QWidget无边框无标题栏窗体 可拖动可拉伸

通常我们不想使用QMainWindow提供的标题栏，或者是QWidget的标题栏、边框，这时候我们使用了一个普通的QWidget，没有标题栏没有边框，但我们又需要有标题栏拖动的功能，边框改变大小的功能，看上去是个很矛盾的想法，所以…我们只能自己实现了。

直接贴代码吧：

CMainWindow.h

class CMainWindow : public QWidget
{
    Q_OBJECT
 
public:
    CMainWindow(QWidget *parent = 0);
    ~CMainWindow();
 
private:
    void initMainWindow();
    void initWidget();
    void assembleWidget();
 
    enum tagCursorCtrlStyle
    {
        eCursorNormal = 0,    // 普通鼠标
        eCursorHor,           // 水平拉伸
        eCursorVer,           // 垂直拉伸
        eCursorHorVer         // 水平和垂直拉伸
    };
 
    // custom title bar
    void mousePressEvent(QMouseEvent *event) Q_DECL_OVERRIDE;
    void mouseReleaseEvent(QMouseEvent *event) Q_DECL_OVERRIDE;
    void mouseMoveEvent(QMouseEvent *event) Q_DECL_OVERRIDE;
    int setCursorStyle(const QPoint& curPoint);    // 当前位置设置鼠标样式
 
    QPoint m_MousePressPos;    // 鼠标点击位置
    QPoint m_MouseMovePos;     // 鼠标移动位置
    bool   m_bMousePressed;    // 鼠标是否按下
    int    m_nMouseResize;     // 鼠标设置大小
    bool   m_bMouseResizePressed;  // 设置大小的按下
    QPoint m_ResizePressPos;   // 设置大小鼠标按下的点
 
    // title
    QWidget*         m_pTitleWidget;    // 标题栏
};


CMainWindow.cpp

#include "MainWindow.h"
 
CMainWindow::CMainWindow(QWidget *parent)
    : QWidget(parent)
    , m_bMousePressed(false)
    , m_nMouseResize(eCursorNormal)
    , m_bMouseResizePressed(false)
    , m_pTitleWidget(NULL)
{
    initMainWindow();
    initWidget();
    assembleWidget();
}
 
CMainWindow::~CMainWindow()
{
}
 
void CMainWindow::initMainWindow()
{
    setWindowFlags(Qt::FramelessWindowHint);    // 设置窗口标志
    setMinimumSize(600, 400);    // 设置最小尺寸
    setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Preferred);    // 设置尺寸属性
    setMouseTracking(true);    // 界面拉伸需要这个属性
}
 
void CMainWindow::initWidget()
{
    m_pTitleWidget = new QWidget(this);
}
 
void CMainWindow::assembleWidget()
{
    m_pTitleWidget->setFixedHeight(40);
    m_pTitleWidget->setMinimumWidth(600);
 
    m_pTitleWidget->move(0, 0);
}
 
void CMainWindow::mousePressEvent(QMouseEvent *event)
{
    if( event->button() == Qt::LeftButton &&
        m_pTitleWidget->rect().contains(event->globalPos() - this->frameGeometry().topLeft()))
    {
        m_MousePressPos = event->globalPos();
        m_bMousePressed = true;
    }
 
    if (eCursorNormal != m_nMouseResize)
    {
        m_bMouseResizePressed = true;
        m_ResizePressPos = event->pos();
    }
    event->ignore();    //表示继续向下传递事件，其他的控件还可以去获取
}
 
void CMainWindow::mouseReleaseEvent(QMouseEvent *event)
{
    if( event->button() == Qt::LeftButton )
    {
        m_bMousePressed = false;
        m_bMouseResizePressed = false;
        m_ResizePressPos.setX(0);
        m_ResizePressPos.setY(0);
        m_nMouseResize = setCursorStyle(event->pos());
    }
    event->ignore();
}
 
void CMainWindow::mouseMoveEvent(QMouseEvent *event)
{
    if( m_bMousePressed )
    {
        m_MouseMovePos = event->globalPos();
        this->move( this->pos() + m_MouseMovePos - m_MousePressPos );
        m_MousePressPos = m_MouseMovePos;
        return;
    }
 
    QPoint curPoint = event->pos();
 
    if (!m_bMouseResizePressed)
    {
        m_nMouseResize = setCursorStyle(curPoint);
    }
 
    if (m_bMouseResizePressed && !m_ResizePressPos.isNull())
    {
        switch (m_nMouseResize)
        {
        case eCursorHor:
            this->resize(curPoint.x(), this->height());
            break;
        case eCursorVer:
            this->resize(this->width(), curPoint.y());
            break;
        case eCursorHorVer:
            this->resize(curPoint.x(), curPoint.y());
            break;
        default:
            break;
        }
    }
 
    event->ignore();
}
 
int CMainWindow::setCursorStyle(const QPoint& curPoint)
{
    int nCurWidth = this->width();
    int nCurHeight = this->height();
    int nRes = eCursorNormal;
 
    if ( (nCurWidth - curPoint.x() <= 3) && (nCurHeight - curPoint.y() <= 3) )
    {
        setCursor(Qt::SizeFDiagCursor);
        nRes = eCursorHorVer;
    }
    else if (nCurWidth - curPoint.x() <= 3)
    {
        setCursor(Qt::SizeHorCursor);
        nRes = eCursorHor;
    }
    else if (nCurHeight - curPoint.y() <= 3)
    {
        setCursor(Qt::SizeVerCursor);
        nRes = eCursorVer;
    } 
    else
    {
        setCursor(Qt::ArrowCursor);
        nRes = eCursorNormal;
    }
 
    return nRes;
}

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作者：永远的魔术1号
来源：CSDN
原文：https://blog.csdn.net/zhango5/article/details/52729866
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