在实际的应用场景中，经常会出现软件界面战场图大于实际窗体大小，利用QScrollArea可以为widget窗体添加滚动条，可以实现小窗体利用滚动条显示大界面需求。实现如下：
QT创建一个qWidget界面
在ui界面中利用QT自带的widget控件布局一个如下图所示的层叠关系，widget_2界面大小需大于widget大小
界面布局好后，将widget_2提升为类，提升之前需为工程新添加一个设计界面类，添加完之后，将widget_2提升为类类名和前面新添加的设计界面类名一致
源码实现如下
patchwindow.h
#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_Hpatchwindow.cpp
#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());
}
}mainwindow.h
#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_Hmainwindow.cpp
#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);
}最终实现效果如下，可以通过滚轮滚动界面，也可以通过鼠标拖拽来实现界面拖拽效果：
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