Well then.
@pan : i added focus policy
and done somethings but thats have no effect.

i made it with QDialog base class. But with QMainWindows its not working. I'm tired.
I just open Qt Creator and create gui application, which is using QMainWindow base class.

mainwindows.cpp
Qt Code: 
  1. #include "mainwindow.h"
  2. #include <QDebug>
  3.  
  4. MainWindow::MainWindow(QWidget *parent) :
  5.         QMainWindow(parent), ui(new Ui::MainWindow)
  6. {
  7.     ui->setupUi(this);
  8.     this->setWindowFlags(Qt::Dialog);
  9.     this->setFocusPolicy(Qt::NoFocus);
  10.     ui->textEdit->setFocusPolicy(Qt::StrongFocus);
  11.     ui->textEdit->installEventFilter(this);
  12. }
  13.  
  14. bool MainWindow::catch_event(QObject *obj, QEvent *event)
  15. {
  16.     if (obj == ui->textEdit && event->type()==QEvent::KeyPress)
  17.         {
  18.             QKeyEvent *keyevent = static_cast<QKeyEvent*>(event);
  19.             qDebug() << "key event";
  20.             return QObject::eventFilter(obj,event);
  21.         }
  22.     return QObject::eventFilter(obj,event);
  23. }
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Problem is not solved but i'm tired about 2 days. I will do with QDialog class.

Thanks all...