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自定义类TMyLabel ，继承自QLabel 

TMyLabel 中重新实现了 event 方法，重写了mouseDoubleClickEvent 发射信号

在主窗体中放入TMyLabel组件，将TMyLabel  mouseDoubleClickEvent 信号，  绑定到实现方法do_doubleClick()槽函数

TMyLabel.h

#ifndef TMYLABEL_H
#define TMYLABEL_H#include <QLabel>
//引用鼠标事件 鼠标双击事件mouseDoubleClickEvent才能自动带出来参数
#include <QMouseEvent>class TMyLabel : public QLabel
{Q_OBJECT
public:// TMyLabel();TMyLabel(QWidget *parent=nullptr);//重写构造函数bool event(QEvent *e);//重写event()函数
protected:void mouseDoubleClickEvent(QMouseEvent *event);//重写鼠标的双击事件
signals:void doubleClick();//自定义信号发射函数};#endif // TMYLABEL_H

TMyLabel.cpp

#include "tmylabel.h"// TMyLabel::TMyLabel(QWidget *parent): {}
TMyLabel::TMyLabel(QWidget *parent):QLabel(parent)
{this->setAttribute(Qt::WA_Hover,true);//必须设置这个属性，鼠标才能有Hover事件
}bool TMyLabel::event(QEvent *e)
{if(e->type()==QEvent::HoverEnter){//鼠标移入时，将调色板的字体颜色设置为红色QPalette palet=this->palette();palet.setColor(QPalette::WindowText,Qt::red);this->setPalette(palet);}else if(e->type()==QEvent::HoverLeave)//鼠标移出{//鼠标移出的时候 颜色再变回黑色QPalette palet = this->palette();palet.setColor(QPalette::WindowText,Qt::black);this->setPalette(palet);}return QLabel::event(e);//执行父类的的event() 执行父类要执行的事情
}void TMyLabel::mouseDoubleClickEvent(QMouseEvent *event)
{Q_UNUSED(event);emit doubleClick();//发射信号  用来父组件连接到执行槽
}

主窗体设计 

主窗体 TMyLableMouseMoveExample.h

#ifndef TMYLABLEMOUSEMOVEEXAMPLE_H
#define TMYLABLEMOUSEMOVEEXAMPLE_H#include <QWidget>
#include <QMouseEvent>namespace Ui {
class TMyLableMouseMoveExample;
}class TMyLableMouseMoveExample : public QWidget
{Q_OBJECTpublic:explicit TMyLableMouseMoveExample(QWidget *parent = nullptr);~TMyLableMouseMoveExample();protected:void mouseDoubleClickEvent(QMouseEvent *event);
private slots:void do_doubleClick();private:Ui::TMyLableMouseMoveExample *ui;
};#endif // TMYLABLEMOUSEMOVEEXAMPLE_H

主窗体TMyLableMouseMoveExample.cpp

#include "tmylablemousemoveexample.h"
#include "ui_tmylablemousemoveexample.h"TMyLableMouseMoveExample::TMyLableMouseMoveExample(QWidget *parent): QWidget(parent), ui(new Ui::TMyLableMouseMoveExample)
{ui->setupUi(this);connect(ui->lab,SIGNAL(doubleClick()),this,SLOT(do_doubleClick()));
}TMyLableMouseMoveExample::~TMyLableMouseMoveExample()
{delete ui;
}void TMyLableMouseMoveExample::mouseDoubleClickEvent(QMouseEvent *event)
{Q_UNUSED(event);ui->lab->setText("窗口被双击了");ui->lab->adjustSize();
}void TMyLableMouseMoveExample::do_doubleClick()
{ui->lab->setText("信号槽响应：TMyLabel被双击了");ui->lab->adjustSize();
}

效果