63.QT-重寫QStackedWidget模仿iphone的home界面,實現左右滑動

在上章我們學習了62.QT-QScroller實現home界面滑動效果,但是該界面是實現的上下滑動效果,如果想模擬手機home滑動界面,則需要實現左右滑動效果.

本章,則重寫QStackedWidget類,來真正的模擬手機,來實現home界面左右滑動效果.

1.SmoothStackedWidget類實現

demo界面如下圖所示(創建了4個子界面):

效果圖如下所示(支持快滑,慢滑):

如果是慢滑,則根據當前滑到的界面處於哪一頁占比更多,則就跳到哪里.

否則就是快滑,根據滑動的偏移值來決定跳轉

同樣也支持邊緣滑動檢測(已在最邊緣時,則滑動速率減慢,告訴用戶已到邊緣):

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

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2.代碼實現

頭文件如下所示：

#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                   //平滑滑動時的最大延遲時間
#define SMOOTH_EDGE_MOVE_RATIO   0.14         //邊緣移動系數,范圍0~1,越低越慢

    typedef enum tagScrollMouseDragInfo {
          MOUSE_RELEASE = 0,                       //鼠標離開
          MOUSE_PRESS = 1,                         //按下
          MOUSE_PRESS_MOVE = 2,                    //按下移動
          MOUSE_RELEASE_MOVE = 3                   //鼠標離開並滑動
    }Scroll_Mouse_Drag_INFO_E;

    typedef enum tagSmoothAnimationSwitchInfo {
          SWITCH_PRE = -1,                      //切換上一頁
          SWITCH_NONE = 0,                      //不切換
          SWITCH_NEXT = 1,                      //切換下一頁
    }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();      //刷新頁數標簽

    void UpdateSmooth();

signals:

protected slots:
    void OnSmoothAnimationFinished();

};

#endif // SMOOTHSTACKEDWIDGET_H

其中eventFilter()函數如下所示:

當鼠標(手指)按下移動時,則調用SmoothMove(offset),通過offset來動態顯示滑動的界面.

當鼠標(手指)松開后,則調用SmoothAnimationStart()來實現界面移動(到底是切換上一頁、還是切換下一頁、還是當前頁).

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

    static int pressPoint_x   = 0;          //按下的坐標
    static int dragPoint_x    = -1;         //拖動時的坐標
    static qint64 pressMSec ;

    if(mouse && w && animation->state() == QAbstractAnimation::Stopped)
    {
         if( mouse->type() ==QEvent::MouseButtonPress)    //首次按下
        {
           pressMSec = QDateTime::currentDateTime().toMSecsSinceEpoch();     //記錄按下的時間
           dragPoint_x  = mouse->pos().x();               //當前坐標
           pressPoint_x = dragPoint_x;                    //按下的位置
           m_dragFlag = MOUSE_PRESS;
        }
         else if(mouse->type() == QEvent::MouseButtonRelease &&
                 m_dragFlag == MOUSE_PRESS)               //未移動
        {
           m_dragFlag = MOUSE_RELEASE;
        }
         else if(mouse->type() == QEvent::MouseMove &&
                 m_dragFlag == MOUSE_PRESS)               //初次滑動,判斷移動閥值,避免誤操作
        {
            if(qAbs(dragPoint_x - mouse->pos().x()) > 3)     //判斷移動閥值,避免誤操作
            {
               dragPoint_x = mouse->pos().x();
               SmoothStartMove();
               m_dragFlag = MOUSE_PRESS_MOVE;
            }
        }
         else if(mouse->type() == QEvent::MouseMove &&
                 m_dragFlag== MOUSE_PRESS_MOVE )             //正在滑動
        {
            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)               //滑動結束,啟動平滑滑動
        {
             int durationMs= QDateTime::currentDateTime().toMSecsSinceEpoch()-pressMSec;
             SmoothAnimationStart(pressPoint_x,mouse->pos().x(),durationMs);
             m_dragFlag = MOUSE_RELEASE;
        }
    }

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

SmoothAnimationStart()函數如下所示:

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

    //慢速滑動(速度過慢||時間過長),則根據當前滑到哪里,就跳到哪里
    if(pixelPerSecond<300 || durationMs > 1000) {
        if(moveX < (temp)) {        //[0,width/2] = 上一頁
            if(currentIndex()==0) {
                animationEndX = -width();
            } else {
                animationEndX = 0;
                m_switchFlag = SWITCH_PRE;
            }
        } else if(moveX < (temp*3)) {    //[width/2,width*3/2] = 當前一頁
            animationEndX = -width();
        } else {
            if(currentIndex()==(count()-1)) {   //[width*3/2,width*2] = 下一頁
                animationEndX = -width();
            } else {
                animationEndX = -width()*2;
                m_switchFlag = SWITCH_NEXT;
            }
        }

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

    //根據每秒滑動像素點,來計算滑動時長.
    int animationDuration = durationMs;
    float xOffsetRatio = qAbs(animationEndX - m_smoothWidget.x()) / (static_cast<float>(width())); //計算滑動占整屏比例

    if(animationDuration > (SMOOTH_MAX_MS * xOffsetRatio)) //滑動時間過大,則重置
        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();
}