通过label来显示各种事件
鼠标按下事件

//按下显示坐标
void MyLabel::mousePressEvent(QMouseEvent * ev)
{
	int i = ev->x();
	int j = ev->y();

	//判断按下的鼠标键位
	if (ev->button() == Qt::LeftButton) {
		qDebug() << "LeftButton";
	}
	else if (ev->button() == Qt::RightButton) {
		qDebug() << "RightButton";
	}
	else if (ev->button() == Qt::MidButton)
	{
		qDebug() << "MidButton";
	}

	QString text = QString("<center><h1>Mouse Press:(%1,%2)</center></h1>").arg(i).arg(j);
	this->setText(text);
}

鼠标抬起事件

//鼠标抬起
void MyLabel::mouseReleaseEvent(QMouseEvent* ev)
{
	QString text = QString("<center><h1>Mouse Release:(%1,%2)</center></h1>").arg(ev->x()).arg(ev->y());
	this->setText(text);
}

鼠标移动事件

//鼠标移动，不设置this->setMouseTracking(true);需要按下后移动才有效
void MyLabel::mouseMoveEvent(QMouseEvent* ev)
{
	QString text = QString("<center><h1>Mouse Move:(%1,%2)</center></h1>").arg(ev->x()).arg(ev->y());
	this->setText(text);
}

#include "MyLabel.h"
#include <QMouseEvent>
#include <QDebug>

MyLabel::MyLabel(QWidget *parent)
	: QLabel(parent)
{
	//设置默认追踪鼠标，就可以不先点击就触发移动事件
	this->setMouseTracking(true);
}

MyLabel::~MyLabel()
{}

//按下显示坐标
void MyLabel::mousePressEvent(QMouseEvent * ev)
{
	int i = ev->x();
	int j = ev->y();

	//判断按下的鼠标键位
	if (ev->button() == Qt::LeftButton) {
		qDebug() << "LeftButton";
	}
	else if (ev->button() == Qt::RightButton) {
		qDebug() << "RightButton";
	}
	else if (ev->button() == Qt::MidButton)
	{
		qDebug() << "MidButton";
	}

	QString text = QString("<center><h1>Mouse Press:(%1,%2)</center></h1>").arg(i).arg(j);
	this->setText(text);
}

//鼠标抬起
void MyLabel::mouseReleaseEvent(QMouseEvent* ev)
{
	QString text = QString("<center><h1>Mouse Release:(%1,%2)</center></h1>").arg(ev->x()).arg(ev->y());
	this->setText(text);
}

//鼠标移动，不设置this->setMouseTracking(true);需要按下后移动才有效
void MyLabel::mouseMoveEvent(QMouseEvent* ev)
{
	QString text = QString("<center><h1>Mouse Move:(%1,%2)</center></h1>").arg(ev->x()).arg(ev->y());
	this->setText(text);
}