插槽函数未被调用

#include <QApplication>
#include <QPushButton>
#include <QLabel>
#include <QDialog>
#include <QObject>
#include <QHBoxLayout>

int main(int argc, char ** argv)
{
   QApplication app(argc, argv);
   QDialog *dialog = new QDialog;
   QPushButton *testButton = new QPushButton(QObject::tr("test"));   
   QLabel * testLabel = new QLabel (QObject::tr("test"));
   QHBoxLayout * layout = new QHBoxLayout;
   layout->addWidget(testButton);
   layout->addWidget(testLabel);
   QObject::connect(testButton, SIGNAL(toggled(bool)), testLabel, SLOT(setVisible(bool)));
   dialog->setLayout(layout);
   dialog->show();
   return app.exec();
}

QObject::connect(testButton, SIGNAL(clicked(bool)), testLabel, SLOT(setVisible(bool))); 它使标签消失。

那么,为什么它不工作的信号“切换”。我猜,它找不到那个信号。你们能发光吗?