18.QT-QPlainEdit 信号与槽

#include "Widget.h"

Widget::Widget(QWidget *parent) :
    QWidget(parent),
    edit(this)
{
    edit.setGeometry(0,0,280,300);

    Undo=new QPushButton("重做",this);
    Redo=new QPushButton("撤销",this);
    Cut=new QPushButton("剪切",this);
    Copy=new QPushButton("复制",this);
    Paste=new QPushButton("拷贝",this);
    all=new QPushButton("全选",this);
    clear=new QPushButton("删除",this);
    Undo->setGeometry(290,0,100,30);
    Redo->setGeometry(290,40,100,30);
    Cut->setGeometry(290,80,100,30);
    Copy->setGeometry(290,120,100,30);
    Paste->setGeometry(290,160,100,30);
    all->setGeometry(290,200,100,30);
    clear->setGeometry(290,240,100,30);
    Undo->setEnabled(false);
    Redo->setEnabled(false);
    Cut->setEnabled(false);
    Copy->setEnabled(false);

    
    connect(Undo, SIGNAL(clicked()) , &edit ,SLOT(undo()));
    connect(Redo, SIGNAL(clicked()) ,  &edit ,SLOT(redo()));
    connect(Cut, SIGNAL(clicked()) ,    &edit ,SLOT(cut()));
    connect(Copy, SIGNAL(clicked()) ,    &edit ,SLOT(copy()));
    connect(Paste, SIGNAL(clicked()) ,    &edit ,SLOT(paste()));
    connect(all, SIGNAL(clicked()) ,  &edit ,SLOT(selectAll()));
    connect(clear, SIGNAL(clicked()) ,  &edit ,SLOT(clear()));

    
    connect(&edit, SIGNAL(copyAvailable(bool)) , this ,SLOT(oncopyAvailable(bool)));
    connect(&edit, SIGNAL(redoAvailable(bool)) , this ,SLOT(onredoAvailable(bool)));
    connect(&edit, SIGNAL(undoAvailable(bool)) , this ,SLOT(onundoAvailable(bool)));
    connect(&edit, SIGNAL(selectionChanged()) , this ,SLOT(onselectionChanged()));

}

void    Widget::oncopyAvailable ( bool yes )
{
       Cut->setEnabled(yes);
       Copy->setEnabled(yes);
}

void    Widget::onredoAvailable( bool available )
{
       Redo->setEnabled(available);
}

void    Widget::onundoAvailable ( bool available )
{
       Undo->setEnabled(available);
}

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文章来源：https://www.cnblogs.com/lifexy/p/9003918.html