Qt QScrollArea界面嵌套移动

#ifndef PATCHWINDOW_H
#define PATCHWINDOW_H

#include <QDebug>
#include <QPainter>
#include <QWidget>
#include <QMouseEvent>
#include <QStyleOption>
#include <QPaintEvent>

enum CursorRegion{
    NONE,
    TOPLEFT,
    TOPRIGHT,
    BOTTOMRIGHT,
    BOTTOMLEFT
};

namespace Ui {
class Patchwindow;
}

class Patchwindow : public QWidget
{
    Q_OBJECT

public:
    explicit Patchwindow(QWidget *parent = 0);
    ~Patchwindow();
    CursorRegion getCursorRegion(QPoint);

public:
    int borderWidth;
    int handleSize;

    bool mousePressed;
    QPoint previousPos;

private:
    Ui::Patchwindow *ui;

protected:
    void mousePressEvent(QMouseEvent*);
    void mouseReleaseEvent(QMouseEvent*);
    void mouseMoveEvent(QMouseEvent*);

signals:
    void send_widget_rx_ry(int rx,int ry);
};

#endif // PATCHWINDOW_H

#include "patchwindow.h"
#include "ui_patchwindow.h"

Patchwindow::Patchwindow(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Patchwindow)
{
    ui->setupUi(this);

    this->setMouseTracking(true);

    setFocusPolicy(Qt::StrongFocus);

    mousePressed = false;
    borderWidth = 1;
    handleSize = 8;

}

Patchwindow::~Patchwindow()
{
    delete ui;
}


//设置鼠标形状
CursorRegion Patchwindow::getCursorRegion(QPoint pos)
{
    if (pos.x() > 0 && pos.x() < (handleSize + borderWidth) &&
        pos.y() > 0 && pos.y() < (handleSize + borderWidth)  ){
        if (this->hasFocus())
            this->setCursor(QCursor(Qt::SizeFDiagCursor));
        return CursorRegion::TOPLEFT;
    }

    if (pos.x() > (this->width() - handleSize - borderWidth) && pos.x() < this->width() &&
        pos.y() > 0 && pos.y() < (handleSize + borderWidth)  ){
        if (this->hasFocus())
            this->setCursor(QCursor(Qt::SizeBDiagCursor));
        return CursorRegion::TOPRIGHT;
    }

    if (pos.x() > (this->width() - handleSize - borderWidth) && pos.x() < this->width() &&
        pos.y() > (this->height() - handleSize - borderWidth) && pos.y() < this->height()  ){
        if (this->hasFocus())
            this->setCursor(QCursor(Qt::SizeFDiagCursor));
        return CursorRegion::BOTTOMRIGHT;
    }


    if (pos.x() > 0 && pos.x() < (handleSize + borderWidth) &&
        pos.y() > (this->height() - handleSize - borderWidth) && pos.y() < this->height()  ){
        if (this->hasFocus())
            this->setCursor(QCursor(Qt::SizeBDiagCursor));
        return CursorRegion::BOTTOMLEFT;
    }

    this->setCursor(Qt::ArrowCursor);
    return CursorRegion::NONE;
}

void Patchwindow::mousePressEvent(QMouseEvent *event)
{
    mousePressed = true;
    previousPos = this->mapToParent(event->pos());
    //qDebug()<<"previousPos = "<<previousPos;
}

void Patchwindow::mouseReleaseEvent(QMouseEvent*)
{
    mousePressed = false;
}

void Patchwindow::mouseMoveEvent(QMouseEvent *event)
{
    if (mousePressed){
        QPoint _curPos = this->mapToParent(event->pos());
        QPoint _offPos = _curPos - previousPos;
        previousPos = _curPos;
        //qDebug()<<"_offPos = "<<_offPos;
        //qDebug()<<"_curPos = "<<_curPos;
        emit send_widget_rx_ry(_offPos.rx(),_offPos.ry());
    }
}

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QHBoxLayout>
#include <QDebug>
#include <QScrollArea>


namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

    QScrollArea *m_pScroll;


private:
    Ui::MainWindow *ui;

private slots:
    void remove_widget(int r_x,int r_y);


};

#endif // MAINWINDOW_H

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QPalette>

#include <QScrollBar>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    //this->resize(600,600);

    //给父窗体填充颜色
    QPalette palette = ui->widget_2->palette();
    palette.setBrush(QPalette::Window,QBrush(QColor(61,61,61)));
    ui->widget_2->setAutoFillBackground(true);
    ui->widget_2->setPalette(palette);

    ui->widget_2->setAttribute(Qt::WA_StyledBackground);
    ui->widget_2->setStyleSheet("QWidget{background: black}");

    ui->widget_3->setAttribute(Qt::WA_TransparentForMouseEvents, true);//设置该层鼠标事件透明，可以设置为显示层

    m_pScroll = new QScrollArea(ui->widget);
    m_pScroll->setWidget(ui->widget_2);//给widget_2设置滚动条
    //ui->widget_2->setMinimumSize(1500,1000);//这里注意，要比主窗体的尺寸要大，不然太小的话会留下一片空白

    QHBoxLayout *pLayout = new QHBoxLayout;
    pLayout->addWidget(m_pScroll);
    pLayout->setMargin(0);
    pLayout->setSpacing(0);
    ui->widget->setLayout(pLayout);

    connect(ui->widget_2,&Patchwindow::send_widget_rx_ry,this,&MainWindow::remove_widget);

}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::remove_widget(int r_x,int r_y)
{
    r_y = m_pScroll->verticalScrollBar()->value()-r_y;
    r_x = m_pScroll->horizontalScrollBar()->value()-r_x;

    if((0 < r_y) | (r_y == 0))
    {
        if(r_y > m_pScroll->verticalScrollBar()->maximum())
        {
            r_y = m_pScroll->verticalScrollBar()->maximum();
        }
    }
    else
    {
        r_y = 0;
    }

    if((0 < r_x) | (r_x == 0))
    {
        if(r_x > m_pScroll->horizontalScrollBar()->maximum())
        {
            r_x = m_pScroll->horizontalScrollBar()->maximum();
        }
    }
    else
    {
        r_x = 0;
    }

    m_pScroll->verticalScrollBar()->setValue(r_y);
    m_pScroll->horizontalScrollBar()->setValue(r_x);

}