63.QT-重写QStackedWidget模仿iphone的home界面,实现左右滑动

在上章我们学习了62.QT-QScroller实现home界面滑动效果,但是该界面是实现的上下滑动效果,如果想模拟手机home滑动界面,则需要实现左右滑动效果.

本章,则重写QStackedWidget类,来真正的模拟手机,来实现home界面左右滑动效果.

1.SmoothStackedWidget类实现

demo界面如下图所示(创建了4个子界面):

效果图如下所示(支持快滑,慢滑):

如果是慢滑,则根据当前滑到的界面处于哪一页占比更多,则就跳到哪里.

否则就是快滑,根据滑动的偏移值来决定跳转

同样也支持边缘滑动检测(已在最边缘时,则滑动速率减慢,告诉用户已到边缘):

demo下载:https://download.csdn.net/download/qq_37997682/15450208

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2.代码实现

头文件如下所示：

#ifndef SMOOTHSTACKEDWIDGET_H
#define SMOOTHSTACKEDWIDGET_H

#include <QObject>
#include <QWidget>
#include <QStackedWidget>
#include <QAbstractScrollArea>
#include <QPixmap>
#include <QPropertyAnimation>

class SmoothStackedWidget : public QStackedWidget
{
    Q_OBJECT

#define SMOOTH_MAX_MS   900                   //平滑滑动时的最大延迟时间
#define SMOOTH_EDGE_MOVE_RATIO   0.14         //边缘移动系数,范围0~1,越低越慢

    typedef enum tagScrollMouseDragInfo {
          MOUSE_RELEASE = 0,                       //鼠标离开
          MOUSE_PRESS = 1,                         //按下
          MOUSE_PRESS_MOVE = 2,                    //按下移动
          MOUSE_RELEASE_MOVE = 3                   //鼠标离开并滑动
    }Scroll_Mouse_Drag_INFO_E;

    typedef enum tagSmoothAnimationSwitchInfo {
          SWITCH_PRE = -1,                      //切换上一页
          SWITCH_NONE = 0,                      //不切换
          SWITCH_NEXT = 1,                      //切换下一页
    }AnimationSwitch_Drag_INFO_E;

    Scroll_Mouse_Drag_INFO_E m_dragFlag = MOUSE_RELEASE;
    AnimationSwitch_Drag_INFO_E m_switchFlag = SWITCH_NONE;
  
    QWidget *m_parent;

    QWidget m_smoothWidget;

    int m_smoothCurrentIndex=-1;

    QPropertyAnimation *animation;

    float m_smoothMovePos;

    bool eventFilter(QObject *obj, QEvent *evt) override;

    void paintEvent(QPaintEvent *event) override;

    void resizeEvent(QResizeEvent *event) override;

    void SmoothLoadPixmap(bool isSmoothUpdate = false);
    void SmoothStartMove();

    void SmoothMove(int offset);

    void SmoothAnimationStart(int startPos, int endPos, int durationMs);

    void SmoothAnimationInit();

public:
    explicit SmoothStackedWidget(QWidget *parent = nullptr);

    int addWidget(QAbstractScrollArea *w);

    int addWidget(QWidget *w);

    void setCurrentIndex(int index);

    void removeWidget(QWidget *w);

    void IconUpdate();      //刷新页数标签

    void UpdateSmooth();

signals:

protected slots:
    void OnSmoothAnimationFinished();

};

#endif // SMOOTHSTACKEDWIDGET_H

其中eventFilter()函数如下所示:

当鼠标(手指)按下移动时,则调用SmoothMove(offset),通过offset来动态显示滑动的界面.

当鼠标(手指)松开后,则调用SmoothAnimationStart()来实现界面移动(到底是切换上一页、还是切换下一页、还是当前页).

