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));}