1 新建一个项目：06Event
新建cpp文件
06Event.pro
HEADERS += \
MyWidget.h
SOURCES += \
MyWidget.cpp
QT += widgets gui
MyWidget.h
#ifndef MYWIDGET_H
#define MYWIDGET_H
#include <QWidget>
#include <QPushButton>
#include <QLineEdit>
class MyWidget : public QWidget
{
Q_OBJECT
public:
explicit MyWidget(QWidget *parent = 0);
bool event(QEvent *);
void mousePressEvent(QMouseEvent *);
void mouseReleaseEvent(QMouseEvent *);
void mouseMoveEvent(QMouseEvent *);
/*不要用,因为它默认调用两次mousePressEvent*/
//void mouseDoubleClickEvent(QMouseEvent *);
void keyPressEvent(QKeyEvent *);
void keyReleaseEvent(QKeyEvent *);
void closeEvent(QCloseEvent *);
//void showEvent(QShowEvent *);
//void hideEvent(QHideEvent *);
void paintEvent(QPaintEvent *);
QPushButton* button;
QLineEdit* edit;
signals:
public slots:
void slotButtonClicked();
};
#endif // MYWIDGET_H
MyWidget.cpp
#include "MyWidget.h"
#include <QApplication>
#include <QEvent>
#include <QDebug>
#include <QMouseEvent>
#include <QKeyEvent>
#include <QVBoxLayout>
#include <QPainter>
MyWidget::MyWidget(QWidget *parent) :
QWidget(parent)
{
// QVBoxLayout* lay = new QVBoxLayout(this);
#if 0
QPushButton* button2;
lay->addWidget(button = new QPushButton("OK", this));
lay->addWidget(button2 = new QPushButton("Button2"));
//设置它为默认的焦点，当点击tab键之后可以切换焦点
button->setDefault(true);
// 鼠标不需要按下，mouseMove就能得到调用
this->setMouseTracking(true);
connect(button2, SIGNAL(clicked()), this, SLOT(slotButtonClicked()));
connect(button, SIGNAL(clicked()), this, SLOT(slotButtonClicked()));
#endif
// lay->addWidget(edit = new QLineEdit());
// connect(edit, SIGNAL(returnPressed()), this, SLOT(slotButtonClicked()));
}
//通过这一句实现点击按钮的时候获得按钮上的text()内容
void MyWidget::slotButtonClicked()
{
QLineEdit* button = (QLineEdit*)sender();
qDebug() << button->text();
}
/* QApplication先得到->具体应该处理的窗口::event()->event()根据消息类型来调用具体的虚函数 */
/* 1）可以重载具体的虚函数，来实现对消息的响应
2）可以重载event函数，用来处理或者截取消息 */
/* 截取消息 */
bool MyWidget::event(QEvent *ev)
{
// 鼠标消息被截断
// if(ev->type() == QEvent::MouseButtonPress)
// return true;
ev->accept();
return QWidget::event(ev);
}
/**
* @brief MyWidget::closeEvent 窗口关闭的事件
*/
void MyWidget::closeEvent(QCloseEvent *)
{
qDebug() << "closeEvent";
}
void MyWidget::paintEvent(QPaintEvent *)
{
QPainter p(this);
//通过下面的方式实现画线
p.drawLine(QPoint(0, 0), QPoint(100, 100));
}
/**
* @brief MyWidget::mousePressEvent 鼠标按下的事件
* @param ev
*/
void MyWidget::mousePressEvent(QMouseEvent *ev)
{
#if 0
QPoint pt = ev->pos();
qDebug() << pt;
//如果鼠标按下的是左键的处理
if(ev->button() == Qt::LeftButton){}
//如果按下的Shift键了
if(ev->modifiers() == Qt::ShiftModifier)
{
qDebug() << "shift press";
}
#endif
//改进办法：先判断是否有左键，然后如果判断是否还按了Ctrl键
if(ev->button() == Qt::LeftButton)
{
if(ev->modifiers() == Qt::ControlModifier)
{
// handle with Control;
return;
}
// handle2 without control;
} else {}
}
/**
* @brief MyWidget::mouseReleaseEvent 鼠标释放的按键
