问题描述
我正在尝试开发一个自定义QProgressBar
,其外观如下图:
I'm trying to develop a custom QProgressBar
that will look like the following image :
我创建了一个扩展QProgressBar的类并实现了paintEvent():
I created a class that extends QProgressBar and implemented the paintEvent() :
void CircularProgressBar::paintEvent(QPaintEvent*) {
int progress = this->value();
int progressInDegrees = (double)(progress*360)/100;
int barWidth = 20;
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing, true);
painter.setPen(QPen(Qt::black, barWidth, Qt::SolidLine,Qt::RoundCap));
painter.drawArc(barWidth/2, barWidth/2, this->width() - barWidth, this->height() - barWidth,
90*16, progressInDegrees*-16);}
这对绘制圆形进度条非常有用,但是我对进度条的线性渐变颜色遇到了麻烦.我尝试使用QLinearGradient
对象创建QPen
,并尝试将QPainter
笔刷设置为QLinearGradient
对象,但是两种策略均无效.可以用QPainter
绘制具有线性渐变颜色的圆弧吗?
This works great to draw the circular progress bar, but I'm having trouble with the linear gradient color of the bar. I tried creating a QPen
with a QLinearGradient
object and I tried setting the QPainter
brush to a QLinearGradient
object, but neither strategy worked. Is it possible to draw an arc with QPainter
that has a linear gradient color?
推荐答案
我知道这是一个老问题,但几天前我遇到了,我想我有一个解决方案.您要创建一个圆锥形渐变并剪辑要用作圆形加载条的磁盘.这是一个示例:
I know this is an old question but I came across it some days ago and I think I have a solution. What you want is to create a conical gradient and clip the disk you want to use as circular loading bar. Here is an example:
widget.h:
#ifndef WIDGET_H
#define WIDGET_H
#include <QWidget>
class QPaintEvent;
class Widget : public QWidget
{
Q_OBJECT
public:
explicit Widget(QWidget *parent = 0);
~Widget();
void setLoadingAngle(int loadingAngle);
int loadingAngle() const;
void setDiscWidth(int width);
int discWidth() const;
protected:
void paintEvent(QPaintEvent *);
private:
int m_loadingAngle;
int m_width;
};
#endif // WIDGET_H
widget.cpp:
#include "widget.h"
#include <QPaintEvent>
#include <QPainter>
#include <QConicalGradient>
#include <QPen>
Widget::Widget(QWidget *parent) :
QWidget(parent),
m_loadingAngle(0),
m_width(0)
{
}
Widget::~Widget()
{
}
void Widget::setLoadingAngle(int loadingAngle)
{
m_loadingAngle = loadingAngle;
}
int Widget::loadingAngle() const
{
return m_loadingAngle;
}
void Widget::setDiscWidth(int width)
{
m_width = width;
}
int Widget::discWidth() const
{
return m_width;
}
void Widget::paintEvent(QPaintEvent *)
{
QRect drawingRect;
drawingRect.setX(rect().x() + m_width);
drawingRect.setY(rect().y() + m_width);
drawingRect.setWidth(rect().width() - m_width * 2);
drawingRect.setHeight(rect().height() - m_width * 2);
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing);
QConicalGradient gradient;
gradient.setCenter(drawingRect.center());
gradient.setAngle(90);
gradient.setColorAt(0, QColor(178, 255, 246));
gradient.setColorAt(1, QColor(5, 44, 50));
int arcLengthApproximation = m_width + m_width / 3;
QPen pen(QBrush(gradient), m_width);
pen.setCapStyle(Qt::RoundCap);
painter.setPen(pen);
painter.drawArc(drawingRect, 90 * 16 - arcLengthApproximation, -m_loadingAngle * 16);
}
main.cpp:
#include "widget.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
Widget w;
w.setDiscWidth(20);
w.setLoadingAngle(270);
w.show();
return a.exec();
}
结果是:
当然,这不是完整而精确的解决方案,但我认为这是实现所需目标所需要了解的一切.其余的细节并不难实现.
Of course, it is not the complete and exact solution but I think it is everything you need to know in order to achieve what you want. The rest are details not hard to implement.
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