Qt-Slider实例

      接着上节的内容，我们还是按照既定的目标，在对控件完成简单的介绍后我们需要介绍一个综合的实例，这样有助于我们更好的将理论与实践结合起来。

本节将述的Slider包含两个类:

1.SliserGroup是用户自定义控件，继承于QGroupBox类. 其内部包含 QSlider 、QScrollBar 、QDial.

2.主窗口包含QStackWidget和QGroupBox，其中QStackWidget相当于一个容器来容纳SliderGroup，QGroupBox包含几个控件，这些控件控制类似滑块的控件的行为。

#include <QWidget>
#include <QLabel>
#include <QSpinBox>
#include <QCheckBox>
#include <QComboBox>
#include <QGroupBox>
#include <QStackedWidget>
#include <QGridLayout>
#include <QHBoxLayout>
#include <QGridLayout>

#include "slidersgroup.h"
namespace Ui {
class SliderWidget;
}

class SliderWidget : public QWidget
{
    Q_OBJECT

public:
    explicit SliderWidget(QWidget *parent = nullptr);
    ~SliderWidget();

private:
    Ui::SliderWidget *ui;
    QGroupBox *controlGroup;
    QLabel *minimumLabel;
    QLabel *maximumLabel;
    QLabel *currentLabel;
    QSpinBox *minimumSpinBox;
    QSpinBox *maximumSpinBox;
    QSpinBox *currentSpinBox;
    QCheckBox *invertedAppearance;
    QCheckBox *invertedKeyBindings;
    QComboBox *orientationCombo;

    QStackedWidget *stackWidget;
    SlidersGroup *horizontalSlider;
    SlidersGroup *verticalSlider;


};

#endif // SLIDERWIDGET_H

在其头文件中声明变量，可以看到horizontalSlider、verticalSlider两个私有成员，分别代表水平方向放置的组合slider和垂直方向放置的Slider。

minimumLabel = new QLabel(tr("M&inimum value:"));
minimumSpinBox = new QSpinBox();
minimumSpinBox->setRange(-100,100);
minimumLabel->setBuddy(minimumSpinBox);
invertedAppearance = new QCheckBox(tr("Inverted Appearance"));

maximumLabel = new QLabel(tr("M&aximum value:"));
maximumSpinBox = new QSpinBox();
maximumSpinBox->setRange(-100,100);
maximumLabel->setBuddy(maximumSpinBox);
invertedKeyBindings = new QCheckBox(tr("Inverted Key Bindings"));

currentLabel = new QLabel(tr("C&urrent value:"));
currentSpinBox = new QSpinBox();
currentLabel->setBuddy(currentSpinBox);

orientationCombo = new QComboBox();
orientationCombo->addItem(tr("Horizontal Slider"));
orientationCombo->addItem(tr("Vertical Slider"));

horizontalSlider = new SlidersGroup(Qt::Horizontal,tr("Horizontal"));
verticalSlider = new SlidersGroup(Qt::Vertical,tr("Vertical"));
stackWidget = new QStackedWidget();
stackWidget->addWidget(horizontalSlider);
stackWidget->addWidget(verticalSlider);

    connect(minimumSpinBox,QOverload<int>::of(&QSpinBox::valueChanged),horizontalSlider,&SlidersGroup::setMinimum);//当minmiSpinBox的值发生改变的时候需要设置sliderde最小值
    connect(minimumSpinBox,QOverload<int>::of(&QSpinBox::valueChanged),verticalSlider,&SlidersGroup::setMinimum);//同上，为什么要设置两次，是因为stackwidget中包含水平排列的SliderGroup和垂直放置的SliderGruop,所以需要同时更新

    connect(maximumSpinBox,QOverload<int>::of(&QSpinBox::valueChanged),horizontalSlider,&SlidersGroup::setMaximum);
    connect(maximumSpinBox,QOverload<int>::of(&QSpinBox::valueChanged),verticalSlider,&SlidersGroup::setMaximum);

    connect(horizontalSlider,&SlidersGroup::ValueChanged,currentSpinBox,&QSpinBox::setValue);
    connect(verticalSlider,&SlidersGroup::ValueChanged,currentSpinBox,&QSpinBox::setValue);

    connect(orientationCombo,QOverload<int>::of(&QComboBox::activated),stackWidget,&QStackedWidget::setCurrentIndex);//当切换方向是需要改变stackwidget中的内容，setCurrentIndex函数可以切换要显示的当前内容。

    connect(invertedAppearance,&QCheckBox::toggled,horizontalSlider,&SlidersGroup::invertAppearance);
    connect(invertedAppearance,&QCheckBox::toggled,verticalSlider,&SlidersGroup::invertAppearance);

    connect(currentSpinBox,QOverload<int>::of(&QSpinBox::valueChanged),horizontalSlider,&SlidersGroup::setValue);
    connect(currentSpinBox,QOverload<int>::of(&QSpinBox::valueChanged),horizontalSlider,&SlidersGroup::setValue);

    connect(invertedKeyBindings,&QCheckBox::toggled,horizontalSlider,&SlidersGroup::invertKeyBindings);
    connect(invertedKeyBindings,&QCheckBox::toggled,verticalSlider,&SlidersGroup::invertKeyBindings);

