Qt Day 1: Signals and Slots

basic definition 

        The so-called signal slot is actually the observer mode. When an event occurs , for example, a button detects that it has been clicked, it emits a signal . This kind of sending has no purpose and is similar to broadcasting. If an object is interested in this signal, it will use the connect function , which means that it will bind the signal it wants to process to one of its own functions (called a slot) to process the signal . That is to say, when the signal is emitted, the connected slot function will be automatically called back . This is similar to the observer pattern: when an event of interest occurs, an operation will be automatically triggered.

Standard signals and slots 

First, the wizard creates a project

 implemented in the constructor

Implement signals and slots

connect(&b1, &QPushButton::pressed, this, &MainWidget::close);
    /* &b1: 信号发出者，指针类型
     * &QPushButton::pressed：处理的信号，  &发送者的类名::信号名字
     * this: 信号接收者
     * &MainWidget::close： 槽函数，信号处理函数  &接收的类名::槽函数名字
     */

 Custom slot

 /* 自定义槽，普通函数的用法
  * Qt5：任意的成员函数，普通全局函数，静态函数
  * 槽函数需要和信号一致（参数，返回值）
  * 由于信号都是没有返回值，所以，槽函数一定没有返回值
 */
    connect(b2, &QPushButton::released, this, &MainWidget::mySlot);
    connect(b2, &QPushButton::released, &b1, &QPushButton::hide);

/* 自定义的槽 在头文件mainwidget.h中 声明 */
void MainWidget::mySlot()
{
    b2->setText("123");
}

Custom signal to achieve two independent window conversions

Create new subwindow 

Customize signal and slot functions and implement them