Qt开源作品16-通用无边框拖动拉伸

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。
• 本开源项目已经成功升级到V2.0版本，分门别类，图文并茂，保你爽到爆。
• Qt开源武林秘籍开发经验，看完学完，20K起薪，没有找我！

1. 国内站点：https://gitee.com/feiyangqingyun/QWidgetDemo
2. 国际站点：https://github.com/feiyangqingyun/QWidgetDemo
3. 开源秘籍：https://gitee.com/feiyangqingyun/qtkaifajingyan
4. 个人主页：https://qtchina.blog.csdn.net/
5. 知乎主页：https://www.zhihu.com/people/feiyangqingyun/