Qt5学习笔记（消息基础）

 #include "MyWidget.h"
 #include <QApplication>
 #include <QEvent>
 #include <QDebug>
 #include <QMouseEvent>//子类
 #include <QKeyEvent>
 #include <QVBoxLayout>

 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"));
     //按钮接收键盘信息，而不仅是鼠标
     button->setDefault(true);//空格键
     this->setMouseTracking(true);//鼠标不需要按住，mouseMove就能得到调用

     connect(button, SIGNAL(clicked()), this, SLOT(slotButtonClicked()));//单击，接收信号
     connect(button2, SIGNAL(clicked()), this, SLOT(slotButtonClicked()));
 #endif
     lay->addWidget(edit = new QLineEdit());
     connect(edit, SIGNAL(returnPressed()),this ,SLOT(slotButtonClicked()));
 }
 void MyWidget::slotButtonClicked()//槽函数
 {
     //QPushButton* button =  (QPushButton*)sender();
     QLineEdit* button =  (QLineEdit*)sender();
     qDebug() << button->text();//可以知道那个按钮被操作
 }
 /* 任何信息都是QApplication先得到－》具体应该处理的窗口：：event()->event()根据信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) //重载event函数
 {
     /*
     if (ev->type() == QEvent::MouseButtonPress)  //
     {
         QMouseEvent* ev1 = (QMouseEvent*)ev;　//强制类型转换QEvent 转　QMouseEvent
         qDebug() << "mouse press";
     }
     */
     //if(ev->type() == QEvent::MouseButtonPress)//截断
     //    return true;
     ev->accept();

     return QWidget::event(ev);//父类的虚函数
 }

 void MyWidget::closeEvent(QCloseEvent *)//关闭窗口后发送
 {
     qDebug() << "closeEvent";
 }

 void MyWidget::mousePressEvent(QMouseEvent *ev)
 {
 #if 0
     QPoint pt = ev->pos();
     qDebug() << pt;
     if (ev->button() == Qt::LeftButton)
     {

     }
     if (ev->modifiers() == Qt::ShiftModifier)
     {
         qDebug() << "shift press";
     }
 #endif
     if(ev->button() == Qt::LeftButton)//左键
     {
         if (ev->modifiers()==Qt::ControlModifier)//ctrl
         {
             return;
         }
     }
     else
     {}
 }
 void MyWidget::mouseReleaseEvent(QMouseEvent *)
 {}
 void MyWidget::mouseMoveEvent(QMouseEvent *)
 {
     static int i = ;
     qDebug() << "mouse move"<<i++;
 }
 void MyWidget::keyPressEvent(QKeyEvent *ev)
 {
     ev->modifiers();
     int key = ev->key();
     qDebug() << key;
     char a = key;
     qDebug() << (char)a;
 }
 void MyWidget::keyReleaseEvent(QKeyEvent *)
 {}
 int main(int argc, char* argv[])
 {
     QApplication app(argc, argv);
     MyWidget w;
     w.show();

     return app.exec();
 }

 #ifndef MYWIDGET_H
 #define MYWIDGET_H

 #include <QWidget>
 #include <QPushButton>
 #include <QLineEdit>
 class MyWidget : public QWidget
 {
     Q_OBJECT
 public:
     explicit MyWidget(QWidget *parent = nullptr);

     /* widget's event handler (all event) */
     bool event(QEvent *);//函数原型

     void mousePressEvent(QMouseEvent *);
     void mouseReleaseEvent(QMouseEvent *);
     void mouseMoveEvent(QMouseEvent *);
     /*不要用*/
     //void mouseDoubleClickEvent(QMouseEvent *);

     void keyPressEvent(QKeyEvent *);
     void keyReleaseEvent(QKeyEvent *);

     void closeEvent(QCloseEvent *);

     //void showEvent(QShowEvent *);
     //void hideEvent(QHideEvent *);

     QPushButton* button;
     QLineEdit* edit;

 signals:

 public slots:
     void slotButtonClicked();
 };

 #endif // MYWIDGET_H

HEADERS += \
    MyWidget.h

SOURCES += \
    MyWidget.cpp

QT += widgets gui

一部分关于按钮消息，另一部分关于文本输入。