Qt application on arm-linux flickers when show window

hello qter

qt version:4.8.6
platform information: x11,arm-linux(tk1)
demo code:
Widget::Widget(QWidget parent) : QWidget(parent), ui(new Ui::Widget)
{
ui->setupUi(this);
this->setPalette(QPalette(QColor(Qt::black)));
QPushButton button = new QPushButton("next",this);
connect(button,SIGNAL(clicked()),this,SLOT(onButtonClick()));

QDialog* dialog = new QDialog(this);
dialog->resize(size());
QWidget* topW = new QWidget(dialog);
QPushButton* button1 = new QPushButton("back",&dialog);
connect(button1,SIGNAL(clicked()),dialog,SLOT(accept()));
QVBoxLayout* lw = new QVBoxLayout;
lw->addWidget(topW);
lw->addWidget(button1);
dialog->setLayout(lw);
}

void Widget::onButtonClick()
{

dialog->exec();

}
when dialog show,there appear flicker obviously,in my pc/linux,it works well,
Does anyone know why?
thanks

SGaist

Hi and welcome to devnet,

Do you mean you have an X11 server running for your application ?

How are you launching your application ?

hello qter

thanks for you reply,
i launch it by connect the embedded machine with ssh

ssh ubuntu@192.168.0.1
./untitled

now,i have solve this problem by add one line code
QDialog* dialog = new QDialog(this);
dialog->setAttribute(Qt::WA_NoSystemBackground);//add this code

even though i don't know why it effected;
but now a new problem comes
in the real application(not demo),when run graphicsview.setViewport(new QGLWidget),flicker come out again and worse.if i replace 'new QGLWidget' by 'new QWidget',everything goes well. i'm consulting for information

SGaist

That only answer my question partially. Do you have an X server running ? Some desktop environment ?

hello qter

@SGaist yes, it has x11 server running for the application.