After setDefaultAction for a QToolButton and call setChecked, then checked status wrong

//out of the program
MainWindow::on_setTrueButton_clicked() start
check status: false
set checked true
check status: true
MainWindow::on_setTrueButton_clicked() over
"MainWindow::on_toolButton_clicked(1)"
Sender Btn cheacked status: true

//out of the program
"MainWindow::on_toolButton_clicked(1)"
Sender Btn cheacked status: true
MainWindow::on_setFalseButton_clicked()
checked status: true
set checked false
checked status: false
MainWindow::on_setFalseButton_clicked() over
"MainWindow::on_toolButton_clicked(0)"
Sender Btn cheacked status: false

//Here is the code
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    QAction * a = new QAction(this);
    a->setCheckable(true);
    ui->toolButton->addAction(a);
    ui->toolButton->setDefaultAction(a);
    ui->toolButton->setObjectName("A");
}

MainWindow::~MainWindow()
{
    delete ui;
}


void MainWindow::on_toolButton_clicked(bool checked)
{
    qDebug()<<QString("MainWindow::on_toolButton_clicked(%1)").arg(checked);
    QToolButton *senderBtn = (QToolButton *)sender();
    qDebug()<<"Sender Btn cheacked status:"<<senderBtn->isChecked();
}

void MainWindow::on_setTrueButton_clicked()
{
    qDebug()<<"MainWindow::on_setTrueButton_clicked() start";
    qDebug()<<"check status:"<<ui->toolButton->isChecked();
    ui->toolButton->setChecked(true);
    qDebug()<<"set checked true";
    qDebug()<<"check status:"<<ui->toolButton->isChecked();
    qDebug()<<"MainWindow::on_setTrueButton_clicked() over";
}

void MainWindow::on_setFalseButton_clicked()
{
    qDebug()<<"MainWindow::on_setFalseButton_clicked()";
    qDebug()<<"checked status:"<<ui->toolButton->isChecked();
    ui->toolButton->setChecked(false);
    qDebug()<<"set checked false";
    qDebug()<<"checked status:"<<ui->toolButton->isChecked();
    qDebug()<<"MainWindow::on_setFalseButton_clicked() over";
}