窗口的最大化、最小化、Normal状态实现

最新推荐文章于 2023-02-01 17:45:21 发布

原创最新推荐文章于 2023-02-01 17:45:21 发布 · 2.8k 阅读

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本文介绍了一个窗口在最小化后再恢复时出现冻结的问题及其解决方案。详细分析了Qt框架中导致此现象的原因，并提供了一种通过子类化QMainWindow并手动设置Qt::WA_Mapped属性的方法来修复该问题。

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void MinimizeAppBtnClicked()
{
    showMinimized();
}

void MaximizeAppBtnClicked()
{
    maximizeBtn->hide();
    maximizeBtn->setChecked(false);
    normalBtn->show();
    normalBtn->setChecked(false);
    hide();//有些时候点击最大化按钮不起作用，所以先hide一下
    showMaximized();  
}

void NormalAppBtnClicked()
{
    maximizeBtn->show();
    maximizeBtn->setChecked(false);
    normalBtn->hide();
    normalBtn->setChecked(false);
    showNormal();
}

用上面的代码会有一个问题：

widgets freezing after minimise window(点击图标，app不刷新，设置setWindowFlags(Qt::FramelessWindowHint)引起)

原因：

What happened: Window stopped redrawing. It looked frozen.

I was debugging it and found out following:

After minimizing window attribute Qt::WA_Mapped was removed from QMainWindow (you can set breakpoint to setAttribute_internal in qwidget.cpp to check it). But this attribute was not set again after showing window. This caused that condition if (discardSyncRequest(tlw, tlwExtra)) in QWidgetBackingStore::sync was not met and it caused dirtyWidgets are not cleared. In other part of Qt updating system this caused that no other rendering was made.

Workaround I did: Subclassed QMainWindow and set attribute Qt::WA_Mapped manually when window was restored (handling changeEvent):

解决方案：

 void changeEvent(QEvent * event)
 {
     if(event->type() == QEvent::WindowStateChange)
     {
         if(!isMinimized())
         {
             setAttribute(Qt::WA_Mapped);
         }
     }
     QWidget::changeEvent(event);
 }

移动、最大化状态时拖动标题栏变成normal状态（部分代码）

void mousePressEvent(QMouseEvent *event)
{
    QPoint pointpos = event->pos();
    QRect rect(0,0,this->width(),25);
    if (rect.contains(pointpos))
    {
        QRect screenRect = QApplication::desktop()->screenGeometry();

        if (screenRect.width() != size().width())
        {
            m_bMovable = true;
            m_lastMousePos = event->globalPos();
        }
        m_bIsMousePressed = true;
    }
    else
    {
        m_bMovable = false;
    }
}

void mouseMoveEvent(QMouseEvent *event)
{
    if (!m_bIsMousePressed)
    {
        return;
    }
    QRect screenRect = QApplication::desktop()->screenGeometry();
    if (screenRect.width() == size().width())
    {
        int nRectX = event->globalPos().x() - normalGeometry().width()/2;
        if (nRectX < 0)
        {
            nRectX = 0;
        }
        if (nRectX > size().width() - normalGeometry().width())
        {
            nRectX = size().width() - normalGeometry().width();
        }
        QRect IniNormalRect(nRectX,0,normalGeometry().width(),normalGeometry().height());
        setGeometry(IniNormalRect);
        ui->maximizeBtn->show();
        ui->maximizeBtn->setChecked(false);
        ui->normalBtn->hide();
        ui->normalBtn->setChecked(false);

    }
    else if (m_bMovable)
    {  
        move(event->globalPos() - m_lastMousePos + pos());
        m_lastMousePos = event->globalPos();       
    }

}

void mouseReleaseEvent(QMouseEvent *event)
{

    m_bMovable = false;
    m_bIsMousePressed = false;
}