一、前言
在音频开发中，窗体多半为半透明、圆角窗体，如下为Qt 5.5 VS2013实现半透明方法总结。
二、半透明方法设置
1、窗体及子控件都设置为半透明
1）setWindowOpacity(0.8);//参数范围为0-1.0，通过QSlider控件做成透明度控制条
2）无边框设置
setWindowFlags(Qt::FramelessWindowHint);3）窗体圆角设置
setAttribute(Qt::WA_TranslucentBackground);通过paintEvent绘制窗体背景色与圆角void Widget::paintEvent(QPaintEvent *event){QPainter painter(this);painter.setRenderHint(QPainter::Antialiasing); // 反锯齿;painter.setBrush(QBrush(QColor("#616F76"))); //窗体背景色painter.setPen(Qt::transparent);QRect rect = this->rect(); //rect为绘制大小rect.setWidth(rect.width() - 1);rect.setHeight(rect.height() - 1);painter.drawRoundedRect(rect, 15, 15); //15为圆角角度//也可用QPainterPath 绘制代替 painter.drawRoundedRect(rect, 15, 15);//QPainterPath painterPath;//painterPath.addRoundedRect(rect, 15, 15);//15为圆角角度//painter.drawPath(painterPath);QWidget::paintEvent(event);}2、通过图片贴图，设置局部透明
1）窗体设置
setAttribute(Qt::WA_TranslucentBackground);//背景半透明属性设置setWindowFlags(Qt::FramelessWindowHint);//无边框窗体设置2）采用样式加载图片
ui->m_BgWidget->setStyleSheet("background-image:url(:/images/bg.png);");
注意：m_BgWidget为窗体对象的子窗体，不能直接设置QWidget
3）效果图如下
3、通过paintEvent重绘背景色透明度
1）窗体属性设置
setAttribute(Qt::WA_TranslucentBackground);//背景半透明属性设置setWindowFlags(Qt::FramelessWindowHint);//无边框窗体设置m_BgColor = QColor("#616F76");//默认背景色m_BgColor.setAlphaF(0.8);this->setContextMenuPolicy(Qt::CustomContextMenu);connect(this, SIGNAL(customContextMenuRequested(const QPoint &)),this, SLOT(showContextMenuSlot(const QPoint &)));//右击出现菜单2）右击出现菜单
void Widget::showContextMenuSlot(const QPoint &pos){QAction *act = NULL;if(NULL == m_Menu){m_Menu = new QMenu();//菜单m_Actions.clear();//记录所有Actionact = m_Menu->addAction("1.0", this, SLOT(funcSlot()));m_Actions << act;act->setCheckable(true);act = m_Menu->addAction("0.8", this, SLOT(funcSlot()));m_Actions << act;act->setCheckable(true); //设置可选中act->setChecked(true); //设置被选中act = m_Menu->addAction("0.5", this, SLOT(funcSlot()));m_Actions << act;act->setCheckable(true);act = m_Menu->addAction("0.3", this, SLOT(funcSlot()));m_Actions << act;act->setCheckable(true);act = m_Menu->addAction("0.1", this, SLOT(funcSlot()));m_Actions << act;act->setCheckable(true);}m_Menu->exec(mapToGlobal(pos));//弹出菜单}3）选择菜单Action，修改背景颜色透明度
void Widget::funcSlot(){QAction *act = qobject_cast<QAction *>(sender());//获取选中的Actionif(act){double alpha = act->text().toDouble();m_BgColor.setAlphaF(alpha);//背景色透明度修改foreach(QAction *action, m_Actions)//去除其余选中，互斥{if(act != action)action->setChecked(false);}this->update();//刷新界面}}4）通过paintEvent重绘背景色
void Widget::paintEvent(QPaintEvent *event){QPainter painter(this);painter.setRenderHint(QPainter::Antialiasing); // 反锯齿;painter.setBrush(QBrush(m_BgColor));//修改后的背景色painter.setPen(Qt::transparent);QRect rect = this->rect(); //rect为绘制窗体大小rect.setWidth(rect.width() - 1);rect.setHeight(rect.height() - 1);painter.drawRoundedRect(rect, 15, 15);//15为圆角角度//也可用QPainterPath 绘制代替 painter.drawRoundedRect(rect, 15, 15);//QPainterPath painterPath;//painterPath.addRoundedRect(rect, 15, 15);//painter.drawPath(painterPath);QWidget::paintEvent(event);}5）效果如下
4、通过paintEvent采用Clear模式绘图，实现局部透明
1）窗体属性设置
m_Margin = 60;//各个绘制图形与边框的距离m_BgColor = QColor("#00BFFF");//窗体背景色installEventFilter(this);//事件过滤器，用于鼠标按下后界面移动setWindowFlags(Qt::FramelessWindowHint);//无边框窗体设置setAttribute(Qt::WA_TranslucentBackground);//背景半透明属性设置2）画笔属性设置
void Widget::paintEvent(QPaintEvent *){QPainter painter(this);painter.setPen(Qt::NoPen);painter.setBrush(m_BgColor);painter.drawRoundedRect(this->rect(), 15, 15);//设置整体窗体圆角为15°painter.setCompositionMode(QPainter::CompositionMode_Clear);//设置Clear绘图模式//绘制三角形drawTriangle(&painter);//绘制圆drawCircular(&painter);//绘制矩形drawRectangle(&painter);}3）绘制三角形
void Widget::drawTriangle(QPainter *painter){QPainterPath path;int width = this->width() / 2;int height = this->height() / 2;//顶点int topX = width / 2;int topY = m_Margin;//左下顶点int leftX = m_Margin;int leftY = height - m_Margin;//右下顶点int rightX = width - m_Margin;int rightY = height - m_Margin;path.moveTo(topX, topY);//起点path.lineTo(leftX, leftY);//画线段1path.lineTo(rightX, rightY);//画线段2path.lineTo(topX, topY);//画线段3painter->fillPath(path, QBrush(m_BgColor));//绘制三角形}4）绘制圆
void Widget::drawCircular(QPainter *painter){int width = this->width() / 2;int height = this->height() / 2;int x = width + width / 2;//X向坐标int y = height / 2; //Y向坐标int r = width / 2 - m_Margin;//第一个参数为中心点，r为x向、y向长度（不一致时可绘制椭圆）painter->drawEllipse(QPoint(x, y), r, r);}5）绘制矩形
void Widget::drawRectangle(QPainter *painter){int width = this->width() / 2;int height = this->height() / 2;int rectWidth = width - 2 * m_Margin;//矩形宽度int rectHeight = height - 2 * m_Margin;//矩形高度int rectX = width - rectWidth / 2;//矩形X向长度int rectY = height + m_Margin;//矩形Y向长度painter->drawRect(QRect(rectX, rectY, rectWidth, rectHeight));}