Qt5学习笔记（消息过滤器）

1 HEADERS += 2     MyWidget.h
3 
4 SOURCES += 5     MyWidget.cpp
6 
7 QT += widgets gui

 1 #ifndef MYWIDGET_H
 2 #define MYWIDGET_H
 3 
 4 #include <QWidget>
 5 #include <QPushButton>
 6 class MyWidget : public QWidget
 7 {
 8     Q_OBJECT
 9 public:
10     explicit MyWidget(QWidget *parent = nullptr);
11     QPushButton* _button;
12     bool eventFilter(QObject *, QEvent *);//原型
13 signals:
14 
15 public slots:
16 };
17 
18 #endif // MYWIDGET_H

 1 #include "MyWidget.h"
 2 #include <QPushButton>
 3 #include <QEvent>
 4 MyWidget::MyWidget(QWidget *parent) : QWidget(parent)
 5 {
 6     QPushButton* button;
 7     button = new QPushButton("This button", this);
 8     connect(button, SIGNAL(clicked()), this, SLOT(close()));
 9 
10     _button = button;
11     /*button给自己安装了一个消息过滤器，经过button的消息，都先要调用它的过滤器eventFilter函数*/
12     button->installEventFilter(this);
13 }
14 
15 bool MyWidget::eventFilter(QObject *o, QEvent *e)//o谁的，e什么消息(对象，事件)
16 {
17 
18     //(对象，事件)
19     if (o == (QObject*)_button &&
20             (e->type() == QEvent::MouseButtonPress ||
21             e->type() == QEvent::MouseButtonRelease ||
22              e->type() == QEvent::MouseButtonRelease ))//截断,单击，双击，不发生反应
23     {
24         return true;
25     }
26 
27     return QWidget::eventFilter(o, e);
28 }
29 #include <QApplication>
30 int main(int argc, char* argv[])
31 {
32     QApplication app(argc, argv);
33 
34     MyWidget w;
35     w.show();
36 
37     return app.exec();
38 }