在上章我们学习了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):
(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)
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();
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