《Qt5学习笔记6》信号和槽的多种组合

Qt中的信号和槽机制非常灵活，并且允许像如下使用信号和槽机制：

1、一个信号可以和（一个或多个）信号连接

QObject::connect(lineEdit1, SIGNAL(textChanged(QString)), lineEdit2, SIGNAL(textChanged(QString)));

2、一个信号可以和（一个或多个）一个槽连接

QObject::connect(lineEdit1, SIGNAL(textChanged(QString)), lineEdit2, SLOT(setText(QString)));
QObject::connect(lineEdit1, SIGNAL(textChanged(QString)), lineEdit3, SLOT(setText(QString)));

3、（一个或多个）信号可以和一个槽连接

下面看个简单的程序：

#include <QApplication>
#include <QDialog>
#include <QLineEdit>
#include <QLabel>
#include <QHBoxLayout>
#include <QVBoxLayout>

int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QDialog *dialog = new QDialog;
dialog->setWindowTitle("Test for Signals&Slots of QT");

QLineEdit *lineEdit1 = new QLineEdit;
QLineEdit *lineEdit2 = new QLineEdit;
QLineEdit *lineEdit3 = new QLineEdit;
QLabel *label1 = new QLabel("LineEdit1:");
QLabel *label2 = new QLabel("LineEdit2:");
QLabel *label3 = new QLabel("LineEdit3:");
label1->setBuddy(lineEdit1);
label2->setBuddy(lineEdit2);
label3->setBuddy(lineEdit3);

//改变lineEdit1会改变lineEdit2和lineEdit3
QObject::connect(lineEdit1, SIGNAL(textChanged(QString)), lineEdit2, SLOT(setText(QString)));
QObject::connect(lineEdit1, SIGNAL(textChanged(QString)), lineEdit3, SLOT(setText(QString)));
//改变lineEdit2会改变lineEdit1和lineEdit3，但是2和3并没有直接连接，而是通过1间接连接
QObject::connect(lineEdit2, SIGNAL(textChanged(QString)), lineEdit1, SLOT(setText(QString)));

QHBoxLayout *topLayout = new QHBoxLayout;
topLayout->addWidget(label1);
topLayout->addWidget(lineEdit1);
QHBoxLayout *middleLayout = new QHBoxLayout;
middleLayout->addWidget(label2);
middleLayout->addWidget(lineEdit2);
QHBoxLayout *bottomLayout = new QHBoxLayout;
bottomLayout->addWidget(label3);
bottomLayout->addWidget(lineEdit3);
QVBoxLayout *mainLayout = new QVBoxLayout;
mainLayout->addLayout(topLayout);
mainLayout->addLayout(middleLayout);
mainLayout->addLayout(bottomLayout);

dialog->setLayout(mainLayout);
dialog->show();

return app.exec();
}

运行效果：



注释已经写得很清楚了。灵活地使用Qt的信号和槽机制，能够实现很复杂的功能。