## 一、前言

相信各位CS结构开发的程序员，多多少少都遇到过需要美化界面的事情，一般都不会采用系统的标题栏，这样就需要无边框标题栏窗体，默认的话无边框的标题栏都不支持拉伸和拖动的，毕竟去掉了标题栏则意味着失去了系统的窗体的属性，拉伸和拖动都需要自己写代码去实现，网上有很多类似的开源的方案，我也看过不少，总体来说复杂了些，对于初学者来说有可能看的云里雾里的，比如边框四周八个方位都可以自由拉伸这块，我的思路是针对设定的八个方位的区域进行识别鼠标是否按下，按下的哪个部位则执行什么拉伸策略，鼠标移到哪个位置则对应改变鼠标指针形状，更浅显易懂一些，至于拖动移动，还可以设置拖动的标题栏的高度等。

主要功能：

1. 可以指定需要无边框的widget

2. 边框四周八个方位都可以自由拉伸

3. 可设置对应位置的边距,以便识别更大区域

4. 可设置是否允许拖动

5. 可设置是否允许拉伸

## 二、代码思路

bool FramelessWidget::eventFilter(QObject *watched, QEvent *event){    if (widget != 0 && watched == widget) {        if (event->type() == QEvent::Resize) {            //重新计算八个描点的区域,描点区域的作用还有就是计算鼠标坐标是否在某一个区域内            int width = widget->width();            int height = widget->height();            //左侧描点区域            rectLeft = QRect(0, padding, padding, height - padding * 2);            //上侧描点区域            rectTop = QRect(padding, 0, width - padding * 2, padding);            //右侧描点区域            rectRight = QRect(width - padding, padding, padding, height - padding * 2);            //下侧描点区域            rectBottom = QRect(padding, height - padding, width - padding * 2, padding);            //左上角描点区域            rectLeftTop = QRect(0, 0, padding, padding);            //右上角描点区域            rectRightTop = QRect(width - padding, 0, padding, padding);            //左下角描点区域            rectLeftBottom = QRect(0, height - padding, padding, padding);            //右下角描点区域            rectRightBottom = QRect(width - padding, height - padding, padding, padding);        } else if (event->type() == QEvent::HoverMove) {            //设置对应鼠标形状,这个必须放在这里而不是下面,因为可以在鼠标没有按下的时候识别            QHoverEvent *hoverEvent = (QHoverEvent *)event;            QPoint point = hoverEvent->pos();            if (resizeEnable) {                if (rectLeft.contains(point)) {                    widget->setCursor(Qt::SizeHorCursor);                } else if (rectRight.contains(point)) {                    widget->setCursor(Qt::SizeHorCursor);                } else if (rectTop.contains(point)) {                    widget->setCursor(Qt::SizeVerCursor);                } else if (rectBottom.contains(point)) {                    widget->setCursor(Qt::SizeVerCursor);                } else if (rectLeftTop.contains(point)) {                    widget->setCursor(Qt::SizeFDiagCursor);                } else if (rectRightTop.contains(point)) {                    widget->setCursor(Qt::SizeBDiagCursor);                } else if (rectLeftBottom.contains(point)) {                    widget->setCursor(Qt::SizeBDiagCursor);                } else if (rectRightBottom.contains(point)) {                    widget->setCursor(Qt::SizeFDiagCursor);                } else {                    widget->setCursor(Qt::ArrowCursor);                }            }            //根据当前鼠标位置,计算XY轴移动了多少            int offsetX = point.x() - lastPos.x();            int offsetY = point.y() - lastPos.y();            //根据按下处的位置判断是否是移动控件还是拉伸控件            if (moveEnable) {                if (pressed) {                    widget->move(widget->x() + offsetX, widget->y() + offsetY);                }            }            if (resizeEnable) {                if (pressedLeft) {                    int resizeW = widget->width() - offsetX;                    if (widget->minimumWidth() <= resizeW) {                        widget->setGeometry(widget->x() + offsetX, rectY, resizeW, rectH);                    }                } else if (pressedRight) {                    widget->setGeometry(rectX, rectY, rectW + offsetX, rectH);                } else if (pressedTop) {                    int resizeH = widget->height() - offsetY;                    if (widget->minimumHeight() <= resizeH) {                        widget->setGeometry(rectX, widget->y() + offsetY, rectW, resizeH);                    }                } else if (pressedBottom) {                    widget->setGeometry(rectX, rectY, rectW, rectH + offsetY);                } else if (pressedLeftTop) {                    int resizeW = widget->width() - offsetX;                    int resizeH = widget->height() - offsetY;                    if (widget->minimumWidth() <= resizeW) {                        widget->setGeometry(widget->x() + offsetX, widget->y(), resizeW, resizeH);                    }                    if (widget->minimumHeight() <= resizeH) {                        widget->setGeometry(widget->x(), widget->y() + offsetY, resizeW, resizeH);                    }                } else if (pressedRightTop) {                    int resizeW = rectW + offsetX;                    int resizeH = widget->height() - offsetY;                    if (widget->minimumHeight() <= resizeH) {                        widget->setGeometry(widget->x(), widget->y() + offsetY, resizeW, resizeH);                    }                } else if (pressedLeftBottom) {                    int resizeW = widget->width() - offsetX;                    int resizeH = rectH + offsetY;                    if (widget->minimumWidth() <= resizeW) {                        widget->setGeometry(widget->x() + offsetX, widget->y(), resizeW, resizeH);                    }                    if (widget->minimumHeight() <= resizeH) {                        widget->setGeometry(widget->x(), widget->y(), resizeW, resizeH);                    }                } else if (pressedRightBottom) {                    int resizeW = rectW + offsetX;                    int resizeH = rectH + offsetY;                    widget->setGeometry(widget->x(), widget->y(), resizeW, resizeH);                }            }        } else if (event->type() == QEvent::MouseButtonPress) {            //记住当前控件坐标和宽高以及鼠标按下的坐标            QMouseEvent *mouseEvent = (QMouseEvent *)event;            rectX = widget->x();            rectY = widget->y();            rectW = widget->width();            rectH = widget->height();            lastPos = mouseEvent->pos();            //判断按下的手柄的区域位置            if (rectLeft.contains(lastPos)) {                pressedLeft = true;            } else if (rectRight.contains(lastPos)) {                pressedRight = true;            } else if (rectTop.contains(lastPos)) {                pressedTop = true;            } else if (rectBottom.contains(lastPos)) {                pressedBottom = true;            } else if (rectLeftTop.contains(lastPos)) {                pressedLeftTop = true;            } else if (rectRightTop.contains(lastPos)) {                pressedRightTop = true;            } else if (rectLeftBottom.contains(lastPos)) {                pressedLeftBottom = true;            } else if (rectRightBottom.contains(lastPos)) {                pressedRightBottom = true;            } else {                pressed = true;            }        } else if (event->type() == QEvent::MouseMove) {            //改成用HoverMove识别        } else if (event->type() == QEvent::MouseButtonRelease) {            //恢复所有            pressed = false;            pressedLeft = false;            pressedRight = false;            pressedTop = false;            pressedBottom = false;            pressedLeftTop = false;            pressedRightTop = false;            pressedLeftBottom = false;            pressedRightBottom = false;            widget->setCursor(Qt::ArrowCursor);        }    }    return QObject::eventFilter(watched, event);}

## 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/)