事件 mousePressEvent、paintEvent、closeEvent、keyPressEvent

鼠标样式的设置

按WSAD通过keyPressEvent事件移动按钮

通过事件mousePressEvent获取鼠标位置的相对位置，绝对位置

cusor 鼠标样式设置成十字星

.h

#ifndef DEFAULTHANDLEREXAMPLE_H
#define DEFAULTHANDLEREXAMPLE_H

#include <QWidget>
#include <QPaintEvent>

namespace Ui {
class DefaultHandlerExample;
}

class DefaultHandlerExample : public QWidget
{
    Q_OBJECT
protected:
    void paintEvent(QPaintEvent *event);
    void closeEvent(QCloseEvent *event);
    void keyPressEvent(QKeyEvent *event);
    void showEvent(QShowEvent *event);
    void hideEvent(QHideEvent *event);
    void mousePressEvent(QMouseEvent *event);

public:
    explicit DefaultHandlerExample(QWidget *parent = nullptr);
    ~DefaultHandlerExample();

private:
    Ui::DefaultHandlerExample *ui;
};

#endif // DEFAULTHANDLEREXAMPLE_H

.cpp

#include "defaulthandlerexample.h"
#include "ui_defaulthandlerexample.h"

#include <QMessageBox>
#include <QPainter>

DefaultHandlerExample::DefaultHandlerExample(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::DefaultHandlerExample)
{
    ui->setupUi(this);
    this->setMouseTracking(false);//只有按下鼠标才会跟踪
}

DefaultHandlerExample::~DefaultHandlerExample()
{
    delete ui;
}
void DefaultHandlerExample::paintEvent(QPaintEvent *event)
{
    Q_UNUSED(event);
    QPainter painter(this);
    painter.drawPixmap(0,0,this->width(),this->height(),
                       QPixmap(":/toolbar/images/background.jpg"));
}

void DefaultHandlerExample::closeEvent(QCloseEvent *event)
{
    QString dlgTitle ="提示";
    QString strInfo ="确定要退出吗?";
    QMessageBox::StandardButton result=
        QMessageBox::question(this,dlgTitle,strInfo,QMessageBox::Yes|QMessageBox::No|QMessageBox::Cancel);
    if(result== QMessageBox::Yes)
        event->accept();//窗口确认关闭
    else
        event->ignore();//忽略
}

void DefaultHandlerExample::keyPressEvent(QKeyEvent *event)
{
    QPoint pt = ui->btnMove->pos();
    if((event->key()== Qt::Key_A)|| (event->key()==Qt::Key_Left))
        ui->btnMove->move(pt.x()-20,pt.y());
    if((event->key()== Qt::Key_D)|| (event->key()==Qt::Key_Right))
        ui->btnMove->move(pt.x()+20,pt.y());
    if((event->key()== Qt::Key_W)|| (event->key()==Qt::Key_Up))
        ui->btnMove->move(pt.x(),pt.y()-20);

    if((event->key()== Qt::Key_S)|| (event->key()==Qt::Key_Down))
        ui->btnMove->move(pt.x(),pt.y()+20);

    // this->setWindowTitle(event->ke);
}

void DefaultHandlerExample::showEvent(QShowEvent *event)
{
    Q_UNUSED(event);
    ui->label->setText("showEvent函数被触发");
}

void DefaultHandlerExample::hideEvent(QHideEvent *event)
{
    Q_UNUSED(event);
    ui->label->setText("hideEvent函数被触发");
}

void DefaultHandlerExample::mousePressEvent(QMouseEvent *event)
{
    if(event->button()==Qt::LeftButton)
    {
        QPoint pt = event->pos(); //窗口上的相对坐标
        QPointF relaPt = event->position(); //相对坐标
        QPointF winPt = event->scenePosition();//相对坐标
        QPointF globalPt = event->globalPosition();//屏幕上的绝对坐标
        QString str = QString::asprintf("pos()=(%d,%d)",pt.x(),pt.y());
        str+= QString::asprintf("\nposition()=%.0f,%.0f",relaPt.x(),relaPt.y());
        str+= QString::asprintf("\nscenePosition()=%.0f,%.0f",winPt.x(),winPt.y());
        str+= QString::asprintf("\nglobalPosition()=%.0f,%.0f",globalPt.x(),globalPt.y());

        ui->label->setText(str);
        ui->label->adjustSize();
        ui->label->move(event->pos());//标签移动到鼠标光标处
    }

    QWidget::mousePressEvent(event);
}

效果