1.新建类TextEdit继承自QTextEdit；

2.重写event事件；

3.判断tab键按下，return false;

TextEdit::TextEdit(QWidget* paernt) : QTextEdit(parent)
{
}

bool TextEdit::event(QEvent* event)
{
    if(event->type() == QEvent::KeyPress)
    {
        QKeyEvent* keyEvent = (QKeyEvent*)event;
        if(keyEvent->key() == Qt::Key_Tab)
        {
            return false;
        }
    }
    return QTextEdit::event(event);
}