QWidget::setLayout: Attempting to set QLayout "" on MainWindow "", which already has a layout

如题，出现这个的原因是，如果你的窗口继承的是QMainwindow，需要设置

setCentralWidget（）;

如下：

     
     
     
     

      
      
      
      
 
       
 
        QWidget 
        * widget 
        = 
        new 
        QWidget 
        (mainWindow 
        ); 
       
 
      
      
      
      
 
       

         widget 
        ->setLayout 
        (gridLayout 
        ); 
       
 
      
      
      
      
 
       

         mainWindow 
        ->setCentralWidget 
        (widget 
        ); 
       
     
     
     
     
设置好一个widget即可



from:http://blog.csdn.net/zhuyingqingfen/article/details/6562246