Qt无边框窗口实现拖动和改变大小(Qt::FramelessWindowHint)

相关资料：

https://blog.csdn.net/dragoo1/article/details/121163236    原文

代码实例：

.pro

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

CONFIG += c++11

# The following define makes your compiler emit warnings if you use
# any Qt feature that has been marked deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \
    main.cpp \
    mainwindow.cpp

HEADERS += \
    mainwindow.h

FORMS += \
    mainwindow.ui

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

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 <QtGui>


#define EDGE_MARGIN 8

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
protected:
    virtual void mouseMoveEvent(QMouseEvent * event);
    virtual void mousePressEvent(QMouseEvent * event);
    virtual void mouseReleaseEvent(QMouseEvent * event);
    virtual void enterEvent(QEvent * event);
    virtual void leaveEvent(QEvent * event);
private:
    QPoint dragPosition;   //鼠标拖动的位置
    enum {nodir,
        top = 0x01,
        bottom = 0x02,
        left = 0x04,
        right = 0x08,
        topLeft = 0x01 | 0x04,
        topRight = 0x01 | 0x08,
        bottomLeft = 0x02 | 0x04,
        bottomRight = 0x02 | 0x08
    } resizeDir; //更改尺寸的方向

private:
    void testEdge(QMouseEvent *event);  //检测鼠标是否接近窗口边缘


private:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

mainwindow.cpp

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


#define min(a,b) ((a)<(b)? (a) :(b))
#define max(a,b) ((a)>(b)? (a) :(b))


MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    resizeDir = nodir;   //初始化检测方向为无
    setWindowFlags(Qt::FramelessWindowHint);  //设置无边框
    setMouseTracking(true); //开启鼠标追踪
    setMinimumSize(90, 200);
}

void MainWindow::mousePressEvent(QMouseEvent * event)
{
    if (event->button() == Qt::LeftButton)  //每当按下鼠标左键就记录一下位置
    {
        dragPosition = event->globalPos() - frameGeometry().topLeft();  //获得鼠标按键位置相对窗口左上面的位置
    }
}

void MainWindow::testEdge(QMouseEvent *event)
{
    int diffLeft = event->globalPos().x() - frameGeometry().left();      //计算鼠标距离窗口上下左右有多少距离
    int diffRight = event->globalPos().x() - frameGeometry().right();
    int diffTop = event->globalPos().y() - frameGeometry().top();
    int diffBottom = event->globalPos().y() - frameGeometry().bottom();

    Qt::CursorShape cursorShape;

    if(diffTop < EDGE_MARGIN && diffTop>=0){                              //根据 边缘距离 分类改变尺寸的方向
        if(diffLeft < EDGE_MARGIN && diffLeft>=0){
            resizeDir = topLeft;
            cursorShape = Qt::SizeFDiagCursor;
        }
        else if(diffRight > -EDGE_MARGIN && diffRight<=0){
            resizeDir = topRight;
            cursorShape = Qt::SizeBDiagCursor;
        }
        else{
            resizeDir = top;
            cursorShape = Qt::SizeVerCursor;
        }
    }
    else if(abs(diffBottom) < EDGE_MARGIN && diffBottom<=0){
        if(diffLeft < EDGE_MARGIN && diffLeft>=0){
            resizeDir = bottomLeft;
            cursorShape = Qt::SizeBDiagCursor;
        }
        else if(diffRight > -EDGE_MARGIN && diffRight<=0){
            resizeDir = bottomRight;
            cursorShape = Qt::SizeFDiagCursor;
        }
        else{
            resizeDir = bottom;
            cursorShape = Qt::SizeVerCursor;
        }
    }
    else if(abs(diffLeft) < EDGE_MARGIN){
        resizeDir = left;
        cursorShape = Qt::SizeHorCursor;
    }
    else if(abs(diffRight) < EDGE_MARGIN){
        resizeDir = right;
        cursorShape = Qt::SizeHorCursor;
    }
    else{
        resizeDir = nodir;
        cursorShape = Qt::ArrowCursor;
    }

    QApplication::setOverrideCursor(cursorShape);
}

void MainWindow::mouseMoveEvent(QMouseEvent * event)
{
    if (event->buttons() & Qt::LeftButton){                 //如果左键是按下的
        if(resizeDir == nodir){                             //如果鼠标不是放在边缘那么说明这是在拖动窗口
            move(event->globalPos() - dragPosition);
        }
        else{
            int ptop,pbottom,pleft,pright;                   //窗口上下左右的值
            ptop = frameGeometry().top();
            pbottom = frameGeometry().bottom();
            pleft = frameGeometry().left();
            pright = frameGeometry().right();
            if(resizeDir & top){                               //检测更改尺寸方向中包含的上下左右分量
                if(height() == minimumHeight()){
                    ptop = min(event->globalY(),ptop);
                }
                else if(height() == maximumHeight()){
                    ptop = max(event->globalY(),ptop);
                }
                else{
                    ptop = event->globalY();
                }
            }
            else if(resizeDir & bottom){
                if(height() == minimumHeight()){
                    pbottom = max(event->globalY(),ptop);
                }
                else if(height() == maximumHeight()){
                    pbottom = min(event->globalY(),ptop);
                }
                else{
                    pbottom = event->globalY();
                }
            }

            if(resizeDir & left){                        //检测左右分量
                if(width() == minimumWidth()){
                    pleft = min(event->globalX(),pleft);
                }
                else if(width() == maximumWidth()){
                    pleft = max(event->globalX(),pleft);
                }
                else{
                    pleft = event->globalX();
                }
            }
            else if(resizeDir & right){
                if(width() == minimumWidth()){
                    pright = max(event->globalX(),pright);
                }
                else if(width() == maximumWidth()){
                    pright = min(event->globalX(),pright);
                }
                else{
                    pright = event->globalX();
                }
            }
            setGeometry(QRect(QPoint(pleft,ptop),QPoint(pright,pbottom)));
        }
    }
    else testEdge(event);   //当不拖动窗口、不改变窗口大小尺寸的时候  检测鼠标边缘
}
void MainWindow::mouseReleaseEvent(QMouseEvent *event)
{
    if(resizeDir != nodir){         //还原鼠标样式
        testEdge(event);
    }
}

void MainWindow::enterEvent(QEvent * event)
{
    QWidget::enterEvent(event);
}

void MainWindow::leaveEvent(QEvent * event)
{
    QApplication::setOverrideCursor(Qt::IBeamCursor);
    QWidget::leaveEvent(event);
}

mainwindow.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>600</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget"/>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>800</width>
     <height>22</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <resources/>
 <connections/>
</ui>

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