簡述

大家在做Qt的時候，經常都會遇到自定義QWidget吧，但一旦實現後，有變的不可以拉伸了，今天我們就來做一個可拉伸的自定義QWidget並且可以移動

實現

#ifndef AUTOSIZEWIDGET_H
#define AUTOSIZEWIDGET_H

#include "basewidget.h"
//這是mainWindow的基類，繼承與QWidget，實現了可拉伸大小
enum Direction {
    UP, DOWN, LEFT, RIGHT, LEFTTOP, LEFTBOTTOM, RIGHTBOTTOM, RIGHTTOP, NONE
};
class AutoSizeWidget : public
 
 QWidget
{
    Q_OBJECT

public:
    AutoSizeWidget(QWidget *parent=0);
    ~AutoSizeWidget();
protected:
    void mouseMoveEvent(QMouseEvent *) override;
    void mousePressEvent(QMouseEvent *) override;
    void mouseReleaseEvent(QMouseEvent *) override;
private:
    void judgeRegionSetCursor(const
 
 QPoint&);
    const int Padding = 2;
    bool isLeftPressDown;  // 判斷左鍵是否按下
    QPoint dragPosition;   // 視窗移動拖動時需要記住的點 
    // 視窗大小改變時，記錄改變方向
    Direction dir;        
};

#endif // AUTOSIZEWIDGET_H

cpp檔案

#include "autosizewidget.h"

AutoSizeWidget::AutoSizeWidget(QWidget *parent)
    : QWidget(parent)
{
    isLeftPressDown = false
 
;
    dir = NONE;
    // 追蹤滑鼠
    this->setMouseTracking(true);
}
void AutoSizeWidget::judgeRegionSetCursor(const QPoint& currentPoint)
{
    // 獲取窗體在螢幕上的位置區域，tl為topleft點，rb為rightbottom點
    QRect rect = this->rect();
    QPoint tl = mapToGlobal(rect.topLeft());
    QPoint rb = mapToGlobal(rect.bottomRight());

    int x = currentPoint.x();
    int y = currentPoint.y();

    if (tl.x() + Padding >= x && tl.x() <= x && tl.y() + Padding >= y && tl.y() <= y) {
        // 左上角
        dir = LEFTTOP;
        this->setCursor(QCursor(Qt::SizeFDiagCursor));  // 設定滑鼠形狀
    }
    else if (x >= rb.x() - Padding && x <= rb.x() && y >= rb.y() - Padding && y <= rb.y()) {
        // 右下角
        dir = RIGHTBOTTOM;
        this->setCursor(QCursor(Qt::SizeFDiagCursor));
    }
    else if (x <= tl.x() + Padding && x >= tl.x() && y >= rb.y() - Padding && y <= rb.y()) {
        //左下角
        dir = LEFTBOTTOM;
        this->setCursor(QCursor(Qt::SizeBDiagCursor));
    }
    else if (x <= rb.x() && x >= rb.x() - Padding && y >= tl.y() && y <= tl.y() + Padding) {
        // 右上角
        dir = RIGHTTOP;
        this->setCursor(QCursor(Qt::SizeBDiagCursor));
    }
    else if (x <= tl.x() + Padding && x >= tl.x()) {
        // 左邊
        dir = LEFT;
        this->setCursor(QCursor(Qt::SizeHorCursor));
    }
    else if (x <= rb.x() && x >= rb.x() - Padding) {
        // 右邊
        dir = RIGHT;
        this->setCursor(QCursor(Qt::SizeHorCursor));
    }
    else if (y >= tl.y() && y <= tl.y() + Padding) {
        // 上邊
        dir = UP;
        this->setCursor(QCursor(Qt::SizeVerCursor));
    }
    else if (y <= rb.y() && y >= rb.y() - Padding) {
        // 下邊
        dir = DOWN;
        this->setCursor(QCursor(Qt::SizeVerCursor));
    }
    else {
        // 預設
        dir = NONE;
        this->setCursor(QCursor(Qt::ArrowCursor));
    }
}

void AutoSizeWidget::mouseReleaseEvent(QMouseEvent *event)
{
    if (event->button() == Qt::LeftButton) {
        isLeftPressDown = false;
        if (dir != NONE) {
            this->releaseMouse();
            this->setCursor(QCursor(Qt::ArrowCursor));
        }
    }
}
void AutoSizeWidget::mousePressEvent(QMouseEvent *event)
{
    switch (event->button()) {
    case Qt::LeftButton:
        isLeftPressDown = true;
        if (dir != NONE) {
            this->mouseGrabber();
        }
        else {
            dragPosition = event->globalPos() - this->frameGeometry().topLeft();
        }
        break;
    default:
        QWidget::mousePressEvent(event);
    }
}
void AutoSizeWidget::mouseMoveEvent(QMouseEvent *event)
{
    QPoint gloPoint = event->globalPos();
    QRect rect = this->rect();
    QPoint tl = mapToGlobal(rect.topLeft());
    QPoint rb = mapToGlobal(rect.bottomRight());

    if (!isLeftPressDown) {
        this->judgeRegionSetCursor(gloPoint);
    }
    else {

        if (dir != NONE) {
            QRect rMove(tl, rb);

            switch (dir) {
            case LEFT:
                if (rb.x() - gloPoint.x() <= this->minimumWidth())
                    rMove.setX(tl.x());
                else
                    rMove.setX(gloPoint.x());
                break;
            case RIGHT:
                rMove.setWidth(gloPoint.x() - tl.x());
                break;
            case UP:
                if (rb.y() - gloPoint.y() <= this->minimumHeight())
                    rMove.setY(tl.y());
                else
                    rMove.setY(gloPoint.y());
                break;
            case DOWN:
                rMove.setHeight(gloPoint.y() - tl.y());
                break;
            case LEFTTOP:
                if (rb.x() - gloPoint.x() <= this->minimumWidth())
                    rMove.setX(tl.x());
                else
                    rMove.setX(gloPoint.x());
                if (rb.y() - gloPoint.y() <= this->minimumHeight())
                    rMove.setY(tl.y());
                else
                    rMove.setY(gloPoint.y());
                break;
            case RIGHTTOP:
                rMove.setWidth(gloPoint.x() - tl.x());
                rMove.setY(gloPoint.y());
                break;
            case LEFTBOTTOM:
                rMove.setX(gloPoint.x());
                rMove.setHeight(gloPoint.y() - tl.y());
                break;
            case RIGHTBOTTOM:
                rMove.setWidth(gloPoint.x() - tl.x());
                rMove.setHeight(gloPoint.y() - tl.y());
                break;
            default:
                break;
            }
            this->setGeometry(rMove);
        }
        else {
            move(event->globalPos() - dragPosition);
            event->accept();
        }
    }
    QWidget::mouseMoveEvent(event);
}
AutoSizeWidget::~AutoSizeWidget()
{

}