    QGridLayout *controlLayout = new QGridLayout();
    controlLayout->addWidget(minimumLabel,0,0);
    controlLayout->addWidget(minimumSpinBox,0,1);
    controlLayout->addWidget(invertedAppearance,0,2);
    controlLayout->addWidget(maximumLabel,1,0);
    controlLayout->addWidget(maximumSpinBox,1,1);
    controlLayout->addWidget(invertedKeyBindings,1,2);
    controlLayout->addWidget(currentLabel,2,0);
    controlLayout->addWidget(currentSpinBox,2,1);
    controlLayout->addWidget(orientationCombo,3,0,1,3);
    controlGroup->setLayout(controlLayout);

    QHBoxLayout *mainLayout = new QHBoxLayout();
    mainLayout->addWidget(controlGroup);
    mainLayout->addWidget(stackWidget);
    setLayout(mainLayout);

    minimumSpinBox->setValue(0);//设置当前值
    maximumSpinBox->setValue(100);//设置当前值
    currentSpinBox->setValue(5);//设置当前值

 SliderGruop.h如下：

#ifndef SLIDERSGROUP_H
#define SLIDERSGROUP_H

#include <QGroupBox>
#include <QSlider>
#include <QScrollBar>
#include <QDial>
#include <QBoxLayout>

class SlidersGroup : public QGroupBox
{
    Q_OBJECT
public:
    explicit SlidersGroup(Qt::Orientation Orientation,const QString &title,QWidget *parent = nullptr);

signals:
    void ValueChanged(int);
public slots:
public slots:
    void setValue(int value);
    void setMinimum(int value);
    void setMaximum(int value);
    void invertAppearance(bool invert);
    void invertKeyBindings(bool invert);
private:
    QSlider *slider;
    QScrollBar *scrollBar;
    QDial *dial;
};

#endif // SLIDERSGROUP_H

   SliderGruop.cpp如下：

#include "slidersgroup.h"

SlidersGroup::SlidersGroup(Qt::Orientation Orientation,const QString &title,QWidget *parent) :
    QGroupBox(title,parent)
{

    slider = new QSlider(Orientation);
    slider->setFocusPolicy(Qt::StrongFocus);
    slider->setTickPosition(QSlider::TicksBothSides);
    slider->setTickInterval(10);
    slider->setSingleStep(1);

    scrollBar = new QScrollBar(Orientation);
    slider->setFocusPolicy(Qt::StrongFocus);

    dial = new QDial();
    slider->setFocusPolicy(Qt::StrongFocus);

    //主要是构成一个消息循环，只要一个发生改变其余两个也同时发生改变
    connect(slider,&QSlider::valueChanged,scrollBar,&QScrollBar::setValue);
    connect(scrollBar,&QScrollBar::valueChanged,dial,&QDial::setValue);
    connect(dial,&QDial::valueChanged,slider,&QSlider::setValue);
    
    //当slider的值发生改变的时候更新currentSpinBox
    connect(slider,&QSlider::valueChanged,this,&SlidersGroup::ValueChanged);

    QBoxLayout::Direction direction;
    if(Orientation == Qt::Horizontal)
        direction = QBoxLayout::TopToBottom;
    else
        direction = QBoxLayout::LeftToRight;
    QBoxLayout *mainLayout = new QBoxLayout(direction);
    mainLayout->addWidget(slider);
    mainLayout->addWidget(scrollBar);
    mainLayout->addWidget(dial);
    setLayout(mainLayout);
}
//设置Slider的当前值，由于前面构成了消息的循环，只要一个发生改变其余的都会发生改变，这样处理比较简单，要不就需要写三个槽函数来分别处理对应的值的更新
void SlidersGroup::setValue(int value)
{
    slider->setValue(value);
}
//设置最大值
void SlidersGroup::setMinimum(int value)
{
    slider->setMinimum(value);
    scrollBar->setMinimum(value);
    dial->setMinimum(value);
}
//设置最小值
void SlidersGroup::setMaximum(int value)
{
    slider->setMaximum(value);
    scrollBar->setMaximum(value);
    dial->setMaximum(value);
}
//保留滑块是否反转显示其值，若invert为True最大值和最小值的位置发生调换，否则左边为最小值，右边为最大值
void SlidersGroup::invertAppearance(bool invert)
{
    slider->setInvertedAppearance(invert);
    scrollBar->setInvertedAppearance(invert);
    dial->setInvertedAppearance(invert);
}

void SlidersGroup::invertKeyBindings(bool invert)
{
    slider->setInvertedControls(invert);//此属性保留滑块是否反转其控制盘和关键点事件。若invert为false，则鼠标滚轮向上滑则slider值递增、pageup按钮按住其值也递增，否则相反
    scrollBar->setInvertedControls(invert);
    dial->setInvertedControls(invert);
}

效果图如下：