Qt开源作品25-电池电量控件

## 一、前言
现在这个时代，智能手机不要太流行，满大街都是，甚至连爷爷奶奶级别的人都会用智能手机，本次要写的控件就是智能手机中的电池电量表示控件，采用纯painter绘制，其实也可以采用贴图，我估计大部分手机上的都是采用贴图的形式，贴图有个好处就是程序员不用操心，drawimage即可，速度非常快。
至于本控件没有任何技术难点，就是自动计算当前设置的电量，根据宽度的比例划分100个等分，每个等分占用多少个像素，然后电量*该比例就是要绘制的电量的区域，可以设置报警电量，低于该变量整个电池电量区域红色显示。
**主要功能：**
1. 可设置开关按钮的样式 圆角矩形/内圆形/外圆形
2. 可设置选中和未选中时的背景颜色
3. 可设置选中和未选中时的滑块颜色
4. 可设置显示的文本
5. 可设置滑块离背景的间隔
6. 可设置圆角角度
7. 可设置是否显示动画过渡效果
## 二、代码思路
```c++
void Battery::paintEvent(QPaintEvent *)
{
//绘制准备工作,启用反锯齿
QPainter painter(this);
painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);
//绘制边框
drawBorder(&painter);
//绘制背景
drawBg(&painter);
//绘制头部
drawHead(&painter);
}
void Battery::drawBorder(QPainter *painter)
{
painter->save();
double headWidth = width() / 10;
double batteryWidth = width() - headWidth;
//绘制电池边框
QPointF topLeft(5, 5);
QPointF bottomRight(batteryWidth, height() - 5);
batteryRect = QRectF(topLeft, bottomRight);
painter->setPen(QPen(borderColorStart, 5));
painter->setBrush(Qt::NoBrush);
painter->drawRoundedRect(batteryRect, borderRadius, borderRadius);
painter->restore();
}
void Battery::drawBg(QPainter *painter)
{
painter->save();
QLinearGradient batteryGradient(QPointF(0, 0), QPointF(0, height()));
if (currentValue <= alarmValue) {
batteryGradient.setColorAt(0.0, alarmColorStart);
batteryGradient.setColorAt(1.0, alarmColorEnd);
} else {
batteryGradient.setColorAt(0.0, normalColorStart);
batteryGradient.setColorAt(1.0, normalColorEnd);
}
int margin = qMin(width(), height()) / 20;
double unit = (batteryRect.width() - (margin * 2)) / 100;
double width = currentValue * unit;
QPointF topLeft(batteryRect.topLeft().x() + margin, batteryRect.topLeft().y() + margin);
QPointF bottomRight(width + margin + 5, batteryRect.bottomRight().y() - margin);
QRectF rect(topLeft, bottomRight);
painter->setPen(Qt::NoPen);
painter->setBrush(batteryGradient);
painter->drawRoundedRect(rect, bgRadius, bgRadius);
painter->restore();
}
void Battery::drawHead(QPainter *painter)
{
painter->save();
QPointF headRectTopLeft(batteryRect.topRight().x(), height() / 3);
QPointF headRectBottomRight(width(), height() - height() / 3);
QRectF headRect(headRectTopLeft, headRectBottomRight);
QLinearGradient headRectGradient(headRect.topLeft(), headRect.bottomLeft());
headRectGradient.setColorAt(0.0, borderColorStart);
headRectGradient.setColorAt(1.0, borderColorEnd);
painter->setPen(Qt::NoPen);
painter->setBrush(headRectGradient);
painter->drawRoundedRect(headRect, headRadius, headRadius);
painter->restore();
}
```
## 三、效果图

## 四、开源主页
**以上作品完整源码下载都在开源主页，会持续不断更新作品数量和质量，欢迎各位关注。**
1. 国内站点：[https://gitee.com/feiyangqingyun/QWidgetDemo](https://gitee.com/feiyangqingyun/QWidgetDemo)
2. 国际站点：[https://github.com/feiyangqingyun/QWidgetDemo](https://github.com/feiyangqingyun/QWidgetDemo)
3. 个人主页：[https://blog.csdn.net/feiyangqingyun](https://blog.csdn.net/feiyangqingyun)
4. 知乎主页：[https://www.zhihu.com/people/feiyangqingyun/](https://www.zhihu.com/people/feiyangqingyun/)