18.QT-QPlainEdit 信号与槽

void appendHtml ( const QString & html )
void appendPlainText ( const QString & text )
void centerCursor ()
void clear ()
void copy ()
void cut ()
void insertPlainText ( const QString & text )
void paste ()
void redo ()
void selectAll ()
void setPlainText ( const QString & text )
void undo ()

void blockCountChanged ( int newBlockCount );
//每当按下回车或者删除回车(更新字符块),则newBlockCount计数,并触发该信号, newBlockCount 默认为1

void copyAvailable ( bool yes );
//选择某串文字时,则触发该信号,并设置yes为true,如果取消选择,也会触发该信号,设置 yes为false

void cursorPositionChanged ()
////每当光标的位置发生变化时，触发该信号

void redoAvailable ( bool available );
//当文本框为空,则会触发该信号,并设置available为false,因为该文本框没有数据,所以无法重做
//当用户向空文本框输入数据时,同样也会触发该信号,设置available为true,表示可以实现重做

void selectionChanged ();
//当鼠标点击文本框时,触发该信号

void textChanged ();
//每当文档的内容发生变化时,则触发该信号,可以用来判断输入的字符是什么

 

void undoAvailable ( bool available );
//当用户无法撤销时,便会触发该信号,并设置available为false
//当用户修改/写入文本框内容,便会触发该信号,并设置available为true,表示可以撤销

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QPlainTextEdit>
#include <QPushButton>
#include <QDebug>

class Widget : public QWidget
{
    Q_OBJECT

    QPlainTextEdit edit;
    QPushButton* Undo;
    QPushButton*  Redo;
    QPushButton* Cut;
    QPushButton* Copy;
    QPushButton* Paste;
    QPushButton* all;
    QPushButton* clear;

private slots:
    void       oncopyAvailable ( bool yes );
    void       onredoAvailable ( bool available );
    void       onundoAvailable ( bool available );
public:
    explicit Widget(QWidget *parent = 0);
};

#endif

#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);

    /*设置按键与文本框槽的关系*/
    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()));

    /*设置文本框信号与槽函数的关系*/
    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);
}