3.QT事件处理，消息过滤器



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：