Qt入门（常用类、方法、信息槽）

常用类

QApplication a(argc, argv);

//实例化一个应用

QLabel label("Hello world");

//标签

QPushButton button("Quit");

//button

MainWindow b;b.show();

//窗口

常用方法

QObject::connect()有五个重载

QMetaObject::Connection connect(const QObject *, const char *,const QObject *, const char *,Qt::ConnectionType);

QMetaObject::Connection connect(const QObject *, const QMetaMethod &,const QObject *, const QMetaMethod &,Qt::ConnectionType);

QMetaObject::Connection connect(const QObject *, const char *,const char *,Qt::ConnectionType) const;

QMetaObject::Connection connect(const QObject *, PointerToMemberFunction,const QObject *, PointerToMemberFunction,Qt::ConnectionType)

QMetaObject::Connection connect(const QObject *, PointerToMemberFunction,Functor);

注：Functor类型：这个类型可以接受 static 函数、全局函数以及 Lambda 表达式。

2.

qDebug()<<""

//类似cout的标准输出

信息槽

信息槽机制，通过QObject::connect()函数实现。

自定义信息槽。

注意：（1）只有继承了QObject类的类，才具有信号槽的能力

（2）凡是QObject类（不管是直接子类还是间接子类），都应该在第一行代码写上Q_OBJECT，这个宏应该放在头文件中。

（3）实例

//!!! Qt5
#include <QObject>

////////// newspaper.h
class Newspaper : public QObject
{
Q_OBJECT
public:
Newspaper(const QString & name) :
m_name(name)
{
}

void send()
{
emit newPaper(m_name);
}

signals:
void newPaper(const QString &name);

private:
QString m_name;
};

////////// reader.h
#include <QObject>
#include <QDebug>

class Reader : public QObject
{
Q_OBJECT
public:
Reader() {}

void receiveNewspaper(const QString & name)
{
qDebug() << "Receives Newspaper: " << name;
}
};

////////// main.cpp
#include <QCoreApplication>

#include "newspaper.h"
#include "reader.h"

int main(int argc, char *argv[])
{
QCoreApplication app(argc, argv);

Newspaper newspaper("Newspaper A");
Reader reader;
QObject::connect(&newspaper, &Newspaper::newPaper,
&reader,    &Reader::receiveNewspaper);
newspaper.send();

return app.exec();
}