QT5.12 Qwidget cannot get focus

[xixi_cly]

在按键机上使用qt测试按键，窗口无法获取焦点，按键不生效，是不是我的代码写的不对？

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    setFocusPolicy(Qt::StrongFocus);
    setFixedSize(800, 800);
    qDebug()<<"begin test"<<endl;
    btn = new QPushButton(tr("open"),this);
    if (hasFocus()) {
        qDebug() << "has focus" << endl;
    } else {
        qDebug() << "NO focus" << endl;
    }
}

Widget::~Widget()
{
}

void Widget::keyPressEvent(QKeyEvent *event) {
    qDebug()<<"try"<<endl;
    if(event->key() == Qt::Key_1) {
        qDebug()<<"press 1"<<endl;
        btn->move(50, 50);
        
        if (hasFocus()) {
            qDebug() << "has focus" << endl;
        } else {
            qDebug() << "NO focus" << endl;
        }
    }
}