
    //functions
    QCustomPushButton_withinIcon_LeftAndRight(QWidget *parent = 0);
    ~QCustomPushButton_withinIcon_LeftAndRight();

    //other slots like:
    // - virtual void mousePressEvent();
    // - virtual void mouseReleaseEvent();
    //other signals like:
    // - void clicked();
    //other functions like:
    // - virtual void setEnabled(bool a);
    // - virtual void paintEvent(QPaintEvent *);
    // - ...

private:
    //variables
    QLayout *innerLayout;           //!< Layout for two buttons
    QPushButton *buttonLeft;        //!< Button left
    QPushButton *buttonRight;       //!< Button right

    //other variables like:
    // - bool enabled;
    // - ...
};

我的自定义控件.cpp

QCustomPushButton_withinIcon_LeftAndRight::QCustomPushButton_withinIcon_LeftAndRight(QWidget *parent) :
    QWidget(parent),
    mSVG (new svg),
    mGradient (new gradient)
{
    enabled = true;

    //create innerLayout
    innerLayout = new QHBoxLayout();
    this->setLayout(innerLayout);

    //create buttons
    buttonLeft = new QPushButton();
    buttonRight = new QPushButton();
    innerLayout->addWidget(buttonLeft);
    innerLayout->addWidget(buttonRight);

    //create connections like:
    // - connect (buttonLeft, SIGNAL(pressed()), this, SLOT(mousePressEvent()));
    // - ...

    //set some stylesheets
    // - buttonLeft->setStyleSheet("...");
}
QCustomPushButton_withinIcon_LeftAndRight::~QCustomPushButton_withinIcon_LeftAndRight()
{
    //I think, that this is right. If not, correct me.
    delete buttonLeft;
    delete buttonRight;
    delete innerLayout;
}

//void QCustomPushButton_withinIcon_LeftAndRight::mousePressEvent() {}
//void QCustomPushButton_withinIcon_LeftAndRight::mouseReleaseEvent() {}
//void QCustomPushButton_withinIcon_LeftAndRight::setEnabled(bool a) {}
//void QCustomPushButton_withinIcon_LeftAndRight::paintEvent(QPaintEvent *) {} ...

gui.cpp(将QWidgets添加到GUI中的QLayout)

    QCustomPushButton_withinIcon_LeftAndRight *button = new QCustomPushButton_withinIcon_LeftAndRight();
    //add button to layout
    parentUiWindow->aLayoutNameInGui->addWidget(button);
    //aLayoutNameInGui is type of QVBoxLayout

gui.cpp(删除GUI中QLayout中的QWidgets)

    //delete all buttons in layout
    QLayoutItem *child;
    while((child = parentUiWindow->aLayoutNameInGui->layout()->takeAt(0)) != 0) {
        //parentUiWindow->aLayoutNameInGui->removeWidget(child->widget()); //already removed by ->takeAt()
        //child->widget()->setParent(NULL);
        delete child->widget();
        delete child;
    }

Answer 1

当您使用 top 命令查看内存使用情况时，您可能会得到误报。正如一些程序员所述，当您对某些对象调用delete 时，操作系统并不总是从您的进程中释放分配的内存。

但是，您正在使用 new 在 QCustomPushButton_withinIcon_LeftAndRight 构造函数中创建两个对象:

mSVG (new svg),
mGradient (new gradient)

但你似乎从来没有破坏过这些对象。所以你可能在那里有内存泄漏。