Qt信號槽Lambda

一、總結

     1.Lambda表達式[](){}，配合信號與槽使用特別方便，C++11新標准  在.pro 文件里面添加  CONFIG += C++11  之后可以使用。

     2.[]這個方括號是用來傳遞外部變量的, 因為在匿名函數中是無法使用外部變量的, 只能通過方括號傳遞給他, 才能捕獲到. 比如我需要使用a這個變量,

       只需要在方括號中加入a即可:[a](){};但是如果要傳的變量很多, 一個個加到方括號里就太麻煩了, 這時我們可以使用 '=', 將外部所有局部變量、類中

       所有成員以值傳遞方式傳進來: [=] (). 但是通過這種方式傳遞進來的變量是只讀的, 不能修改;

     3.使用 this, 可以把類中所有成員以值傳遞方式傳遞進來;[this](){}

     4.使用 &, 把外部所有局部變量, 通過引用方式傳遞進來(不推薦, 容易出錯);

　 5.{}花括號內為匿名函數的邏輯代碼;

二、代碼

#ifndef TESTWIDGET_H
#define TESTWIDGET_H

#include <QObject>
#include <QWidget>
#include <QVBoxLayout>
#include <QCheckBox>
class TestWidget : public QWidget
{
    Q_OBJECT
public:
    explicit TestWidget(QWidget *parent = nullptr);

signals:

public slots:
    void doSomething(int num,bool checked);
private:
    void initUI();
};

#endif // TESTWIDGET_H

 

#include "testwidget.h"
#include <QDebug>
TestWidget::TestWidget(QWidget *parent) : QWidget(parent)
{
    initUI();
}
void TestWidget::initUI()
{
    QVBoxLayout *vLayout=new QVBoxLayout(this);
    for(int i=0;i<6;i++)
    {
        QCheckBox *chk=new QCheckBox(this);
        chk->setText(QString::number(i));
        connect(chk, &QCheckBox::clicked, [=](bool checked){
           
                doSomething(i,checked);
        });

        vLayout->addWidget(chk);
    }
    setLayout(vLayout);

}
void TestWidget::doSomething(int num, bool isOk)
{
     qDebug()<<"num:"<<num<<"isOk:"<<isOk;
}

 

多個信號對應一個槽函數

#ifndef LEDWIDGET_H
#define LEDWIDGET_H

#include <QWidget>
#include <QVBoxLayout>
#include <QHBoxLayout>
#include <QGroupBox>
#include <QGridLayout>
#include <QLabel>
#include <QLineEdit>
#include <QPushButton>
namespace Ui {
class LedWidget;
}

class LedWidget : public QWidget
{
    Q_OBJECT

public:

    enum ButtonType{
        HIGH_R,
        HIGH_G,
        HIGH_B,
        MIDDLE_R,
        MIDDLE_G,
        MIDDLE_B,
        LOW_R,
        LOW_G,
        LOW_B
    };
    explicit LedWidget(QWidget *parent = nullptr);
    ~LedWidget();
private slots:
    void slotClickedButton(ButtonType type);
private:
    Ui::LedWidget *ui;

    void initUI();
    QLabel *createLabelText(QString text);
    QPushButton * newButton(QString text);

};

#endif // LEDWIDGET_H

#include "ledwidget.h"
#include "ui_ledwidget.h"
#include <QDebug>
LedWidget::LedWidget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::LedWidget)
{
    ui->setupUi(this);
    initUI();
}

LedWidget::~LedWidget()
{
    delete ui;
}
void LedWidget::initUI()
{

    QGroupBox *gb=new QGroupBox(this);
    gb->setTitle("Led");

    QPushButton *pbHR=newButton("R");
    QPushButton *pbHG=newButton("G");
    QPushButton *pbHB=newButton("B");

    QPushButton *pbMR=newButton("R");
    QPushButton *pbMG=newButton("G");
    QPushButton *pbMB=newButton("B");

    QPushButton *pbLR=newButton("R");
    QPushButton *pbLG=newButton("G");
    QPushButton *pbLB=newButton("B");

    connect(pbHR,&QPushButton::clicked,[=](){slotClickedButton(HIGH_R);});
    connect(pbHG,&QPushButton::clicked,[=](){slotClickedButton(HIGH_G);});
    connect(pbHB,&QPushButton::clicked,[=](){slotClickedButton(HIGH_B);});

    connect(pbMR,&QPushButton::clicked,[=](){slotClickedButton(MIDDLE_R);});
    connect(pbMG,&QPushButton::clicked,[=](){slotClickedButton(MIDDLE_G);});
    connect(pbMB,&QPushButton::clicked,[=](){slotClickedButton(MIDDLE_B);});

    connect(pbLR,&QPushButton::clicked,[=](){slotClickedButton(LOW_R);});
    connect(pbLG,&QPushButton::clicked,[=](){slotClickedButton(LOW_G);});
    connect(pbLB,&QPushButton::clicked,[=](){slotClickedButton(LOW_B);});

    QGridLayout *gLayout=new QGridLayout();
    gLayout->addWidget(createLabelText("High:"),0,0);
    gLayout->addWidget(pbHR,0,1);
    gLayout->addWidget(pbHG,0,2);
    gLayout->addWidget(pbHB,0,3);


    gLayout->addWidget(createLabelText("Middle:"),1,0);
    gLayout->addWidget(pbMR,1,1);
    gLayout->addWidget(pbMG,1,2);
    gLayout->addWidget(pbMB,1,3);

    gLayout->addWidget(createLabelText("Low:"),2,0);
    gLayout->addWidget(pbLR,2,1);
    gLayout->addWidget(pbLG,2,2);
    gLayout->addWidget(pbLB,2,3);

    gb->setLayout(gLayout);

    QVBoxLayout *vLayoutMain=new QVBoxLayout(this);
    vLayoutMain->addWidget(gb);
    setLayout(vLayoutMain);

}
QLabel *LedWidget::createLabelText(QString text)
{
     QLabel *lbl=new QLabel(text,this);
     lbl->setMinimumSize(80,25);
     lbl->setMaximumSize(80,25);
     return lbl;
}

QPushButton *LedWidget::newButton(QString text)
{
    QPushButton * pb=new QPushButton(text,this);
    pb->setMinimumSize(30,30);
    pb->setMaximumSize(30,30);
    if(text=="R")
    {
       pb->setObjectName("pbRed");
    }
    else if(text=="G")
    {
        pb->setObjectName("pbGreen");
    }
    else if(text=="B")
    {
        pb->setObjectName("pbBlue");
    }
    return pb;

}
void LedWidget::slotClickedButton(LedWidget::ButtonType type)
{
  qDebug()<<type;
  if(type==HIGH_R)
  {

  }
  else if(type==HIGH_G)
  {

  }
  else if(type==HIGH_B)
  {

  }
  else if(type==MIDDLE_R)
  {

  }
  else if(type==MIDDLE_G)
  {

  }
  else if(type==MIDDLE_B)
  {

  }
  else if(type==LOW_R)
  {

  }
  else if(type==LOW_G)
  {

  }
  else if(type==LOW_B)
  {

  }
}