bool SmoothStackedWidget::eventFilter(QObject *obj, QEvent *evt)
{
    QMouseEvent *mouse =  dynamic_cast<QMouseEvent *>(evt);
    QWidget *w =  dynamic_cast<QWidget *>(obj);

    static int pressPoint_x   = 0;          //按下的坐标
    static int dragPoint_x    = -1;         //拖动时的坐标
    static qint64 pressMSec ;

    if(mouse && w && animation->state() == QAbstractAnimation::Stopped)
    {
         if( mouse->type() ==QEvent::MouseButtonPress)    //首次按下
        {
           pressMSec = QDateTime::currentDateTime().toMSecsSinceEpoch();     //记录按下的时间
           dragPoint_x  = mouse->pos().x();               //当前坐标
           pressPoint_x = dragPoint_x;                    //按下的位置
           m_dragFlag = MOUSE_PRESS;
        }
         else if(mouse->type() == QEvent::MouseButtonRelease &&
                 m_dragFlag == MOUSE_PRESS)               //未移动
        {
           m_dragFlag = MOUSE_RELEASE;
        }
         else if(mouse->type() == QEvent::MouseMove &&
                 m_dragFlag == MOUSE_PRESS)               //初次滑动,判断移动阀值,避免误操作
        {
            if(qAbs(dragPoint_x - mouse->pos().x()) > 3)     //判断移动阀值,避免误操作
            {
               dragPoint_x = mouse->pos().x();
               SmoothStartMove();
               m_dragFlag = MOUSE_PRESS_MOVE;
            }
        }
         else if(mouse->type() == QEvent::MouseMove &&
                 m_dragFlag== MOUSE_PRESS_MOVE )             //正在滑动
        {
            int offset = ( mouse->pos().x() - dragPoint_x);
            SmoothMove(offset);
            dragPoint_x = mouse->pos().x();
        }
        else if(mouse->type() == QEvent::MouseButtonRelease &&
                m_dragFlag == MOUSE_PRESS_MOVE)               //滑动结束,启动平滑滑动
        {
             int durationMs= QDateTime::currentDateTime().toMSecsSinceEpoch()-pressMSec;
             SmoothAnimationStart(pressPoint_x,mouse->pos().x(),durationMs);
             m_dragFlag = MOUSE_RELEASE;
        }
    }

    return QWidget::eventFilter(obj,evt);
}

SmoothAnimationStart()函数如下所示:

void  SmoothStackedWidget::SmoothAnimationStart(int startPos, int endPos, int durationMs)
{
    int pixelPerSecond=qAbs(endPos - startPos)*1000/durationMs;       //计算每秒像素点
    m_switchFlag = SWITCH_NONE;
    int moveX = qAbs(m_smoothWidget.x());
    float temp = width()*0.5;
    int animationEndX;

    //慢速滑动(速度过慢||时间过长),则根据当前滑到哪里,就跳到哪里
    if(pixelPerSecond<300 || durationMs > 1000) {
        if(moveX < (temp)) {        //[0,width/2] = 上一页
            if(currentIndex()==0) {
                animationEndX = -width();
            } else {
                animationEndX = 0;
                m_switchFlag = SWITCH_PRE;
            }
        } else if(moveX < (temp*3)) {    //[width/2,width*3/2] = 当前一页
            animationEndX = -width();
        } else {
            if(currentIndex()==(count()-1)) {   //[width*3/2,width*2] = 下一页
                animationEndX = -width();
            } else {
                animationEndX = -width()*2;
                m_switchFlag = SWITCH_NEXT;
            }
        }

    } else {　　　　// 否则就是快速滑动
        if(startPos < endPos) { //向右滑动
            if(currentIndex()==0) {
                animationEndX = -width();
            } else {
                animationEndX = 0;
                m_switchFlag = SWITCH_PRE;
            }
        } else {         //向左滑动
            if(currentIndex()==(count()-1)) {
                animationEndX = -width();
            } else {
                animationEndX = -width()*2;
                m_switchFlag = SWITCH_NEXT;
            }
        }
    }

    //根据每秒滑动像素点,来计算滑动时长.
    int animationDuration = durationMs;
    float xOffsetRatio = qAbs(animationEndX - m_smoothWidget.x()) / (static_cast<float>(width())); //计算滑动占整屏比例

    if(animationDuration > (SMOOTH_MAX_MS * xOffsetRatio)) //滑动时间过大,则重置
        animationDuration = SMOOTH_MAX_MS * xOffsetRatio;


    animation->setDuration(animationDuration);
    animation->setStartValue(m_smoothWidget.geometry());
    animation->setEndValue(QRect(animationEndX, m_smoothWidget.y(), m_smoothWidget.width(), m_smoothWidget.height()));
    animation->start();
}