Qt drawRect在后台 [英] Qt drawRect in background

问题描述

我想绘制滑块的背景。我试过这个，但颜色掩盖了整个滑块。这是一个继承的类QSlider

I want to paint the background of a slider. I tried this but the color covers up the whole slider. This is in an inherited class of QSlider

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();
}

推荐答案

widget可以设置样式表：

To set the background of a widget you could set the style sheet:

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

以下将设置小部件的背景，允许您执行更多操作：

The following will set the background of the widget, allowing you to do more:

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);    
}

和btw。您的示例代码的以下两行将产生警告：

And btw. the following two lines of your sample code will yield a warning:

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

也就是这个使用GCC：

Namely this one using GCC:

QPainter :: begin：绘制设备只能由一个画家在
a的时间绘制。

QPainter::begin: A paint device can only be painted by one painter at a time.

所以，请确保，如我在我的例子中，你要么做 QPainter painter / code>或 painter.begin（this）。

So make sure, as I do in my example, that you either do QPainter painter(this) or painter.begin(this).

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