qt Settext无法显示

void MainWindow::on_ButtonAdd_Print_clicked()
{
    QString strFN;
    QString strPN;
    QString strPST;
    QString strPFT;
    QTextStream streamFN {&strFN};
    QTextStream streamPN {&strPN};
    QTextStream streamPST {&strPST};
    QTextStream streamPFT {&strPFT};

    streamFN << ui->EditFN->text();
    streamPN << ui->EditPN->text();
    streamPST << ui->EditPST->text();
    streamPFT << ui->EditPFT->text();

    streamFN >> strFN;

    ui->EditPFT->setText(strFN);



}

按钮被按下之后EditPFT的文本没有改变，什么原因，需要怎么改？