Qt drawRect在后台

Question

我想画一个滑块的背景.我尝试了这个,但颜色覆盖了整个滑块.这是一个继承的QSlider类

void paintEvent(QPaintEvent *e) {
  QPainter painter(this);
  painter.begin(this);
  painter.setBrush(/*not important*/);

  // This covers up the control. How do I make it so the color is in
  // the background and the control is still visible?
  painter.drawRect(rect()); 

  painter.end();
}

Answer 1

要设置窗口小部件的背景,您可以设置样式表:

theSlider->setStyleSheet("QSlider { background-color: green; }");

以下将设置窗口小部件的背景,允许您执行更多操作:

void paintEvent(QPaintEvent *event) {
  QPainter painter;
  painter.begin(this);
  painter.fillRect(rect(), /* brush, brush style or color */);
  painter.end(); 

  // This is very important if you don't want to handle _every_ 
  // detail about painting this particular widget. Without this 
  // the control would just be red, if that was the brush used, 
  // for instance.
  QSlider::paintEvent(event);    
}

顺便说一下.您的示例代码的以下两行将产生警告:

QPainter painter(this);
painter.begin(this);

即使用GCC的这个:

QPainter :: begin:绘画设备一次只能由一位画家绘画.

因此,正如我在我的例子中所做的那样,确保你做QPainter painter(this)或者做painter.begin(this).