Hello.

Creating a QWidget and change its background colour works fine. But if I try the same with a custom widget which inherits for QWidget it won't work.

This is an minamal example which shows this behaviour:

Qt Code: 
  1. #ifndef MAINWINDOW_H
  2. #define MAINWINDOW_H
  3.  
  4. #include <QMainWindow>
  5.  
  6. namespace Ui {
  7. class MainWindow;
  8. }
  9.  
  10. class MyWidget : public QWidget
  11. {
  12. 	Q_OBJECT
  13.  
  14. 	public:
  15. 		explicit MyWidget(QWidget *parent = 0);
  16. };
  17.  
  18. class MainWindow : public QMainWindow
  19. {
  20. 	Q_OBJECT
  21.  
  22. 	public:
  23. 		explicit MainWindow(QWidget *parent = 0);
  24. 		~MainWindow();
  25.  
  26. 	private slots:
  27. 		void on_pushButton_clicked();
  28.  
  29. 	private:
  30. 		Ui::MainWindow *ui;
  31. 		QWidget *m_pMyWidget;
  32. };
  33.  
  34. #endif // MAINWINDOW_H
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Qt Code: 
  1. #include "mainwindow.h"
  2. #include "ui_mainwindow.h"
  3.  
  4. MyWidget::MyWidget(QWidget *parent) :
  5. 	QWidget(parent)
  6. {
  7.  
  8. }
  9.  
  10. MainWindow::MainWindow(QWidget *parent) :
  11.     QMainWindow(parent),
  12.     ui(new Ui::MainWindow)
  13. {
  14. 	ui->setupUi(this);
  15. }
  16.  
  17. MainWindow::~MainWindow()
  18. {
  19. 	delete ui;
  20. }
  21.  
  22. void MainWindow::on_pushButton_clicked()
  23. {
  24. 	//m_pMyWidget = new QWidget(this);		// <= Works !!!
  25. 	m_pMyWidget = new MyWidget(this);		// <= Does not work !!!
  26. 	m_pMyWidget->setGeometry(0,0,300,100);
  27. 	m_pMyWidget->setStyleSheet("background-color:black;");
  28. 	m_pMyWidget->show();
  29. }
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What am I doing wrong?