title: qt:: mouseDoubleClickEvent doesn't work when ui being set
body: <p>Okay, so the code is very short, seen below:</p>
  
  <pre><code>MainWindow::MainWindow() :
      QMainWindow(),
      ui(new Ui::MainWindow)
  {
      //ui-&gt;setupUi(this);
  }
  
  MainWindow::~MainWindow()
  {
      delete ui;
  }
  
  void MainWindow:: mouseDoubleClickEvent ( QMouseEvent * event )
  {
      cout &lt;&lt; "being double clicked" &lt;&lt; endl;
  }
  
  void MainWindow:: mousePressEvent(QMouseEvent *){
      cout &lt;&lt; "being clicked once " &lt;&lt; endl;
  }
  </code></pre>
  
  <p>the setupUi is being slashed, in this case the output is fine, when I double click, it displays the "being double clicked " message.</p>
  
  <p>However, !!! when I when I setup the ui, it stops working!! The message will no longer be displayed... !!!</p>
  
  <p>Can someone please explain why! Thank you very much, this is urgent!!!!!!!!!</p>