*/
void MyWidget::mouseReleaseEvent(QMouseEvent *){}
/**
* @brief MyWidget::mouseMoveEvent 鼠标移动的事件
*/
void MyWidget::mouseMoveEvent(QMouseEvent *)
{
static int i=0;
qDebug() << "mouse move"<< i++;
}
/**
* @brief MyWidget::keyPressEvent 鼠标按下的事件，通过这个可以获得按下的键
* @param ev
*/
void MyWidget::keyPressEvent(QKeyEvent *ev)
{
ev->modifiers();
int key = ev->key();
qDebug() << key;
char a = key;
qDebug() << (char)a;
}
/**
* @brief MyWidget::keyReleaseEvent 按键释放的事件
*/
void MyWidget::keyReleaseEvent(QKeyEvent *){}
int main(int argc, char* argv[])
{
QApplication app(argc, argv);
MyWidget w;
w.show();
return app.exec();
}
运行结果：
2 QT消息过滤器
EventFilter.pro
HEADERS += \
MyWidget.h \
MyApplication.h
SOURCES += \
MyWidget.cpp \
MyApplication.cpp
QT += widgets gui
MyWidget.h
#ifndef MYWIDGET_H
#define MYWIDGET_H
#include <QWidget>
#include <QPushButton>
class MyWidget : public QWidget
{
Q_OBJECT
public:
explicit MyWidget(QWidget *parent = 0);
QPushButton* _button;
bool eventFilter(QObject *, QEvent *);
bool event(QEvent *);
signals:
public slots:
};
#endif // MYWIDGET_H
MyWidget.cpp
#include "MyWidget.h"
#include <QPushButton>
#include <QEvent>
#include "MyApplication.h"
#include <QDebug>
#include <QApplication>
MyWidget::MyWidget(QWidget *parent) :
QWidget(parent)
{
QPushButton* button;
button = new QPushButton("This button", this);
connect(button, SIGNAL(clicked()), this, SLOT(close()));
_button = button;
/*button给自己安装了一个消息过滤器，那么经过button的消息，
* 都先要调用它的过滤器的eventFilter函数*/
button->installEventFilter(this);
}
bool MyWidget::eventFilter(QObject *o, QEvent *e)
{
#if 0
if(0 == (QObject*)_button &&(
e->type() == QEvent::MouseButtonRelease ||
e->type() == QEvent::MouseButtonDblClick ||
e->type() == QEvent::MouseButtonPress)) {
return true;
}
#endif
return QWidget::eventFilter(o,e);
}
bool MyWidget::event(QEvent *e)
{
if(e->type() == QEvent::User)
{
qDebug() << "User event is comming";
}
return QWidget::event(e);
}
int main(int argc,char *argv[])
{
MyApplication app(argc,argv);
MyWidget w;
w.show();
//发送一个Event给MyWidget
qDebug() << "begin send";
app.postEvent(&w,new QEvent(QEvent::User));
qDebug() << "end send";
return app.exec();
}
MyApplication.h
#ifndef MYAPPLICATION_H
#define MYAPPLICATION_H
#include <QApplication>
class MyApplication : public QApplication
{
Q_OBJECT
public:
MyApplication(int argc,char *argv[]):QApplication(argc,argv)
{}
bool notify(QObject *,QEvent *);
signals:
public slots:
};
#endif // MYAPPLICATION_H
MyApplication.cpp
#include "MyApplication.h"
#include <QEvent>
#include <QDebug>
bool MyApplication::notify(QObject *o, QEvent *e)
{
if(this->topLevelWidgets().count()>0)
{
QWidget* mainWnd = this->topLevelWidgets().at(0);
if(o==(QObject*)mainWnd && e->type() == QEvent::MouseButtonPress)
{
// do ...
qDebug() << "mainwnd is clicked";
}
}
return QApplication::notify(o, e);
}
运行结果：
