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3.QT事件处理，消息过滤器

發布時間：2024/9/27 c/c++ 18 豆豆

生活随笔收集整理的這篇文章主要介紹了 3.QT事件处理，消息过滤器小編覺得挺不錯的,現在分享給大家,幫大家做個參考.

1? 新建一個項目：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,因為它默認調用兩次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")); ??? //設置它為默認的焦點，當點擊tab鍵之后可以切換焦點 ??? button->setDefault(true); ? ??? // 鼠標不需要按下，mouseMove就能得到調用 ??? 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())); } ? //通過這一句實現點擊按鈕的時候獲得按鈕上的text()內容 void MyWidget::slotButtonClicked() { ??? QLineEdit* button = (QLineEdit*)sender(); ??? qDebug() << button->text(); } ? /* QApplication先得到->具體應該處理的窗口::event()->event()根據消息類型來調用具體的虛函數 */ /* 1）可以重載具體的虛函數，來實現對消息的響應 ?? 2）可以重載event函數，用來處理或者截取消息 */ ? /* 截取消息 */ bool MyWidget::event(QEvent *ev) { ??? // 鼠標消息被截斷 ?? // if(ev->type() == QEvent::MouseButtonPress) ???? //?? return true; ??? ev->accept(); ? ??? return QWidget::event(ev); } ? /** * @brief MyWidget::closeEvent 窗口關閉的事件 */ void MyWidget::closeEvent(QCloseEvent *) { ??? qDebug() << "closeEvent"; } ? void MyWidget::paintEvent(QPaintEvent *) { ??? QPainter p(this); ??? //通過下面的方式實現畫線 ??? p.drawLine(QPoint(0, 0), QPoint(100, 100)); } ? /** * @brief MyWidget::mousePressEvent 鼠標按下的事件 * @param ev */ void MyWidget::mousePressEvent(QMouseEvent *ev) { #if 0 ??? QPoint pt = ev->pos(); ??? qDebug() << pt; ??? //如果鼠標按下的是左鍵的處理 ??? if(ev->button() == Qt::LeftButton){} ? ??? //如果按下的Shift鍵了 ??? if(ev->modifiers() == Qt::ShiftModifier) ??? { ??????? qDebug() << "shift press"; ??? } #endif ??? //改進辦法：先判斷是否有左鍵，然后如果判斷是否還按了Ctrl鍵 ??? if(ev->button() == Qt::LeftButton) ??? { ??????? if(ev->modifiers() == Qt::ControlModifier) ??????? { ??????????? // handle with Control; ??????????? return; ??????? } ??????? // handle2 without control; ??? } else {} } ? /** * @brief MyWidget::mouseReleaseEvent 鼠標釋放的按鍵 */ void MyWidget::mouseReleaseEvent(QMouseEvent *){} ? /** * @brief MyWidget::mouseMoveEvent 鼠標移動的事件 */ void MyWidget::mouseMoveEvent(QMouseEvent *) { ??? static int i=0; ??? qDebug() << "mouse move"<< i++; } ? /** * @brief MyWidget::keyPressEvent 鼠標按下的事件，通過這個可以獲得按下的鍵 * @param ev */ void MyWidget::keyPressEvent(QKeyEvent *ev) { ??? ev->modifiers(); ??? int key = ev->key(); ??? qDebug() << key; ??? char a = key; ??? qDebug() << (char)a; } ? /** * @brief MyWidget::keyReleaseEvent 按鍵釋放的事件 */ void MyWidget::keyReleaseEvent(QKeyEvent *){} ? int main(int argc, char* argv[]) { ??? QApplication app(argc, argv); ? ??? MyWidget w; ??? w.show(); ? ??? return app.exec(); }

運行結果：

2? QT消息過濾器

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給自己安裝了一個消息過濾器，那么經過button的消息， ???? * 都先要調用它的過濾器的eventFilter函數*/ ??? 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(); ? ??? //發送一個Event給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); }

運行結果：

總結

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