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